Arc Flash Overview

Arc Flash Overview


Required Materials:



 Electrical Safety in the Workplace® and NFPA70E® are registered trademarks of the National Fire Protection Association, Quincy, MA.



M-S AMC educational resources are in no way meant to be a substitute for occupational safety and health standards. No guarantee is made to resource thoroughness, statutory or regulatory compliance, and related media may depict situations that are not in compliance with OSHA and other safety requirements. It is the responsibility of educators/employers and their students/employees, or anybody using our resources, to comply fully with all pertinent OSHA, and any other, rules and regulations in any jurisdiction in which they learn/work. M-S AMC will not be liable for any damages or other claims and demands arising out of the use of these educational resources. By using these resources, the user releases the Multi-State Advanced Manufacturing Consortium and participating educational institutions and their respective Boards, individual trustees, employees, contractors, and sub-contractors from any liability for injuries resulting from the use of the educational resources.


"This product was funded by a grant awarded by the U.S. Department of Labor's Employment and Training Administration. The product was created by the grantee and does not necessarily reflect the official position of the U.S. Department of Labor. The Department of Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with respect to such information, including any information on linked sites and including, but not limited to, accuracy of the information or its completeness, timeliness, usefulness, adequacy, continued availability, or ownership.


M-S AMC resources reflect a shared understanding of grant partners at the time of development. In keeping with our industry and college partner requirements, our products are continuously improved. Updated versions of our work can be found here:

What it is

An arcing fault is the flow of current through the air between phase conductors or between conductors and a neutral or ground.


An arcing fault can be caused by any number of things, ranging from faulty panel wiring to simply dropping a screwdriver or other tools inside a live panel.


The energy that results from an arcing fault manifests as an arc flash, an arc blast or a combination of the two.

Figure 1: Arc Blast!

Courtesy of Westex® by Milliken®

What does ARC Flash/Blast Consist of?

  • Heat (up to 35,000 °F (19,500 °C) - more than three times the temperature at the photosphere - the visible surface of the sun)
  • Vaporized Copper - Toxic, expands 67,000 times in less than 1/1000th of a second.
  • Light - Intense UV and IR light waves
  • Pressure (can be higher than 2,000 lbs./sq. ft., lung damage threshold is 1728~2160 lbs./sq. ft.)
  • Sound (can exceed 140 dB, pain threshold is 125 dB)
  • Projectiles (shrapnel, molten metal)


Video 1: Arc Flash/Blast Animation

Why are Arcing Faults Dangerous?

The energy that results from an arcing fault manifests as an arc flash, an arc blast or a combination of the two.


Arc flash is exposure to the tremendous thermal energy released by an arc fault, which results in a variety of serious injuries and in some cases death.

The temperature at the center of an arc fault can reach nearly 35,000 °F. At these temperatures, typical conductors, like copper, are converted from a solid, to molten metal, to a vapor in less than a thousandth (<1/10000) of a second. As a comparison, the surface of the sun is about 9,940 ºF.

As a result, the vapor can expand to nearly 67,000 times the volume of the solid, superheating the surrounding air almost immediately. The expansion of this vapor, along with the rapid vaporization of conductors, results in an explosion of concussive forces. Additional injury may occur from falls if the person affected is working at elevation, on a platform, walkway or ladder.

If unprotected, this heat is capable of producing incurable third degree burns instantaneously. Electrical burns are typically slow to heal and frequently result in amputation.

In addition, this heat can ignite clothing at distances of ten feet or more, presenting an additional hazard as a result workers have been injured even though they were ten feet or more away from the arc center.


Arc blast is exposure to the pressure blast released by an arc fault. This blast can also cause shrapnel to be hurled at high velocity, which can cause serious injuries or death.


Between all of this, an arcing fault has the potential to damage a person's sight, hearing, lungs, skeletal system, respiratory system, muscular system and nervous system in addition to burn injuries.

  • What do you see
    • Very bright flash of light
  • What do you hear
    • Loud arcing or boom
  • What do you smell
    • Heavy ozone odor

View Video 1 to see an actual arc flash/blast demonstration from Westex® by Milliken®.


Video 1: Electrical Arc Flash Demonstration

Courtesy of Westex® by Milliken®



Figure 1: The Sun's Surface Temperature is About 10,000 Degrees Fahrenheit

Credit: NASA/SDO

Causes of Arc Flash

An arc flash can be spontaneous or result from inadvertently bridging electrical contacts with a conducting object. Other causes may include dropped tools or the buildup of conductive dust or corrosion. An electric arc flash can occur if a conductive object gets too close to a high-amp current source or by equipment failure (for instance, while opening or closing disconnects).

Conditions under which arc flash can occur:

Human Error, which is considered the most common cause:

  • Dropped or unintentional contact with live circuit with non-insulated tool or conductive object
  • Improper installation of equipment
  • Negligent or improperly done preventive maintenance
  • Failure to de-energize equipment whenever possible

Equipment Failure:

  • Due to failure of electrical equipment and or system design
  • Due to faulty system design


  • Buildup of conductive dust
  • Corrosion
  • Moisture or conductive liquids/vapor
  • Animal contact (rodent, snake, bird, etc.)


A worker was injured while laying block for a surface electrical installation. He was cleaning the mortar joints with a piece of metal conduit when the conduit fell through the top of a 660 VAC panel, causing a short. The ensuing arc burned through the panel access door (Figure 1), the flash inflicting 1st and 2nd degree burns to the worker's arm, face and neck.


Figure 1: Arc Blast Damage in Electrical Cabinet Door 


NIOSH Arc Flash Awareness

The National Institute for Occupational Safety and Health (NIOSH) produced a video (Video 1) of three electricians tell their story of being exposed to an arc flash and the effect on their lives.


Points of discussion questions to follow.


Video 1: ARC FLASH AWARENESS video provided by CDC & NIOSH

Video Discussion Questions

Optional to discuss as a group or self-examination.

If one of the incidents in the video had happened to you, how would it have changed your life or the life of your family?


Have you ever experienced an arc flash? What happened? Did you change any safety practices in your work after the incident? What were they?


What are some behaviors that you can change to help prevent an arc flash incident to yourself and/or to your fellow electricians?


What are some of the excuses electricians use for not wearing appropriate PPE?


In general, as electricians become more experienced, do you think their safety habits change? How?


After viewing this video, which, if any, of your own safety work habits would you like to change?


Do you have any suggestions for your supervisor that you feel could help prevent an arc flash incident from happening to you or any of your coworkers?


What suggestions do you have for your company to help prevent arc flash incidents?

Figure 1: Arc Flash Awareness Electricians


Arc Flash Statistic

According to data from National Fire Protection Association, the National Safety Council, and the Bureau of Labor Statistics, 10 arc flash accidents happen every day in the U.S. – and more than 3,600 disabling electrical contact injuries happen every year.


 Video 1 shows an actual arc flash/blast incident involving two electrical workers.

Video 1: Arc Flash Accident While Racking a Breaker

Regulatory Agencies

There are thousands of standards, regulations, specifications and guidelines developed by many dedicated people through various organizations to promote electrical safety including:

OSHA (Occupational Safety and Health Administration)

The Occupational Safety and Health Act of 1970, Congress created the Occupational Safety and Health Administration (OSHA)* to assure safe and healthful working conditions for working men and women by setting and enforcing standards and by providing training, outreach, education and assistance.

As a result, established the standards for electrical safe work practices as specified in OSHA 29 CFR 1910.331-.335 (Subpart S).

NFPA (National Fire Protection Association)

The NFPA is the worldwide leader and provider of standards regarding fire, electrical, building, and life safety. Since 1976, National Fire Protection Association has worked with the Occupational Safety and Health Administration (OSHA) to prepare standards to support the Occupational Safety and Health Act of 1970.

The NFPA publishes two widely followed standards, the NFPA 70®, known as the National Electrical Code® (NEC®). And the second, the NFPA 70E®, Standard for Electrical Safety Requirements for Employee Workplaces®, which was first published in 1979, and is revised— then republished every three years with the current issue, NFPA 70E 2015 Edition.


Though OSHA does not, per se, enforce NFPA 70E Standard, OSHA considers the NFPA Standard a recognized industry practice.

NIOSH (National Institute for Occupational Safety and Health)

The National Institute for Occupational Safety and Health (NIOSH) is the U.S. federal agency that conducts research and makes recommendations to prevent worker injury and illness. The Occupational Safety and Health Act of 1970 established NIOSH. NIOSH partners with the Occupational Safety and Health Administration (OSHA). OSHA is part of the U.S. Department of Labor, and it develops and enforces workplace safety and health regulations. NIOSH is part of the U.S. Centers for Disease Control and Prevention, in the U.S. Department of Health and Human Services. It has the mandate of helping to assure "every man and woman in the Nation safe and healthful working conditions and to preserve our human resources." NIOSH records and tracks electrical and arc flash related incidents.

ANSI (American National Standards Institute)

ANSI is a non-government, not-for-profit organization which facilitates the creating, conformity and use of voluntary consensus standards use in numerous business sectors to help insure the safety and health of workers and consumers. The U.S. government has authorized ANSI with the authorization to identity American Nation Standards, however does not write the standards.

One such standard is the ANSI Z535 Safety Alerting Standards which is composed of six sub-standards including the Z535.4, Product Safety Signs and Labels that provides guidelines for the design and uniformity of safety signs and labels for arc flash applications. ANSI also provides standards for PPE (Personal Protection Equipment) used for arc flash.

IEEE (Institute of Electrical and Electronic Engineers, Inc.)

The largest association of electrical, electronic engineering, telecommunications and computer science and information engineering professionals. It is a non-profit, non-government organization dedicated to providing standards for scientific and education purposes.

Publishes the IEEE Standard 1584, Guide for Performing Arc Flash Hazard Calculations, a calculation method providing definitive steps to support the NFPA 70E as well as case histories and analysis information.

American Society for Testing and Materials (ASTM)

Currently referred to as the ASTM International, this organization is a global leader in developing and delivery of voluntary, consensus-based standards. They provide test methods, specifications and guidance in improving product quality and safety. They have provided many standards used for the testing and analysis of the textiles used in Personal Protective Equipment adopted by ANSI.

One of the standards used to ensure worker safety is ASTM F1506: Standard Performance Specification for Flame Resistant and Arc Rated Textile Materials for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electric Arc and Related Thermal Hazards.


Figure 1: A Worker Engulfed by Arc Flash-Blast



Affected Employee - Non-qualified employee trained to work on affected piece of machinery or equipment, but not on electrical devices or energized parts such as a machine operator, production line worker or cleaning maintenance worker.


ARC Flash/Blast - An arc flash is the light and heat energy from ranging from far infrared to ultraviolet that is generated from an arc fault event due the flow of electrical current outside of its normal path. Arc flash may also be referred to as "flashover". The light energy is sufficient enough to ignite combustible materials, burn unprotected skin and cause permanent blindness. The arc blast of the arc fault event is the subsequent pressure wave created by the rapid heating of the conductive materials causing them to melt, vaporize, and expand the surrounding air.


Arc Rated (AR) - Arc Rating measures the insulating properties if Flame Resistant (FR) fabric/materials to Arc Flash. Arc Rated PPE is Flame Resistant PPE that has been tested to arc flash conditions with sensors measuring the heat transfer through the fabric. Calculations determine the energy transfer that would probably result in a 2nd degree burn through the fabric 50% of the time and expressed as a number in calories/cm2. Note that all clothing that is Arc Rated is also Flame Resistant but not all FR PPE is arc rated. The label should indicate that the garment complies with the applicable American Society of Testing and Materials standard. Note: The higher the Arc Rating value, the greater the protection.


Balaclava (Sock Hood) - An arc-rated hood made of fire resistant material that helps protects the neck and head. It has an opening for the for the eyes and nose facial area which is therefore not protected by the hood.


Barricades/Barriers - A physical obstruction such as tapes, cones, or A-frame type wood or metal structures intended to provide a warning about and to limit access to a hazardous area. A physical obstruction which is intended to prevent contact with energized lines or equipment or to prevent unauthorized access to a work area.


Circuit - A complete path for the flow of current.


Circuit Breaker - An overcurrent protection device that automatically shuts off the current in a circuit if an overload occurs.


