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.

 

ELECTRIC SHOCK MAY