Current Limiting Fuse - A type of fuse that very quickly introduces a high level of resistance once the device's current responsive element is melted by current flow as specified by the fuse's current limiting range, thus reducing the current's magnitude/duration and results in current fault interruption.


Conductor - Any material that has a low level of resistance, allowing the flow of electrons. This may include metals such as aluminum, copper and steel, to name a few, as well as materials with high moisture content, such as water, concrete and even air. Note: Distilled (de-ionized water itself is a good insulator; however, water that has any dissolved substances in it becomes conductive, even with a small amount of material creating an ion imbalance.


De-energized State - A device is in a de-energized state when disconnected from a source of electrical current and free of potential or stored electrical energy. Note that even though an electrical device may have had the power source removed; there may be residual energy present. Only a qualified worker with proper electrical training and equipment is qualified to determine the status of a device.


Electricity - The flow of energy in the form of electrons as through a conductor or across the gap between conductors.


Energized State - A device is in a energized state when connected to an source of electrical current, or stored (potential) electrical energy.


Energy Control and Power Lockout (ECPL) - Also referred to as "Lockout/Tagout" or LOTO - these are specific practices and procedures to follow to ensure employee safety when working on machinery to prevent accidental or unexpected energizing or start-up. An individual disconnects the equipment from its energy sources and any individual authorized to work on the machinery/equipment places their own lock or tag on the energy isolating device. The equipment is then verified that the machine/equipment is de-energized. This lesson may refer to ECPL but does not cover the subject.


Energy Isolating Device - A physical device that prevents the transmission or release of energy, including, but not limited to, the following: a manually operated electric circuit breaker, a disconnect switch, a manually operated switch, a slide gate, a slip blind, a line valve, blocks, and any similar device with a visible indication of the position of the device. (Push buttons, selector switches, and other control-circuit-type devices are not energy isolating devices.)


Fire Resistant (FR) - Typically refers to clothing that is flame resistant or flame-retardant-treated, when exposed to flames or electric arcs, would not increase the extent of injury that would be sustained by the employee. First, FR resists ignition from the initial arc flash, secondly FR insulates the wearer from thermal injury.


Ground - A large conducting body (such as the earth) used as a common return for an electric circuit and as an arbitrary zero of potential.


Ground Fault - A loss of current from a circuit to a ground connection.


Ground Fault Interruption Device (GFID) - A device that functions to de-energize a circuit or portion of a circuit for the protection of personnel within an established period of time when the current to ground exceeds a predetermined value that is less than required to operate the overcurrent protection device of the supply circuit.


Guarding - The covering or barrier that separates you from live electrical parts.


Hazard - A source of possible injury or damage to health.


Hazard Risk Category (HRC) - A NFPA 70E 2012 rating system used to determine the AR of PPE for a specific task. There are four categories listed from HRC 1 to HRC 4. Note: NFPA 70E 2015 has replaced HRC with "arc rated PPE category" and eliminated the HRC 0 level.


Insulator - Any material with a high level of resistance that prevents the flow of electrons such as rubber, plastic, glass, etc., the opposite of a conductor. Note: Air space can be considered a type of insulation.


Insulated Tools - Tools or equipment designed to provide insulation from an energized part or conductor. It may have conductive parts and be coated or covered by a dielectric material, or it may be composed entirely of insulating materials. Insulated industrial hand tools are typically stamped on the handle with an emblem (a double triangle) and a voltage rating. Such tools must be ASTM certified.


Insulating Protective Equipment (IPE) - Such as line hoses, rubber hoods, rubber blankets, and insulating live-line tools (for example, hotsticks, switchsticks, or shotgun sticks) for protection. However, since IPE is not worn, it is technically not considered to be PPE.


Overcurrent - Any current that exceeds the safety rated current of equipment or the ampacity of a conductor. It may result from overload, short circuit or ground fault.


Overcurrent Protection Device (OCPD) - A device that shuts off the current in a circuit when it reaches a certain level.


Overload - A current load greater than the load for which the system or mechanism was intended. A fault, such as a short circuit or ground fault, is not an overload.


Panel Board - (also panelboard or distribution board) A cabinet with an access door(s) which contains electrical devices such as, circuit breakers uses, short-circuit protection devices, usually mounted in or on a wall or on the device it is associated with.


Personal Protective Equipment (PPE) - Clothing or other devices usually worn to protect the user from harm in the workplace. In the case of electrical hazards, protecting the user from the effects of arc flash /blast hazards.


Qualified Person - NFPA 70E 2015, a national standard, addresses the standards for electrical safety in the workplace. It defines a "Qualified Person" as: "One who has demonstrated skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to identify and avoid the hazards involved." 


Rated Voltage - The maximum voltage at which an electric component can operate for extended periods without undue degradation or safety hazard.


Risk - A combination of the likelihood of occurrence of injury or damage to health and the severity of injury or damage to health that results from a hazard. (NFPA 70E 2015)


Risk Assessment - An overall process that identifies hazards, estimates the potential severity of injury or damage to health, estimates the likelihood of occurrence of injury or damage to health, and determines if protective measures are required. Informational Note: As used in this standard, arc flash risk assessment and shock risk assessment are types of risk assessments. (NFPA 70E 2015)

Also: A combination of the likelihood of occurrence of injury or damage to health and the severity of injury or damage to health that results from a hazard.


Short Circuit - Also referred to as a "short", it is a connection that allows current to flow through a low-resistance, unintended path between two points in an electrical circuit.


Switchboard - A large single panel, frame, or assembly of panels having switches, overcurrent, and other protective devices, buses, and usually instruments mounted on the face or back or both. Switchboards are generally accessible from the rear and from the front and are not intended to be installed in cabinets.


Switchgear - Electrical supply disconnect equipment consisting of switches and circuit protection devices combined with control, metering and regulating devices in a power system. It is used to isolate and de-energize electrical equipment downstream for accessibility and to clear faults.


V-rated - Line-to line voltage at location of where work is to be performed tested and rated for equipment such as gloves, tools used for near or direct contact of electrical equipment. Must meet ASTM certifications.


Figure 1: Arc Flash/Blast



Figure 2: Balaclava Nomex Fire Resistant Head Covering



Figure 3: Current Limiting Fuses in AIMSS



Figure 4: Energy Control/Power Lockout (LOTO)


Figure 5: Electrical Guarding



Figure 6: Insulated Tool



Figure 7: Electrical Cabinet Panel Board



Figure 8: Rated Voltage



Figure 9: Switchboards



Figure 10: Switchgear

Quiz Group

Test your knowledge by answering the following questions.

 Question 1

 Question 2

 Question 3

 Question 4

 Question 5



Electrical Safety Overview

Some Electrical Basics

Basic Ohm's Law:


Ohm's Law for Electric current (amps), voltage and resistance states:


One volt is required to push one amp through one ohm.

E = Voltage = V (volts)

I = Current = A (amperage)

R = Resistance = (ohms)


Figure 1: Ohm's Law Pie Chart


Electricity and the Human Body

 Why 50 volts?

  • The typical body has a contact resistance of 500 ohms at the point of contact with the electrical source.
  • The body has an internal resistance of approximately 100 ohms.
  • Touch/Step potential to ground of about 5000 ohms (Ω is the symbol for ohms).
  • Combine the resistances to find the total resistance

  500Ω + 100Ω + 5000Ω = 5600 Ω

To find the amount of current the body is subjected to when in contact with 120V electrical source:

  • 50v / 5600 Ω = 8.9 mA
  • 120v / 5600 Ω = 21 mA
  • It is around 10 mA that the "cannot let go" level is reached. Once muscle lock-up occurs, exposure time is amplified and the probability of electrocution increases dramatically.


Figure 1: The Human Body is Conductive


Figure 2: Effects of Electric Shock on the Body

Resistance and the Human Body

  • The body has a natural defense system (skin). Dry skin resistance can be 100,000 ohms or more depending on several factors including skin thickness, dryness levels, calluses.
    • Do whatever you can to raise your body's resistance.
    • The key to survival is to decrease exposure.
    • The typical body has a contact resistance of 500 ohms at the point of contact with the electrical source.
    • The body has an internal resistance as low as 100 ohms.
  • Water and perspiration (sweat and sodium chloride spell danger) can make a human body more conductive.
    • Wet floors make this condition worse.
    • Wet floors present slip, trip and fall hazards, as well.
    • Good housekeeping has many benefits.
  • Contact points with energized sources and the human body should be avoided.
    • Electric current starts to break down the resistance of skin, increasing current exposure.
    • Wearing jewelry and/or watches may increase the amount of current one's body is exposed to.
    • Rings, watches and other jewelry might "catch" and cause injury.
    • Some electricians place a hand in their pocket to help prevent current from traveling through the chest and heart.


Figure 1: Wet Floor Sign



Figure 2: Electrician with One Hand in Pocket

Touch/Step Potential

Electricity will typically travel through the body one of three pathways:

Touch Potential (Hand-to-Hand)

  • Potential to ground of about 1000Ω (ohms).
  • Current passing across the chest, through the heart and lungs causes the most serious internal injuries.
  • Heart fibrillation (abnormal heartbeat known as arrhythmia).
  • Atrial fibrillation (AFib)- upper heart chambers (serious).
  • Ventricular fibrillation (VFib) )- lower heart chambers (more serious - typical cause of death in electrocutions).
  • Difficulty breathing or respiratory system paralysis.
  • Lapse into unconsciousness (with potential injuries from falling).

Step Potential (Foot-to-Foot)

  • Does not cross the chest and heart is not in direct path.
  • May paralyze the victim temporally.
  • Possibility of collapse (with potential for injuries from falling).

Touch/Step (Hand-to-Hand or Foot-to-Hand)

  • Potential to ground of about 5000Ω (ohms).
  • Current passing across the chest, through the heart and lungs causes the most serious internal injuries.
  • Heart fibrillation (abnormal heartbeat known as arrhythmia).
  • Atrial fibrillation (AFib)- upper heart chambers (serious).
  • Ventricular fibrillation (VFib) )- lower heart chambers (more serious - typical cause of death in electrocutions).
  • Difficulty breathing or respiratory system paralysis.
  • Lapse into unconsciousness (with potential injuries from falling).



Figure 1: Touch/Step Potential and the Human Body


Arc Flash Injuries

Types of Injuries

Tissue/muscle/skeletal at points of contact - either from direct contact with electrical arc with entry and exit from source to ground, or typically burns from the arc flash/blast.


  • Internal organ damage either from electrical contact or blunt force trauma from arc blast.


  • Death - immediate electrocution, blunt force trauma or sustained injuries.


  • Secondary injuries (fall, muscle spasms, etc.)

Severity of Injuries

There are three factors that determine how severe an arc flash injury will be:

  1. How close the person is to the arc flash/blast hazard.
  2. The temperature of the event.
  3. The length of time exposed to the event (before the circuit is disconnected).

The severity of injuries due to the electrical contact depends on the following factors:

  • Amount of current:
    • Type of current AC or DC (DC current requires more milliamps to cause the same damage as AC current 30 mA for AC vs 300-500 mA for DC to cause heart fibrillation).
    • NOTE that both can still be lethal.
  • The pathway the current took through the body.
  • Duration of contact (before the circuit is disconnected):
    • Lower voltages for longer periods of time can also cause injury or death.
    • The heat energy delivered to tissues is proportional to the square of the voltage (increasing the voltage by a factor of 10 increases the heat energy by a factor of 100).

Arc Flash Injury Example

  • A man was near a power box when an electrical explosion occurred.
  • Although he did not touch the electrical enclosure, an electrical discharge, in the form of an arc, traveled through the air, and entered his body.
  • The current was drawn to his armpits because perspiration is very conductive.

The deadly force that occurs upon contact with energized sources is:

The flow of electrons through the body!

Make no mistake:

CURRENT (the flow of electrons) KILLS and It only takes a very small amount.

Electrocution can occur with only the amount of electricity needed to light a 7 ½ W, 120v lamp if it passes across the chest and through the heart either from hand-to-hand or hand-to-foot pathways.




Figure 1: Electrical Burns


Skin Temperature

Exposure Time

Damage Result

110° F

6 Hours

Cell Breakdown begins

158° F

1 second

Total cell destruction

176° F

0.1 second

Curable burn

200° F

0.1 second

Incurable burn

Figure 2: Skin Temperature and Damage Threshold



Figure 3: Worker Armpit Injury

Myths and Misconceptions

Arc Flash events rarely happen.

A widely quoted estimate from Chicago-based research firm CapSchell, Inc., is that there are an average of 5 to 10 reported arc flashes every day, that is over 3,000 per year.


NFPA and IEEE 1992 through 2002 recorded over 2000/year arc flash injuries, 5 victims/day.

  • Each year, more than 2,000 people are admitted to burn centers with severe arc flash burns.
  • Also noted: 80% of fatalities in electrical worker are due to burn injuries, not electrical shock.

There were 961 fatal injuries due to exposure to electrical current, radiation, temperature and pressure in the period of 2008 through 2012 as reported from the National Safety Council in their 2014 publication of Injury Facts.

If I wear FR apparel and wear a face shield I'm protected and compliant.

Arc flash /blast envelops the victim, make sure you wear the proper level PPE for the task and hazard analysis.

Work permits may be required as well for energized work on equipment over 50 volts.

I've been an electrician for many years and I've never seen an arc flash.

Studies indicate that years of experience does not necessary equate to increased safety when it comes to arc flash.

  • Bureau of Labor Statistics (1-1-2011) indicates the average arc flash victim has 11.5 years of experience.
  • Study by the NFPA and BLS showed that the average age groups are almost equally divided, the difference being the voltage levels of equipment serviced.



Figure 1: Arc Flash Fall Injury

Common Practices

Important Safety Recommendations: NFPA 70E

NFPA 70E Article 120 Establish an "electrically safe work condition" before working on a circuit by deenergizing it.

Create an "electrically safe work condition" by… *

(1) Identifying all power sources,

(2) Interrupting the load and disconnecting power,

(3) Visually verifying that a disconnect has opened the circuit,

(4) Locking out and tagging the circuit,

(5) Testing for voltage, and

(6) Grounding all power conductors. (used for stored or induced electrical energy and bare-hand work)

*All of these steps require the use of appropriate personnel protective equipment for shock and arc flash protection: safety glasses, voltage rated gloves, fire–resistant (FR) work clothes, arc–rated face shields, flash suits with hoods, and hearing protection.


Energy Control and Power Lockout ECPL

Whenever a worker has to be placed in a position where a part of their body may be exposed to unexpected movement, release of stored energy, electrical system energizing or potential of exposure to the flow of liquids or gasses, they have the authorization and responsibility to effectively de-energize the machinery or equipment to prevent injury or death.

Before working on any machine or equipment, it is imperative that while it is being serviced to first remove its source of electrical power. The removal of all energy sources by disconnecting and making equipment safe (inoperable) is known as energy isolation. The procedure for shutting off the power and preventing it from being energized while the work is being done is called Lockout/Tagout. This de-energized state is also referred to as creating an electrically safe work condition, abbreviated as "ESWC".


Locking out and tagging equipment does not guarantee the electrical hazards have been eliminated until the equipment is verified as being in an de-energized state. Workers must continue to perform energized electrical equipment safety practices and wear PPE appropriate for the level of incident energy until the "ESWC" is established.


OSHA 1910.147(b) defines an energy source as "Any source of electrical, mechanical, hydraulic, pneumatic, chemical, thermal, or other energy."


It is important that you know each of the OSHA recommended 8 steps for lockout/tagout in proper sequence and that you know that each person who works on equipment should have his or her own lock for preventing a piece of equipment from being started inadvertently. See OSHA's 1910.147(c)(4) Energy control procedure and 1910.147 App A . Typical minimal lockout procedures.


Click on the link below to read OSHA requirements for lockout/tagout:

OSHA FACT Sheet Lockout/Tagout

Clicking the link will open a new browser window. Close the new window to return to this lesson.


NOTE: Every facility or plant will have its own machine and equipment lockout/tagout standards and which must be followed at all times.



Figure 1: Energy Control Power Lockout

OSHA 1910 Sequence of Lockout


(1) Notify all affected employees that servicing or maintenance is required on a machine or equipment and that the machine or equipment must be shut down and locked out to perform the servicing or maintenance.


(2) The authorized employee shall refer to the company procedure to identify the type and magnitude of the energy that the machine or equipment utilizes, shall understand the hazards of the energy, and shall know the methods to control the energy.


(3) If the machine or equipment is operating, shut it down by the normal stopping procedure (depress the stop button, open switch, close valve, etc.).


(4) De-activate the energy isolating device(s) so that the machine or equipment is isolated from the energy source(s).


(5) Lock out the energy isolating device(s) with assigned individual lock(s).


(6) Stored or residual energy (such as that in capacitors, springs, elevated machine members, rotating flywheels, hydraulic systems, and air, gas, steam, or water pressure, etc.) must be dissipated or restrained by methods such as grounding, repositioning, blocking, bleeding down, etc.


(7) Ensure that the equipment is disconnected from the energy source(s) by first checking that no personnel are exposed, then verify the isolation of the equipment by operating the push button or other normal operating control(s) or by testing to make certain the equipment will not operate.

Caution: Return operating control(s) to neutral or "off" position after verifying the isolation of the equipment.


(8) The machine or equipment is now locked out.


Restoring Equipment to Service

When the servicing or maintenance is completed and the machine or equipment is ready to return to normal operating condition, the following steps shall be taken.


(1) Check the machine or equipment and the immediate area around the machine to ensure that nonessential items have been removed and that the machine or equipment components are operationally intact.


(2) Check the work area to ensure that all employees have been safely positioned or removed from the area.


(3) Verify that the controls are in neutral.


(4) Remove the lockout devices and reenergize the machine or equipment.


Note: The removal of some forms of blocking may require reenergization of of the machine before safe removal.


(5) Notify affected employees that the servicing or maintenance is completed and the machine or equipment is ready for use.

Figure 2: OSHA 8-Step Sequence of Lockout and
5-Step Restoring Equipment to Service Procedures

Energized Electrical Work Permit (EEWP)

The NFPA and OSHA regulations stipulate that service and maintenance work should be done on de-energized equipment.

"Hot" work, that is working on equipment in an energized state is allowed by both OSHA and NFPA under strict guidelines.

Use a written permit system for planning and conducting work on or near energized parts. A permit contains the following information:

  • Why and how the work will be conducted.
  • Detailed information about the shock and flash hazards involved:
    • EHA required on all circuits 50V or higher
  • Safe work practices to be used.
  • Personal protective equipment (PPE) to be used.
  • Authorization for the energized work (signatures).
  • The approach boundaries defined.
  • Circuit and equipment description/ location.
  • Preliminary job briefing record.
  • Worker training and certification documented.
  • Arc flash risk assessments.
  • Access restrictions (barriers) to be used.

Click on the link below to view a sample Energized Electrical Work Permit:

Energized Electrical Work Permit

Clicking the link will open a new browser window. Close the new window to return to this lesson.

Energized Work Is Permitted When

  1. When the employer demonstrates that it is not possible to power down because of an increased hazard.
  2. Is deemed infeasible by the employer due to the design of equipment or limitations in operation.
  3. Working on equipment less than 50 volts.
  4. Under normal operation (the risk associated is acceptable) when the equipment:
    • has been properly installed to industry codes and standards.
    • has been maintained properly to manufacturer's. recommendations and industry standards and codes.
    • has all doors are closed and secured.
    • has all covers in place and secured.
    • has no evidence of "impending" failure such as arcing, overheating, loose damaged or deteriorating parts.

Exemptions to Needing a EEWP When Performing Energized Work

Work performed within the limited approach boundary of energized electrical conductors or circuit parts by qualified persons (or an un-qualified person under continual escort by a qualified person), utilizing safe work practices and proper PPE, related to the following tasks:

  • Testing, troubleshooting voltage/current measurements
  • Thermography and visual inspection techniques are used
  • General housekeeping duties (non-electrical tasks) outside the restricted approach boundary
  • Accessing an area outside the restricted approach boundary if no electrical work is done


Figure 1: Workers Discussing Work Permit

NFPA 70E 2015 Article 130.2(B)(1) Energized Electrical Work Permits.

When Required: When energized work is permitted in accordance with 130.2(A), and energized electrical work permit shall be required under the following conditions:

(1) When work is performed within the restricted approach boundary

(2) When the employee interacts with the equipment when conductors or circuit parts are not exposed but an increased likelihood of injury from an exposure to an arc flash hazard exists.


OHSA CFR 1910.333(c)(2) states that:

"Only qualified persons may work on electric circuit parts or equipment that have not been de-energized…Such persons shall be capable of working safely on energized circuits and shall be familiar with the proper use of special precautionary techniques, personal protective equipment, insulating and shielding materials, and insulated tools."

Figure 2: Applicable Standards

Worker Seriously Burned in Arc Flash Explosion

Workers were installing 480-volt nominal service at a food processing plant for future use. At the time, the plant was using existing service at the same branch circuits. The system was live at the panel where the workers were attempting to take a measurement for an additional service wire.

The victim was waiting at the end of eight separate conduit holes to retrieve fish tape that workers on the second floor were running through conduit they had installed for the new service.

Although he was not sure from which one of the eight conduits the fish tape would emerge, he lay on the ground expecting it to be a lower one. As he was watching, the end of the tape sprung out of a higher conduit; however, because the bus bar was activated and carrying an electrical load of approximately 480 volts nominal AC and 3,000 amps, as soon as it touched the back of the bus bar, it created an explosion and fireball.

He received burns from the fireball on his face and the back of his hands. The arc flash blew out two of the branch circuit boxes and burned the rest of the services.

One of the other workers, who was watching as the victim was attempting to receive the fish tape, immediately ran down two flights of stairs to tend to him after the accident.

Another employee, who was pushing the fish tape through from the second floor, experienced a near miss when a flame came out of the conduit just two feet from his shoulder. He felt the heat of the 1,500-degree flame but did not receive an injury.

After emergency responders arrived, the victim was transported to a nearby hospital where he was treated and transferred to the Oregon Burn Unit in Portland for second- and third-degree burns to his face and hands.

The work required a Level II hot work permit, which included a qualified buddy (journeyman electrician), hard hats, safety glasses, full-face shield (flash rated, nonconductive), rubber gloves (properly rated and tested at 1,000 volts per minute), double-insulated hand tools, flame retardant outer garments, a copy of the "hot work process," and a rescue system.


Figure 1: Workers with Proper PPE

Courtesy of Dean Thomas, GTRI

Applicable Standards

1926.416 (a)(1) Safety related work practices, general requirements – "No employer shall permit an employee to work in such proximity to any part of an electric power circuit so that the employee could contact the electric power circuit in the course of work, unless the employee is protected against electric shock by de-energizing the circuit and grounding it or by guarding it effectively by insulation or other means."


437-001-0760 (1)(a) Rules for all workplaces, employers' responsibilities – "The employer must see that workers are properly supervised in the safe operation of any machinery, tools, equipment, process, or practice that they are authorized to use or apply."


437-001-0760 (1)(b)(C) Rules for all workplaces, employers' responsibilities – "The employer shall take all reasonable means to require employees to use all means and methods, including, but not limited to, ladders, scaffolds, guardrails, machine guards, safety belt, and lifelines, that are necessary to safely accomplish all work where employees are exposed to a hazard."

Figure 2: Applicable Standards


Use tools, meters, and other equipment that are suitable for the voltage and current levels present when performing all electrical work. If dropped or slipped while working on live equipment, they may reduce the possibility of creating an arc flash incident. In addition, using proper torque control limits the use of excessive force being applied which could lead to the tool slipping off.

Insulated tools or equipment are designed to provide insulation from an energized part or conductor. They may have conductive parts and be adequately coated or covered by a dielectric material, or may be composed entirely of insulating materials. Insulated industrial hand tools are typically V-rated (voltage rated) stamped on the handle with an emblem of a double triangle. Such tools must be certified that meet ASTM F1505 Specification for Insulated Hand Tools and OSHA 29 CFR 1910.335(a)(2)(i) standards.

NFPA 70E 2015 130.7(D)(1) Insulated Tools and Equipment states that employees must use insulated tools when working inside the limited approach boundary. The NFPA 130.7(C)(15)(a) Hazard/Risk Category Classifications table list tasks that require insulated hand tools.

When working on energized equipment:

  • Hand tools must be rated at least 1000 VAC/1500 VDC and are tested to 10,000 VAC for a ten-fold margin of safety.
  • Use tools that are insulated to at least the level of the voltage levels that they will be exposed.
  • The manufacturer, year of manufacture, part or code number must be identified on tool.
  • All tools must be inspected/tested for damage prior to each use.
  • If tools are found to be damaged, immediately remove from service.

NOTE: Wrapping a tool in electrical tape or non-conductive material does not qualify it as an insulated tool.

Testing Meters

Electrical testing devices such as voltage meter, ohmmeter, etc., can be the cause of an arc flash incident:

  • Defective equipment:
    • probe leads that may detach and make contact with live conductors
    • failure of internal components and safety features
    • faulty readings giving false information regarding status of equipment
  • Human error:
    • probe tip slips off connection point and makes contact with live conduit
    • hand slips off probe and makes contact with live conductor
    • probe leads in wrong jacks
    • meter set incorrectly for input voltage rated on equipment
    • readings interpreted incorrectly giving false information regarding status of equipment
    • using testing equipment not sufficiently rated for the equipment being tested

Testing meters should be carefully selected on their intended use, safety features, and voltage ratings and used strictly according to the manufacturer's instructions.


NFPA 2015 Article 250.4 Test Instruments and 110.4 Use of Electrical Equipment requires that test instruments and the leads used for the purpose of detection of voltage need to be functionally maintained and verified.


Figure 1: Voltage Rated Tools



Figure 2: Using V-Rated Tool on De-energized Equipment



Figure 3: Voltage Tester

Training Requirements Emergency Response Training Contact Release

A worker who is in contact with an electrical source may not be conscious or may be experiencing "muscle clamping" where the releasing of the conductor is impossible because of the involuntary contraction of muscles due to current flow. A rescuer attempting to pull the victim from the source of electricity may themselves become energized and become a victim. When approaching a victim, caution should be the primary consideration as well as performing an effective and speedy rescue. Safely de-energize the electrical equipment if possible at the disconnect switch, circuit breaker, emergency shut-off device, removing the power source, etc. Contact emergency response personnel as soon as possible.

Considerations if the power source cannot be disconnected:

  • Determine if victim is in contact with energized source directly or through contact with an electrical conductive source as in water.
  • Look for other potential hazards sources such as stored energy, fire, heated surfaces.
  • Ensure rescuers' hands and feet are dry and insulated if available.
  • Pick a position to stand that is clean and dry or use a energy isolating (rubber) blanket or other non-conducting material.
  • Use a object such as a rescue or "hot" stick, dry stick or length of wood, plastic or rope made of non-conductive material to move the victim or detach the electrical source.

Start CPR and first aid as soon as it can be safely performed. Every minute counts to increase the victim's chance of survival.


The NFPA 70E Article 110.2(C)(1) Training Requirements Emergency Response Training Contact Release. Requires emergency response training for employees who work with energized electrical equipment and are exposed to shock hazards with annual refresher training.


OSHA and the NFPA (Article 110.2(C)(2) Resuscitation) require that the employers regularly train (verified annually) the employees who are responsible for responding to medical emergencies in the absence of medical personnel, which includes first aid, procedures, approved methods of resuscitation, cardiopulmonary resuscitation (CPR) as well as the use of automated external defibrillator (AED).


Though not mandatory for non-medical emergency response personnel, all employees should be trained in the basic first aid, cardiopulmonary resuscitation CPR and automated external defibrillator (AED) use.


Formal CPR and AED training is typically provided by the employer though outside training organizations such as the American Red Cross.


Figure 1: Emergency Response Contact Release



Employer Obligation

The organization has a responsibility in preventing arc flash injuries. It has the ability to provide a safety analysis of the workplace and develop engineering controls to eliminate hazards. It can engineer new or retrofitted facilities, incorporating the latest safety technology. Organizations have the duty to provide appropriate tools, PPE, and regular maintenance of equipment and training (every three years). A commitment to training is a commitment to safety. Partnerships with equipment suppliers can bring innovative and safer technology to the workplace. Most importantly, management can demonstrate the value of safety to their employees, customers, and other stakeholders through their actions, which creates a positive safety climate where people watch out for each other.


Section 5(a)(1) of the OSH Act states: "Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees", often referred to as "The General Duty Clause".


Employers have the responsibility to:

  • provide a workplace free from recognized hazards and comply with OSHA standards
  • provide employee training required by OSHA standards.
  • keep records of injuries and illnesses.
  • provide medical exams and access to exposure and medical records
  • not discriminate against workers who exercise their rights (under the Act (Section 11(c)).
  • post OSHA citations and abatement verification notices.
  • provide and pay for PPE.


As an employee, you have the right to:

  • a safe and healthful workplace
  • know about hazardous chemicals
  • information about injuries and illnesses in your workplace
  • complain or request hazard correction from your employer
  • training
  • hazardous exposure records and medical records
  • file a complaint with OSHA
  • participate in an OSHA inspection
  • be free from retaliation for exercising safety and health rights
  • worker responsibilities



Figure 1: OSHA Job Safety and Workers Rights Poster

Clicking the link will open a new browser window. Close the new window to return to this lesson.

Shock Risk Assessment Overview

OSHA 1910.132 (d) and 1926.28(a) states that the employer is responsible to assess the hazards in the work place, and to select, have and use correct PPE and document the assessment.

Is a requirement to issue Energized Work Permits and justify performing work on energized electrical equipment.

Shock Risk Assessment is determined by qualified personnel using guidelines, calculations and the tables required for the application. It is not expected that an employee not specifically trained to calculate arc flash incident values be required to do so, however it is expected that they can read and understand the information provided on an arc flash label.

How is the PPE required determined?

First, there must be an Arc Flash Risk Assessment to determine if an arc flash hazard exists and if there is, the following are determined:

  • appropriate safety related work practices associated with the equipment
  • the arc flash boundary for the area affected
  • and the PPE requires to be used within this boundary

There are many methods, software programs and companies providing this service, the two that are widely used are:

IEEE 1584 Arc-Flash Hazard Calculation, "Guide for Performing Arc-Flash Hazard Calculations." which contains detailed methods, steps and data that can be used to calculate Arc-Flash Hazards for electrical systems.


NFPA 70E Article 130 Annex D, Incident Energy and Arc Flash Boundary Calculation Methods contains information on several methods used to calculate incident energy and arc flash boundaries.


There is a third method used if the criteria in the standards are met:

NFPA 70E 2015 Table 130.7(C)(15)(a) for AC systems and NFPA 70E 2015 Table 130.7(C)(15)(b) for DC Hazard/Risk Categories, Table Method - an alternative method which uses tables with various tasks to be performed on energized electrical equipment to assess Hazard Risk Categories and the proper PPE required. This is not a replacement for a complete Flash Hazard Analysis and may only be used in some applications. It is subject to specific provisions as specified in the articles.


A significant revision in the NFPA 70E 2015 update states that the arc flash boundary distance is to be calculated for all locations where the voltage is 50 volts or more and there is a possibility of a worker performing energized work such as maintenance, diagnostics and testing being exposed to an arc-flash risk.


NFPA 70E Article 100. Definitions.

Risk. A combination of the likelihood of occurrence of injury or damage to health and the severity of injury or damage to health, that results from a hazard.

Risk Assessment. An overall process that identifies hazards, estimates the potential severity of injury or damage to health, estimates the likelihood of occurrence of injury or damage to health, and determines if protective measures are required.

  • Informational Note: As used in this Standard, "arc flash risk assessment" and "shock risk assessment" are types of risk assessments.



Figure 1: Electrical Panelboard and Transformer Requiring Arc Flash Labeling

Courtesy of Dean Thomas, GTRI


NFPA 70E 2015 Article 130.5 Arc Flash Risk Assessment.

An arc flash risk assessment shall be performed and shall:

(1) Determine if an arc flash hazard exists. If an arc flash hazard exists, the risk assessment shall determine: a. Appropriate safety-related work practices b. The arc flash boundary c. The PPE to be used within the arc flash boundary

(2) Updated with major modifications and reviewed periodically, at intervals not to exceed 5 yrs.

(3) Take into consideration the design of the overcorrect protective device and its opening time, including its condition of maintenance.

Informational Note No. 1: Where equipment is not properly installed or maintained, PPE selection based upon incident energy analysis or the PPE category method may not provide adequate protection from arc flash hazards.

Figure 2: NFPA 70E 2015 Article 130.5 Arc Flash Risk Assessment




Employee Obligation

Employees must follow the requirements of the Arc Flash Hazard Label by wearing the proper personal protective equipment (PPE), use of insulated tools and other safety related precautions. This includes not working on or near the circuit unless you are a "qualified" worker.

Each employee should be responsible for his or her own electrical safety self-discipline.


OSH ACT - Occupational Safety and Health Act of 1970

Although OSHA does not cite employees for violations of their responsibilities, each employee "shall comply with all occupational safety and health standards and all rules, regulations, and orders issued under the Act" that are applicable. Employee responsibilities and rights in states with their own occupational safety and health programs are generally the same as for workers in states covered by Federal OSHA.

An employee should do the following:

  • Read the OSHA poster at the jobsite.
  • Comply with all applicable OSHA standards.
  • Follow all lawful employer safety and health rules and regulations, and wear or use prescribed protective equipment while working.
  • Report hazardous conditions to the supervisor.
  • Report any job-related injury or illness to the employer, and seek treatment promptly.
  • Cooperate with the OSHA compliance officer conducting an inspection if he or she inquires about safety and health conditions in the workplace.
  • Exercise your rights under the act in a responsible manner.



Figure 1: OSH Act of 1970 Sec 5 Duties (b)

Arc Flash Boundaries - 2012

Arc flash labels produced up to the NFPA 70E 2012 arc flash standards had defined four boundaries: three are shock protection boundaries and an outer flash protection boundary based on calculations of the voltage of the electrical equipment affected. You may encounter these in the field so they will be covered briefly.

NFPA 70E 2015 arc flash boundaries has only two shock protection boundaries as it has eliminated the "Prohibited Approach" Boundary.

For 2012 labels (superseded by NFPA 70E 2015)

Flash Protection Boundary - This is the outermost boundary, furthest away from the energy source of the potential arc flash hazard an unqualified person can approach unaccompanied. An unqualified person may only cross this boundary accompanied by a qualified worker. Should an arc flash occur, the person exposed to the blast would be subjected to the heat generated by the flash resulting in second degree burns (1.2 calories/cm2) which is typically curable. At this distance PPE must be worn to prevent 2nd degree (or greater) burns if exposed to the arc flash.

Limited Approach Boundary - Only qualified persons within this boundary. This is the distance an unqualified person may enter when continuously accompanied by a qualified worker, wear the appropriate level of PPE and trained for the task.

Restricted Approach Boundary - Shock Protection and Flash Protection. This boundary is restricted to unqualified personnel. Only a qualified worker, wearing the appropriate level of PPE and properly trained for the task to be performed may enter this area. It also requires an approved work permit with a written plan of the task to be performed. The written plan should include well defined procedures to prevent exposure to shock hazards in the Prohibitive Approach Boundary defined below.

Prohibited Approach Boundary (the center most region removed in NFPA 70E 2015) - Treat as if in contact with live parts. Energized, exposed conductors or parts. This area exposes unprotected, conductive body parts and tools to direct electrical contact or arc. Only qualified workers can cross this boundary wearing the appropriate level of PPE rated for direct contact with live electrical equipment. A risk assessment must have been performed prior to entering.


Figure 1: Arc Flash Boundaries 2012

Arc Flash Boundaries - 2015

Arc flash labels produced to the NFPA 70E 2015 arc flash standards have three defined boundaries: two are shock protection boundaries and the outer flash protection boundary based on calculations of the incident energy calculations and maintenance of the electrical equipment affected.

Flash Protection Boundary - This is the outermost boundary, furthest away from the energy source of the potential arc flash hazard an unqualified person can approach unaccompanied. An unqualified person may only cross this boundary accompanied by a qualified worker. Should an arc flash occur, the person exposed to the blast would be subjected to the heat generated by the flash resulting in second degree burns (1.2 calories/cm2) which is typically curable. At this distance PPE must be worn to prevent 2nd degree (or greater) burns if exposed to the arc flash.

Limited Approach Boundary - Only qualified persons within this boundary. This is the distance an unqualified person may enter when continuously accompanied by a qualified worker, wear the appropriate level of PPE and trained for the task.

Restricted Approach Boundary - Shock Protection and Flash Protection. This boundary is restricted to unqualified personnel. Only a qualified worker, wearing the appropriate level of PPE and properly trained for the task to be performed may enter this area. It also requires an approved work permit with a written plan of the task to be performed. The written plan should include well defined procedures to prevent exposure to shock hazards in the Restrictive Approach Boundary.

As stated in NFPA 70E 2015 Article 130.4(D) Restricted Approach Boundary:

This applies to working on systems that have exposed energized electrical conductors or circuit parts that are operating at 50 volts or more.

  • Only a qualified person may enter, with or without a conductive object, closer to exposed energized electrical conductors or circuit parts unless one of the following conditions applies:
    • The qualified person is wearing or using PPE and/or insulated appropriately (using insulating materials such as rubber blankets for instance) from the conductor for the task to be performed.
    • If an uninsulated part of the body is required to contact exposed energized parts or circuits a combination of the next two provisions apply (this type of work requires special training):
  • The energized conductors or part are insulated from making contact with the uninsulated body parts or other conductive object (of a different potential).
  • The exposed part of the qualified person is insulated (appropriately rated PPE and/or insulated from another conductive object or ground).

Complete the Quiz Me activity below.


Figure 1: Arc Flash Boundaries 2015

 Toggle open/close quiz question

Reading Warning Labels

NFPA 70E 2015 Article 130.5 (D). Equipment Labeling requires that electrical equipment that are in locations other than dwelling places (residential housing), such as:

  • Electrical switchboards
  • Electrical panels
  • Panelboards
  • Electrical control panels
  • Meter socket enclosures
  • Motor controls centers

and are likely to be serviced by a worker when in an energized sate, must be field marked with a warning label including all the following information:

  1. The nominal system voltage.
  2. The arc flash boundary.
  3. At least one of the following:
  • Available incident energy and the corresponding working distance (Calorie Rating @ 18″).
  • Minimum arc rating of clothing (PPE).
  • Required level of PPE to use.

Article 130.5(D) also states that it is the electrical equipment owner's responsibility for the field-marked label documentation, installation, and maintenance.


There are many versions of the Arc Flash Label which dispense different information depending on the standard's time period it was issued. The following are examples of arc flash labels that may be encountered in the field:


Labels headers are specified to be based on ANSI Z535.4 - Product Safety Signs and Labels.


Signal Words

Caution (black letters on yellow background): ANSI Z535 standard uses "Caution" labels for hazards that could result in minor or moderate personal injury, but not death. Since arc flashes usually involve enough power to cause serious injury, the Caution labels are not typically used for arc flash.


Warning (black letters on orange background): labels and signs, under the ANSI Z535 standard, should be used when a hazard could result in death or serious injury. Some facilities use "Warning" when they have the required PPE for energized equipment work.


Danger (white letters on red background): should be used for the most severe hazards, which would probably result in death or serious injury. May be used when the equipment must be powered down instead of doing energized work. Some facilities use an incident energy of 40 cal/cm² as the cut-off, with more powerful flashes being marked with "Danger."


And may include an arc flash symbol or graphic (pictogram) though not specifically required.


Minimal Generic Label

A basic label with no details that would that meet OSHA's and the NEC's basic requirements to inform a worker about a hazard, but it does not meet the NFPA's standard for providing useful arc flash information.


2012 Label

Notice that this is the same as the 2015 release but the fourth provision under the NFPA 70E 2012 Article 130.5 (C) 1, "Highest Hazard Risk Category (HRC) to use" has been removed. This is now replaced with the results from either an incident energy analysis or the Arc Flash PPE Category method but not both.

All references to the Prohibited Approach Boundary are deleted in the 2015 edition. The flash protection, limited approach and restricted approach boundaries are defined.

Hazard/Risk Category Classifications (eliminated in NFPA 70E 2015)

Prior to the 2015 update to the NFPA 70E this was the standard method to determine the level of PPE required and is used by some manufacturers to identify the arc-flash rating of their garments and equipment though not required—they are required that the cal/cm2 garment rating be shown. However, it is still very common to see on labels, tags, specifications, and other information provided.


Figure 1: Arc Flash Label on Electrical Disconnect Switch


Figure 2: Arc Flash Label 2015 NFPA 70E Requirements



Figure 3: Minimal Generic Arc Flash Labels


Figure 4: Arc Flash Label 2012 NFPA 70E Requirements

AMTEC Integrated Manufacturing System Simulator (AIMSS) Example

It is important to understand the equipment that is being serviced. Using electrical drawings and knowledge of system components is critical to identifying possible arc flash hazard points. The power coming into the electrically energized equipment may come from the plant or directly from the utility power distribution system. Where the utility system and the equipment connect is referred to as the service point. The electrical system which enters the disconnect is "upstream", known as the line side. The power exiting the service point after the disconnect is considered the load side, "downstream" of this point, and is where applicable NFPA and NEC regulations are to be followed by the equipment owner. Power may be still live inside cabinet when locked out at the line side of the disconnect unless power was disabled further upstream. Note that an employee working on the utility side of the service point is required by OSHA to follow its General Industry safety standards which recognizes the NFPA 70E standards.

Many components within an electrical cabinet or panel may have one level of line voltage coming into it and another level exiting, with the line side incident energy being normally higher than the load side incident energy. Use the AMTEC Integrated Manufacturing Systems Simulator (AIMSS) (Figure 1) as an example to identify potential sources of arc flash components in the electrical cabinet.


Figure 1: AIMSS Electrical Panel

Clicking the image will open a new browser window. Close the new window to return to this lesson.

Personal Protection Equipment

Who must wear Personal Protection Equipment (PPE)?

Appropriate PPE must be worn by all personnel performing any work or checks on live exposed conductors.


OSHA 1910.335(a)(1)(i)

Employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment that is appropriate for the specific parts of the body to be protected and for the work to be performed.


In addition, there are restrictions to what personal articles may be worn in the restrictive approach boundary:


NFPA 70E 2015 130.6(D) Conductive Articles Being Worn. Lists the following examples of conductive articles which may not be worn:

  • watchbands
  • bracelets
  • rings
  • key chains
  • necklaces
  • metallized aprons
  • cloth with conductive thread
  • metal headgear
  • metal frame glasses

This applies to anywhere they may come in contact with exposed energized electrical conductors or circuit parts. OSHA also makes a similar provision that must be adhered to.


Figure 1: Arc Flash Suit

Courtesy of Dean Thomas, GTRI

Personal Protection Equipment Selection

What determines the appropriate PPE?

The type of PPE required depends on the minimum arc rating as determined by the flash hazard analysis results, the incident energy levels expressed as calories per square centimeter (cal/cm2) expected to be encountered at specific distances.

Arc-Rated vs. Flame-Resistant PPE

All protective clothing and equipment used for the protection from an arc flash event must be "arc-flash" rated and labeled as so by the manufacturer. In previous releases of the NFPA 70E, the term "flame resistant" had been used but is now removed to clarify that the only acceptable rating that will be allowed is the arc flash level. Using the flame resistant term could imply that using PPE made from these materials is adequate when in fact they are not. Note that this refers to arc flash/electrical shock protection and does not rate for arc blast. All arc-rated garments or equipment are always flame resistant—but not all flame resistant garments and equipment is arc-resistant.

A way of identifying arc-rated articles is the cal/cm2 rating on the label.

The OSHA "269" standard (1910.269(l)(6) ) which applies to all work involving electric power transmission, or distribution lines and equipment, whether it be general industry or construction work:

  • Requires that workers be trained in the potential hazards of electric arcs and the flames they can produce by igniting other materials in the area.
  •  Prohibits workers from wearing clothing that, in the presence of an arc, can potentially increase the extent of injury; that is, if the clothing would ignite and continue to burn, or if it melts on the skin. Thus, workers are generally prohibited from wearing clothing materials made entirely of, or blended with, synthetic materials such as acetate, nylon, polyester, or rayon.

Note that the NFPA 70E 2012 130.5 (B) standard applied the Hazards Risk Categories for item (2) which was replaced for 2015 with the article shown below:


NFPA 70E 2015 Article 130.5(C) Arc Flash PPE. One of the following methods shall be used for the selection of PPE. Either, but not both, methods shall be permitted to be used on the same piece of equipment. The results of an incident energy analysis to specify an arc flash PPE Category in Table 130.7(C)(16) shall not be permitted. (1) Incident Energy Analysis Method. (2) Arc Flash PPE Categories Method. (NFPA 70 E 2015)

(1) Incident Energy Analysis Method. The incident energy exposure level shall be based on the working distance of the employee's face and chest areas from a prospective arc source for the specific task to be performed. Arc-rated clothing and other PPE shall be used by the employee based on the incident energy exposure associated with the specific task. Recognizing that incident energy increases as the distance from the arc flash decreases, additional PPE shall used for any parts of the body that are closer than the distance at which the incident energy is determined.

(2) Arc Flash PPE Categories Method. The requirements of 130.7(C)(15) and 130.7(C)(16) shall apply when the arc flash PPE category method is used for the selection of arc flash PPE.



Figure 1: Various Arc Flash PPE

Courtesy of Dean Thomas, GTRI 


Figure 2: Arc Flash Suit 40cal/cm2 Label

Courtesy of Dean Thomas, GTRI

Selecting Appropriate FR Clothing

Most severe burn injuries and fatalities are caused by non-flame resistant clothing igniting and continuing to burn.

Clothing made from 100% cotton or wool may be acceptable if its weight is appropriate for the flame and electric arc conditions to which a worker could be exposed. As heat levels increase, these materials will not melt, but they can ignite and continue to burn. The amount of heat required to ignite these materials is dependent upon a number of factors, including the weight, texture, weave, and color of the material. This type of clothing does not comply with the "269" standard if it can ignite (and continue to burn) under the electric arc and flame exposure conditions found at the workplace. If they do not choose FR clothing, employers need to make a determination of whether or not the clothing worn by the worker is acceptable under the conditions to which he or she could be exposed. FR clothing is acceptable with respect to the OSHA apparel requirements.

NOTE: Clothing made from the following types of fabrics, either alone or in blends, is prohibited by this paragraph, unless the employer can demonstrate that the fabric has been treated to withstand the conditions that may be encountered or that the clothing is worn in such a manner as to eliminate the hazard involved: acetate, nylon, polyester, rayon.

The fit of FR clothing is important to the safety of the worker. When the surface of FR clothing is heated, heat is conducted through the material; and any FR clothing touching the skin can result in a burn.

It is recognized that employees typically provide part or all of their own work clothing. However, no matter who provides the clothing employees wear, the employer is responsible for ensuring that the flame resistance or flame-retardant-treated conditions of apparel worn by an employee who is exposed to the hazards of electric arcs or flames are maintained whether made from natural materials of appropriate weight or made from synthetic materials. The flame resistant or flame-retardant-treated properties of apparel can be compromised if the garment is incorrectly laundered or repaired and, in any case, will diminish to the point of ineffectiveness after many washings. Since the employer is responsible for ensuring that apparel remain flame resistant or flame-retardant-treated, the employer may wish to instruct his or her employees as to appropriate laundering.

Arc Rated Clothing

OSHA generally requires protective clothing and other protective equipment with an arc rating greater than or equal to the employer's estimate of available heat energy. As explained earlier, untreated cotton is usually acceptable for exposures of 2 cal/cm2 or less (Arc Flash Boundary minimum requirement is 1.2 cal/ cm2). If the exposure is greater than that, the employee generally must wear flame-resistant clothing with a suitable arc rating in accordance with § 1910.269(l)(8)(iv) and (l)(8)(v).

Arc-rated FR protected equipment/clothing must contain a label or other mark that describes the maximum incident energy rating.

The arc rating of a fabric is either an ATPV (Arc Thermal Performance Value) or an Ebt (Energy breakopen threshold).

Arc Thermal Performance Value (ATPV) is incident energy on a fabric or material that would result in a 50% chance of the onset of a second degree burn as measured in cals/cm2. Higher rated values provide more protection.

Energy Breakopen Threshold value is determined when the incident energy a fabric is exposed to would result in a 50% chance of breakopen occurs before the onset of a second degree burn. Once the fabric or material breaks open, direct exposure to arc flash may result in additional injuries.


Annex H in NFPA 70E 2015 provides guidelines to the proper clothing, personal protective equipment (PPE), and shock protective equipment when either the arc flash PPE category method or the incident energy method is used to perform an arc flash risk assessment.



Figure 1: Poly/Cotton Shirt and Pants Arc Test

Courtesy of Westex® by Milliken®



Figure 2: ATPV Rating Label


Figure 3: An Electrician in Full Arc Flash Suit

Credit: Dennis Schroeder / NREL

Using the NFPA 70E Tables

For determining minimum requirements when using the PPE Categories Method, the NFPA has provided arc flash PPE classifications tables for equipment using AC and DC systems as determined by the level of arc flash hazard exposure. If the task is not listed, it is necessary to use the incident energy analysis method to determine the proper levels of PPE.


The NFPA 70E 2015 Article 130.7(C)(15)(A) Alternating Current (ac) Equipment, states that if used instead of the incident energy analysis method as defined in 130.5(B)(1), determining whether arc flash PPE is required can be done by looking up the task given in Table 130.7(C)(15)(A)(a) as shown in the example in Figure 1. If it determined that arc flash PPE is required for the task, then the appropriate PPE category can be found in Table 130.7(C)(15)(A)(b). These categories are derived from the estimated maximum available short-circuit current, the maximum fault-clearing times, and the minimum working distances for various ac equipment types or classifications.

However, an incident energy analysis is required (as specified in NFPA 70E 2015 Article 130.5) if any of the following apply:

  • The task is not listed in Table 130.7(C)(15)(A)(a)
  • For power systems that have more than the estimated maximum available short-circuit current.
  • For power systems that have longer than the maximum fault clearing times.
  • The task has less than the minimum working distance specified.


In the NFPA 70E 2015 Article 110.1 Safety programs, the principles are defined to promote an awareness of workplace safety and the potential of electrical hazards. The condition of the equipment is an important part of the total electrical safety program (ESP) developed by the employer which includes policy making, proper training, monitoring and maintenance practices. As such, the equipment condition is a deciding factor in whether arc flash PPE is required for the listed tasks.


NFPA 70E 2015 Article 110.1(B) Electrical Safety Program. Maintenance. The electrical safety program shall include elements that consider condition of maintenance of electrical equipment and systems.


PPE Categories Tables

If the criteria is met as described above, then the following tables may be utilized to determine the minimum levels of PPE required.


NFPA 70E 2015 Table 130.7(C)(15)(A)(b) Arc Flash Hazard PPE Categories for Alternating Current (ac) Systems

(See Figure 2)


NFPA 70E 2015 Table 130.7(C)(15)(B) Arc Flash Hazard PPE Categories for DC Current (dc) Systems

(See Figure 3)


Reproduced with permission from NFPA70E®-2015, Electrical Safety in the Workplace, Copyright© 2014, National Fire Protection Association. This reprinted material is not the complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety.


 Table 130.7(C)(15)(A)(a) Arc Flash Hazard Identification for Alternating Current (ac) and Direct Current (dc) Systems.png

Figure 1: Table 130.7(C)(15)(A)(a) Arc Flash Hazard Identification for Alternating Current (ac) and Direct Current (dc) Systems

Click on image to view enlarged version in new browser window. Close the new window to return to this lesson.

Table 130.7(C)(15)(A)(b) Arc-Flash Hazard PPE Categories for Alternating Current (ac) Systems.png

Figure 2: Table 130.7(C)(15)(A)(b) Arc-Flash Hazard PPE Categories for Alternating Current (ac) Systems

Click on image to view enlarged version in new browser window. Close the new window to return to this lesson.

Table 130.7(C)(15)(B) Arc-Flash Hazard PPE Categories for Direct Current (dc) Systems.png

Figure 3: Table 130.7(C)(15)(B) Arc-Flash Hazard PPE Categories for Direct Current (dc) Systems

Click on image to view enlarged version in new browser window. Close the new window to return to this lesson.

What are the different PPE categories?

When reading the arc flash warning label affixed to the affected electrical equipment that will be encountered in the field, the minimum level of PPE required may be expressed as either HRC (Hazard Risk Category) for labels produced to the NFPA 70E 2012 standard or the PPE Category for compliance to the 2015 standard.


2012 PPE Levels

Arc flash categories previous to 2015 were based upon testing and analysis of the hazard and presented by HRC number and incident energy as shown to the right:


Hazard Risk Category (HRC)

Incident Energy

Category 0   (eliminated in 2015)

<1.2 cal/cm2

Category 1

1.2 to 4 cal/cm2

Category 2

4 to 8 cal/cm2

Category 3

8 to 25 cal/cm2

Category 4

25 to 40 cal/cm2

Table 1: Hazard Risk Categories (HRC)

2015 PPE Levels

Arc flash categories for the 2015 are based upon testing and analysis of the hazard and presented by PPE category number and incident energy as shown to the right:


PPE Category

Incident Energy

Category 1

Minimum 4 cal/cm2

Category 2

Minimum 8 cal/cm2

Category 3

Minimum 25 cal/cm2

Category 4

Minimum 40 cal/cm2

Table 2: PPE Categories

Personal Protective Equipment by Category

2012 Standards

Personal Protective Equipment by HCR Level



Personal Protective Equipment by Category

2015 Standards

Personal Protective Equipment by PPE Categories




Personal Protection Equipment Descriptions

NFPA 70E 2015 Articles 130.7(C)(9), (10), and (11) provide detailed guidance for the selection of personal protective equipment to be used for specific tasks and hazard levels.

Eye Protection: Safety glasses meeting requirements of ANSI Z87.1 provide protection from impact and also filter damaging ultraviolet energy. Protective eyewear, in the form of safety glasses, always must be worn under the face shield or hood viewing window. Goggles may be worn only if they have an arc rating.


Figure 1: Safety Glasses

Face Protection: Face shield - nonconductive PPE with wrap-around guarding for the face, neck, and chin. Must have an arc rating at least as great as the predicted incident energy. Must wear eye protection (safety glasses or goggles) under face shield or hoods


Head Protection: Helmet - Nonconductive, arc-rated, head protection (ANSI Z89.1, Class E or G).



Figure 2: Hard Hat with Face Shield and Chin Guard

Balaclava: Minimum arc rated to the incident energy exposed to. Required to be used under a face shield in (HRC 2 for 2012) . Also must be used if the back of the head is exposed within the arc flash boundary.


Hair nets and/or Beard nets: Must be non-melting and flame-resistant.



Figure 3: Face Shield with Balaclava

Arc Rated Hood: Minimum arc rated to the incident energy exposed to. Must be used where incident energy is expected to exceed 12 cal/cm2. May be used instead of arc-rated face shield and balaclava combination.


Figure 4: Double Layer Arc Flash Hood with Hard Hat Inside

Hearing Protection: Hearing protection must be worn while performing work within an AF protection boundary. Ear canal inserts are specifically mentioned because they interfere less with other head or neck PPE than externally worn types.


Figure 5: Hearing Protection

Gloves: For hand protection, arc rated gloves are required made of heavy-duty leather of minimal 0.03 in. (0.7mm) thickness, with or without non-flammable, non-melting materials. Leather gloves are considered arc flash protection up to PPE category 2, however do not offer protection from electric shock.


Additional hand and arm protection (sleeves) against electric shock must be worn UNDER the leather protector gloves. Insulated gloves are arc-rated by tag color with readable information, (not glove color) for the voltage for which the glove will be exposed when working within the flash protection boundary.


The chart in Figure 7 shows the classifications based on maximum usage voltage when worn with leather protectors.


Do not use leather protector gloves alone, always use with the appropriate insulating rubber glove for maximum protection to prevent serious injury or death.


Although not rated for thermal protection, voltage-rated gloves with leather protectors provide significant thermal protection. When the worker's hands are within the flash protection boundary, rubber insulating gloves must be worn with leather protectors. PPE that provides thermal protection offers no acceptable protection from shock or electrocution. Shirt sleeves should fit under the gauntlet of protective gloves to minimize chance that thermal energy could enter the shirt sleeves.

Type I (not ozone resistant) and Type II (ozone-resistant)

Ozone, a form of oxygen that is produced in the air surrounding a high voltages conductor which can damage rubber products such as Type I natural rubber insulating gloves, causing cracks to form making them unsafe to use. Type I rubber gloves can also be negatively affected by UV rays (sunlight) and thus must be properly stored and inspected.

The Type II gloves (typically made from synthetic rubber) although not as susceptible to damage from ozone and UV rays, are not as flexible or comfortable as Type I to wear.


Figure 6: Arc Rated 00 Gloves with Leather Protectors


Figure 7: Voltage Classifications for Arc-Rated Insulating Gloves

Clothing: Arc flash rated within the AF protection boundary and wherever there is possible exposure to an electric arc flash above the threshold incident energy level for a second-degree burn (1.2 cal/cm2). Clothing must cover potentially exposed areas as completely as possible.


Non-melting, non-flame resistant undergarments (such as 100% cotton underwear) may be worn under arc-rated outerlayers as long as they are not exposed to potential arc flash. The innermost arc-rated layer of PPE must not break open, be rolled up or shortened exposing the non-flame resistant material or skin. Non-arc rated Arc-rated undergarments generally provide better system arc rating than non-flammable, non-melting underlayers.


Note that the small amount of elastic material used in non-melting underwear and socks is permissible.


Figure 8: Fire-Resistant, Shirt, Pants, Shop Coat and Coveralls

Arc Flash Suits: Is a complete arc rated clothing/equipment system that may include pants, jacket, coverall and hood to cover the body entirely (except for the hands and feet). Arc flash rated to minimum incident energy level exposed to.


Figure 9: Arc Flash Suits–40 cal/cm2 Protection

Footwear: Shoes with an arc rating are not available. Heavy-duty leather, safety-toed shoes provide some AF protection to the feet. Shoes made from lightweight material should not be selected.


Figure 10: Footwear

IPE (Insulating Protective Equipment

Includes items such as:

  • Insulating (rubber) line hose, blankets, and hoods.
  • Insulating barriers made of fiberglass or phenolic resin.
  • Live-line tools such as hotsticks, switchsticks, and shotgun sticks.
  • Plastic or fiberglass hardcover items that can be installed with live-line tools.

Like PPE (for example, insulating gloves and sleeves), IPE is used to provide workers protection from contacting energized conductors, but unlike PPE it is not worn on the body. Rubber and hardcover IPE items must be rated for the voltage of the parts being covered (phase to ground or phase to phase).


Figure 11: IPE Shot-Gun Grip-All Stick

PPE Care and Inspection

The NFPA 70E Article 130.7(B) Care of Equipment and Table 130.7(C)(7)(c). requirements state that PPE should be inspected before and after each use, and be repaired, cleaned or laundered according to the manufacturer's instructions prior to use. Normal use; the putting on and taking off of PPE clothing and equipment, the damage that may occur to fabric and materials, the laundering and cleaning, all eventually contribute to the deterioration and shorten the expected lifespan. Certain PPE must be periodically inspected and recorded to ensure they remain in a safe, reliable condition, and if found not to be, immediately removed from service and replaced.


Note that even a pin size hole in PPE can allow electrical energy to penetrate or diminish its overall effectiveness.


Arc Rated FR Clothing

Inspect arc rated FR clothing, per the manufacturer's instructions, visually before each use to ensure that the clothing is not soiled or contaminated with grease, oil, flammable liquid, or combustible materials.

  • The clothing must be free from tears, cuts, or rips.
  • Check if the rating of the FR clothing is voided (presence of materials discussed above).


  • Visual inspection
  • Inflation
  • Reverse glove, inspect inside (repeat inversion)
  • Store in appropriate bag
  • Glove conditioners prolong the effectiveness
  • V-rated gloves must be inspected prior to use by the user and be tested/certified every 6 months.
  • Moisture absorbing powders may be used to improve safety and comfort.

Other PPE Equipment: Follow manufacturer's recommendations.


PPE must be stored in a manner to prevent physical damage and damage from moisture, UV rays, dust, or other deteriorating agents or contamination from flammable or combustible materials.

  • Consult manufacturer's recommendations
  • Utilize manufacturer provided storage containers

Cleaning, Repairing and Affixing Items

Arc rated FR clothing and other arc-rated PPE must be maintained in a clean and sanitary condition and must be cleaned and maintained as defined by the clothing manufacturer.

  • Workers laundering their own PPE must follow those instruction that generally require different wash/rinse cycles than are used for household washing.
    • FR clothing may have restrictions on temperature settings, use of bleaches and hydrogen peroxides, starch and fabric softeners.
  • When using a laundry service, the laundry facility must be aware of the FR clothing manufacturer's laundering instructions that must be implemented with regard to retaining the FR characteristics.
  • If FR clothing is shared by workers, consider health aspects of shared PPE when determining cleaning frequency.
  • When FR clothing is repaired, the same FR materials used to manufacture the FR clothing shall be used to complete repairs.
  • Do not attach or affix any metallic or non-metallic items such as labels, pins, emblems, etc., to PPE unless authorized to do so.
  • When trim, name tags, patches or labels are affixed to FR clothing, guidance in American Society for Testing and Materials (ASTM) F 1506, Standard Performance Specification for Textile Material for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electric Arc and Related Thermal Hazards, shall be followed. They also must be made of arc-rated, FR material.



Figure 1: Gloves and Glove Storage Bag



Figure 2: Insulated Glove Inflator

Preventing Arc Flash

How do you protect against arcing faults?

Unfortunately, it is impossible at this time to devise an electrical system that is completely "flash-proof", although significant efforts have been made.

However, personnel working on a system can take precautions to help protect themselves from the hazards associated with an arcing fault.

The National Fire Protection Agency (NFPA) requires that before a worker approaches exposed electrical conductors or circuit parts that have not been placed in an electrically safe work condition, a flash analysis must be performed. This analysis is to determine the flash protection boundary and the level of personal protective equipment that the worker must wear.


Complete the Quiz Me activity below.


Figure 1: Use Proper Level of PPE

 Toggle open/close quiz question

Be Aware of the Established Flash Protection Boundaries (FPB) and Procedures

The "Limited Approach Boundary" is the limit of approach distance for unqualified persons, that is, those less capable of recognizing a shock or flash hazard, to be near a live part.


The "Restricted Approach Boundary" should never be crossed by any unqualified person. Even qualified people must have an approved work plan and use personal protection equipment approved for those work conditions.


The "Prohibited Approach Boundary" (removed in 2015) is the minimum approach distance to an exposed energized conductor and is the closest point to prevent flashover. In order to cross into prohibited space, qualified personnel must do all of the following:

  • Be specifically trained to work on energized conductors or circuit parts.
  • Have a documented plan that justifies the need to work inside the prohibited approach boundary.
  • Perform a hazard risk analysis.
  • Have both the documented justification plan and the hazard risk analysis approved by the site manager.
  • Wear personal protection equipment as if they would be in direct contact with the energized part.

It is against the law for anyone other than a trained Electrician or authorized person to perform such work requiring levels of PPE and training NOT allocated to the work member and/or team leader level.


Only an Electrician can go into an electrical panel!


This and other citations within NFPA 70E make it clear that these references are referring to trained electricians.

  • You can do minor maintenance outside of the panels.
  • You have received training on Arc Flash/Blast and ECPL.


As a result of this training you do not have the authority to enter into an Electrical Panel.



Figure 1: AIMSS Arc Flash Boundaries

Establishing an Electrically Safe Work Condition

NFPA 70E 2015 Article 120 Establishing an Electrically Safe Work Condition provides the requirements and specifications of an employer provided lockout/tagout procedure to safely de-energize and re-energize electrical as well as other sources of energy. It also requires that all stored energy which is outlined in the requirements for the released of stored electrical or mechanical energy that might endanger personnel, includes the requirement that before the equipment is touched or worked on, all capacitors be discharged, and that high capacitance elements are short-circuited and grounded. A key element to the lockout/tagout procedure is to verify that the energy source, stored or otherwise, is dissipated.

Proper method to operate electrical panel disconnect:

  • Remove as much of the electrical load as possible prior to operating a disconnect.
  • Utilize a proper stance and position of your body and head, standing to the side of the panel.
  • Place your hand on the electrical disconnect and look away from the panel door.
  • Operate the handle.
  • Submit a maintenance ticket if a disconnect is faulty, or an ECPL label is incorrect or damaged.

View Video 1 to see an electrical Lockout/Tagout procedure performed.



June 8, 2014 - Taconite mine – A mine electrician did not lock out a 4160-volt starter/disconnect when testing a circuit with a 600-volt meter. The safety device that prevents the starter door from being opened when the system is energized had been defeated. The electrician was burned from the arc flash that occurred when he contacted bare metal conductors inside, and the meter "blew up" in his hands. The electrician, who was not wearing proper protective gear, was hospitalized with burns to this hands and face.


Video 1: Electrical Lockout/Tagout Procedure

( No Audio)

Do's and Don'ts

  • Open electrical panels present exposure hazards. Close whenever possible.
  • Do report broken or damaged panel doors.
  • Do exercise caution closing a door. If you think closing an Electrical Panel Door poses an electrical hazard, contact the appropriate personnel to close it.
  • If a person becomes energized, that person must be safely separated from the electrical power, or the electrical power shut off or removed.
  • Remove the current source by operating the disconnect. Time is short, prolonged exposure to electrical shock causes increased personal damage.
  • Do not touch the person who is in contact with electricity.
  • Do not reach blindly into areas that might contain live energized equipment.
  • Do not distract or put yourself in a position that might distract another person working on energized equipment. Looking over an Electrician's shoulder while he/she is working in an Electrical Panel is a dangerous practice that could put you and the Electrician's life in danger.
  • Do illuminate areas to help provide a safe work environment.
  • Do keep the areas in front of electrical equipment clear.
  • Do remove conductive articles of clothing or jewelry such as watches, bracelets rings necklaces before starting work.
  • Do use only properly insulated tools rated for the Approach Boundary area where work is to be performed.
  • Do avoid touching or leaning on equipment that could potentially be energized or come in contact with energized equipment (metallic surfaces).
  • When operating switchgear (energizing or de-energizing): switch remotely if possible, stand aside as much as possible if manually switching, using proper PPE.
  • Never assume that you know how a circuit is wired. Ask for help and/or consult a wiring diagram/schematic if you are unsure.
  • Apply lockout / tagout devices in accordance with established policy, your lock is your PERSONAL key to staying ALIVE! Always use your own lock. Never have someone else do it for you.
  • Always TEST to ensure there is no voltage inside an electrical enclosure prior to working on it. Use adequately rated equipment to test each phase conductor phase-to-phase and phase-to-ground. Before and after each test, determine that the voltage detector is operating satisfactorily.
  • Do not bypass or defeat electrical safety devices or circuitry.


Figure 1: Arc Flash

Courtesy of EWB Engineering, LLC

What Will Help Keep You Safe

What you do.

  • Always follow proper ECPL procedures.
  • Lock out all power – it's your right, it's your life!
  • Be familiar with your work area and associated hazards.
  • Proper positioning for operating a disconnect.

What do you see.

  • Damaged or worn electrical components.
  • Open panels.
  • Wet floors and poor housekeeping.

What do you hear.

  • Buzzing or crackling sound.
  • Call for help.

What do you feel.

  • Abnormal heat.

What do you smell.

  • Burning or hot odor.



Figure 1: Arc Flash PPE

Safety Devices

These devices are mainly effective for general electrical work and may not prevent an arc flash incident from occurring.

Warning Indicator Light

For safety, all metal on machines should be tied to ground (a wire fastened from the metal to a copper rod driven into the earth). Thus, if a wire should come loose/break and touch any metal surface, current will flow (be shorted) to ground, tripping a safety device in the cabinet. If the metal parts of a machine were not tied to ground and a "live" or "hot" wire were to touch the metal, then the machine would become "live". If a person were to touch the machine, they would complete the circuit to ground (through their body) and could be electrocuted.

Some electrical panels are equipped with ground indicator lights:

  • Dimly lit Indicator Lamps indicate that the circuit is properly grounded.
  • A possible ground fault problem exists if:
    • One Lamp is bright and the other is dim or out, indicating that the circuit is going to ground somewhere outside the panel.
    • Both lights are out.

Current Limiting Fuses/Circuit Breakers

Current limiting fuses and circuit breakers, when operated in the current limiting range, operate extremely fast to reduce the arcing current and diminish the energy levels produced.

  • Only help mitigate hazard if current is high enough to blow or trip.
  • Do not mitigate the duration (cycle times) of arc flash.

Ground Fault Circuit Interrupters (GFCI)

An electrical wiring device that disconnects a circuit whenever it detects that the flow of current is not balanced between the phase ("hot") conductor and the neutral conductor.

  • The presumption is that such an imbalance may represent current leakage through the body of a person who is grounded and accidentally touching the energized part of the circuit.
  • A shock, possibly lethal, is likely to result from these conditions; GFCIs are designed to disconnect quickly enough to prevent such shocks.


In NFPA 70E 21015 Article 110.4(C)(2) Maintenance and Construction (GFCI) Protection:

  • GFCI protection provided for operating or using tools related to maintenance and construction activity 125-volt, 15-, 20-, or 30-ampere circuits.
  • Greater than 125-volt, 15-, 20-, or 30-ampere circuits either GFCI protection or an assured equipment grounding conductor program.

When to Use

Ground fault circuit interrupters should be used any time electrical equipment is used around moisture. This would include the use of electrical power tools outdoors or in damp locations.

How to Use:

  • Before use, test and reset to verify proper operation.
  • Always follow manufacturer's recommendations.

Infrared Scans

Infrared cameras are one of the tools used to identify problems in electrical systems by detecting the IR wavelengths generated by heat. An infrared camera can be used to identify a failing component prior to a complete failure which can cause electrical system shutdown, equipment damage and bodily injury. Although they can be used to inspect electrical components at a distance, they do require a direct line-of-sight to record accurate images which often requires a qualified worker, wearing appropriate PPE and trained for the task, to open the enclosure to gain access.

Infrared Window

An infrared window installed on an electrical cabinet or panel may eliminate the risks of performing a live inspection it allows the infrared camera a direct line-of-site access to the interior components without having to open the enclosure. This provides an safe alternative to having a qualified person open doors or remove access panels, a source of triggering an arc flash event.


Figure 1: Ground Indicator Lights on Electric Panel



Figure 2: Class J Fast Acting Current Limiting Fuses in AMTEC Simulator Electrical Panel



Figure 3: Panelboard Mount and Portable GFCIs



Figure 4: Using Infrared Device to Troubleshoot at a Distance

(workers may use FR level clothing outside the Limited Approach Boundary)


Used with safety warning signs to limit access and/ or to prevent entering or exiting an area where work on energized electrical work is to be performed. They must not be placed closer than the limited approach boundary. If the arc flash boundary is larger than the limited approach, then it is placed no closer than the larger of the two.

Should not be placed where it could interfere with entering or exiting an area in the event of an arc flash incident.

Barricades must not be made of conductive materials where likely to increase the hazard of electrical exposure.

To protect an unqualified person from entering the limited approach boundary utilize one or more of the following:

  • Barrier tape: Clearly marked.
  • Orange cones
  • Signage: Properly worded
  • Plastic Chain: Non-conductive.
  • Attendant: To warn other personnel approaching the area.



Figure 1: Barrier Tape and Plastic Chain

AMTEC Integrated Manufacturing System Simulator ESWC and Voltage Test

Let's put all of this information to practical use. Using the AMTEC Integrated Manufacturing System Simulator we can run through a typical procedure to put the equipment into a Electrically Safe Working Condition (ESWC):

Identify the equipment to be worked on:

AMTEC Integrated Manufacturing System Simulator


Electrical Energy Sources:

  • Primary power source: 480 VAC, three-phase
    • 208 VAC, three-phase
    • 120 VAC, single-phase
    • 24 VDC
    • External (auxiliary) power distribution is via disconnect/lockouts at the rear of the control panel to remote components

Pneumatic Energy Sources:

  • 70 PSI (nominal value)

Hydraulic Energy Sources:

  • 300 PSI (nominal - unloader motor)

Kinetic Energy Sources: Always present during operation.

Potential Energy Sources: Charged capacitors, hydraulic hoses under pressure, etc.

Arc Flash Label

Let's review the following information on an Arc Flash label:

  • System Voltage: 480 Volts
  • Incident Energy: _____
  • Arc Flash Boundary: 48 inch
  • Limited Approach Boundary: _____
  • Restricted Approach Boundary: 12 Inch
  • Appropriate PPE Required: Category 2

The Arc Flash label shown in Figure 2 is for a particular AIMSS installation which depicts a Category 2 Arc Flash PPE rating as a result of an Arc Flash Risk Analysis performed by a qualified person. This is determined by several factors including available voltage and upstream current limiting device clearing times. Since the PPE category level was stated, the optional incident energy level was not required. The label displays the Restricted Approach Boundary as "Shock Protection Boundary" and does not indicate the Limited Approach Boundary, which are not minimum required elements of an Arc Flash label. Note that each equipment installation is different and no single label can provide the necessary information for all similar equipment.

PPE Category Level 2 Equipment Required:

According to this Arc Flash label, the equipment is rated at an system voltage of 480 VAC and an Arc Flash Protection Boundary of 48 Inches, specifies a Category 2 level of PPE:

  • Arc-Rated Clothing, Minimum Arc Rating of 8 cal/cm2 (as defined in the NFPA 70E Article 100)
  • Arc-rated long-sleeve shirt and pants or arc-rated coverall
  • Arc-rated face shield (wraparound to protect the back of the head and neck) or arc flash suit hood
  • Arc-rated balaclava
  • Arc-rated jacket, parka, rainwear, or hard hat liner (as needed)

Protective Equipment:

  • Hard hat (non-conductive, Class E or G)
  • Safety glasses or safety goggles (must be worn)
  • Hearing protection (ear canal inserts)
  • Minimal 00 insulating rubber gloves with leather gloves protectors
  • Leather footwear

NOTE: Non-melting, non-flame resistant undergarments (such as 100% cotton underwear) may be worn under arc-rated outerlayers as long as they are not exposed to potential arc flash.

ESWC and Test Verification:

(1) Notify any affected personnel that the equipment will be de-energized and locked out.

(2) Using the Energy Control and Power Lockout (ECPL) placard on the main electrical control panel, locate and identify all power sources and their disconnecting devices (use up-to-date drawings if necessary). Make sure the device used to disconnect and lockout the power source is properly identified to the ECPL sign.

Ensure all potential energy sources to be de-energized are identified as well.

On the AIMSS, the a following devices will need to have their potential energy dissipated, bleed off or blocked out if working in these areas:

  • Electrical Panel: VFD drive - allow time to dissipate electrical energy (indicator light turns off to show when discharged)
  • Conveyor System: Load Conveyor Transfer Stop Cylinder springs
  • Conveyor System: Unload Conveyor Pusher Stop Cylinder springs
  • Conveyor System: Robot: springs on suction cups
  • Conveyor System: Hydraulic Motor- hydraulic fluid pressure in hoses
  • Conveyor pneumatic equipment: air lines/DCVs/cylinders

(3) Make sure the equipment is in a non-operational state at the control panel. Use the normal operating shut-down procedure it the equipment is in operating mode.

(4) De-energize the simulator. (NOTE: For the purposes of this training and to ensure the safety of the students and faculty, disconnect the external switch mounted on the side of the simulator cabinet, upstream (line side) of the main electrical disconnect on the panel. Make sure to follow the same procedures as when disconnecting any power source.)

To do this, stand off to the side and place the main electrical disconnect switch to the OFF position.

(5) Apply a properly identified lockout device (padlock) to the disconnect according to a documented policy. Ensure the key remains in your possession at all times. The person who placed the lockout device is responsible for its removal.

(6) Disable, restrain or dissipate all potential energy sources (discharging, disconnecting, bleeding off, etc.). Identify the possible sources of stored electrical energy (example: capacitors) and ground the phase conductor or circuit parts.

Note that only those devices in the area in which the work needs to be performed have to be de-energized and locked out.

(7) The next step is to verify the equipment is de-energized. Ensure that no personnel are near the affected equipment, then try to operate by pressing the operating controls (push button, switch, etc.). Verify the equipment is de-energized by verifying with a test instrument capable of detecting voltage. Important: Place the equipment into the "OFF" or non-operational mode after operational verification is complete.

Make sure the testing instrument (volt meter) and its accessories are rated for the maximum working voltage and designed for the conditions in which they will be used.

For example: the AIMSS is rated for 480 VAC, add 5% for a safety margin, the minimal system voltage is 504 VAC, a voltage meter rated for up to 600 VAC minimum is required.

It is mandatory to verify the test instrument (volt meter) prior to use to check for the presence or absence of voltage, and again after checking, by verifying it against a known voltage source.

Once donned with the appropriate PPE, test the equipment for the presence or absence of voltage using the following steps:

Step 1: Test the instrument against a known voltage (such as a wall socket or extension cord). It must indicate the known voltage to verify the test instrument is operating properly.

Step 2: Immediately test the equipment for a de-energized state (<1V - stray voltage). Test for voltage to ground and voltage between conductors (phase to phase).

For the AIMSS this would be performed at the Main Disconnect Switch:

  • Phase 1 to 2
  • Phase 2 to 3
  • Phase 3 to 1
  • All phases to ground

Step 3: Confirm the test instrument for failure by retesting at the known voltage source(such as a wall socket or extension cord). It must indicate the known voltage to verify the test instrument is operating properly.

(8) The equipment is now locked out.

Remember to treat all electrical circuits and parts as energized until ALL sources of energy are accounted for and de-energized.


The process as previously described will place the equipment into an Electrically Safe Working Condition (ESWC) to work on without PPE. This would be applicable if changing wiring, adding a PLC module, changing a VFD drive, or similar task.


To re-energize the AMTEC Integrated Manufacturing System Simulator:

(1) Replace all guarding, covers, circuit protectors that may have been removed during service. Remove all non-essential items from the area.

Close all panel doors and secure with locking handle or screws.

(2) Confirm that all personnel are notified of the impending re-energizing and are safely positioned away from the affected equipment.

(3) Verify the controls are in a safe non-operating mode.

(4) Remove your lockout device. If there is more than one device attached, do not remove them and skip the next step. Remove any energy isolating devices. It may be necessary to remove some types of blocking after re-energization.

Standing off to one side, place the disconnect switch into the ON position. The equipment is now energized and should be treated as such.

(5) Notify affected employees that the servicing or maintenance is completed and the machine or equipment is ready for use.

Exit the arc flash boundary and remove PPE.


Additional Considerations:

There are three external power distribution cables and disconnects/lockouts at the rear of the control panel to remote components on the conveyor system that will be de-energized when the main electrical disconnect is disabled. They can be used to disable power downstream of the main control panel if necessary.

They are identified as follows:

  • Blue - Robot/Robot Controller power
  • Red - Hydraulic Motor power
  • Black - Load Conveyor Motor power

The robot control panel (on some units) have a separate electrical disconnect which will disable power to the controller unit and robot. However, be aware that power may remain on for certain safety circuits. Robot controller may be locked out at the main control panel disconnect switch, safety switch or external power distribution cable disconnect (blue).


Any troubleshooting and testing of the equipment with the power ON and within the arc flash/shock boundaries is only allowed with the proper PPE and training. 


Figure 1: AIMSS - AMTEC Integrated Manufacturing System Simulator


Figure 2: AIMSS Category 2 PPE Arc Flash Label Example



Figure 3: AIMSS Main Electrical Lockout Switch and ECPL Sign



Figure 4: AIMSS Dissipate/Disable Energy Sources



Figure 5: AIMSS External Main Electrical Disconnect Switch



Figure 6: AIMSS Verify LOTO–Attempt to Start at Control Panel



Figure 7: AIMSS Main Disconnect Switch and Distribution Block



Figure 8: AIMSS External Power Disconnects/Lockouts

Available Resources

The following are resources for finding additional information regarding arc flash, regulations and the related PPE. Please note that this list is not all inclusive:

Government Agencies

Occupational Safety and Health Standards, 29 CFR, Part 1910, Subpart S,

Electrical, Occupational Safety and Health Administration (OSHA)


Regulatory Agencies

NFPA 70E Standard for Electrical Safety in the Workplace - 2012 and 2015, National Fire Protection Association (NFPA), Quincy, MA

NFPA 70 NEC® National Electrical Code® 2014, National Fire Protection Association (NFPA), Quincy, MA


IEEE Guide for Performing Arc-Flash Hazard Calculations, IEEE Standard 1584-2002, Institute of Electrical and Electronics Engineers, New York, NY


American Society of Testing and Materials (ASTM), West Conshohocken, Pennsylvania

  • ASTM D120 Standard Specification for Rubber Insulating Gloves
  • ASTM D1051 Standard Specification for Rubber Insulating Sleeves
  • ASTM F478 Standard Specification for In-Service Care of Insulating Line Hose and Covers
  • ASTM F479 Standard Specification for In-Service Care of Insulating Blankets
  • ASTM F496 Standard Specification for In-Service Care of Insulating Gloves and Sleeves
  • ASTM F696 Standard Specification for Leather Protectors for Rubber Insulating Gloves and Mittens
  • ASTM F1236 Standard Guide for Visual Inspection of Electrical Protective Rubber Products
  • ASTM F1449 Standard Guide for Industrial Laundering of Flame, Thermal, and Arc Resistant Clothing
  • ASTM F1505 Standard Specification for Insulated and Insulating Hand Tools
  • ASTM F1506, Standard Performance Specification for Flame Resistant and Arc Rated Textile Materials for Wearing Apparel for Use by Electrical Workers
  • ASTM F1891 Standard Specification for Arc and Flame Resistant Rainwear
  • ASTM F2178 Standard Test Method for Determining the Arc Rating and Standard Specification for Eye or Face Protective Products
  • Exposed to Momentary Electric Arc and Related Thermal Hazards,
  • ASTM F2249, Standard Specification for In-Service Test Methods for Temporary Grounding
  • Jumper Assemblies Used on De-Energized Electric Power Lines and Equipment
  • ASTM F2757, Standard Guide for Home Laundering Care and Maintenance of Flame, Thermal and Arc Resistant Clothing


ANSI American National Standards Institute, Washington, DC Headquarters

  • ANSI Z87.1, Practice for Occupational and Educational Eye and Face Protection
  • ANSI Z89.1, Requirements for Protective Headwear for Industrial Workers
  • ANSI Z535, Series of Standards for Safety Signs and Tags



Consult the equipment specifications, manuals, for information regarding equipment ratings, hazards, safety, operational and maintenance.


Professional Arc Flash Training Providers

Many to choose from, start with your company's Human Resources department.



Many resources available but use with caution, contrary to popular belief, not everything you see on the internet is true (or up-to-date). Most, if not all of the regulatory agencies, safety organizations and training providers have an online presence with information available—some at little or no cost.




While the intent here was to introduce arc flash/blast information and make aware the dangers involved with servicing electrical equipment, it is not intended to intimidate the worker, but instill a healthy sense of respect for the power of electricity. Through proper training, equipment maintenance, selection of the appropriate PPE, safety regulations and programs, the electrical technician should have gained the confidence that they have the tools at their disposal to perform the task at hand safely.

  • Arc flash is something you cannot see, hear, feel, smell, or taste it before it happens.
  • Don't need to fear electricity, but you do need to respect it.
  • Arc flash impacts you financially – loss of time/medical bills/possible long term recovery or disability.
  • Arc flash impacts you, your family, friends, and co-workers emotionally.
  • PROTECT YOURSELF – Remember, ultimately we are responsible for our own safety.



Figure 1: Protect Yourself from Arc Flash


Assess your arc flash knowledge by answering the questions in the Quiz Group below.

 Question 1

 Question 2

 Question 3

 Question 4

 Question 5

 Question 6

 Question 7

 Question 8

 Question 9

 Question 10

 Question 11

 Question 12

 Question 13

 Question 14

 Question 15

 Question 16

 Question 17

 Question 18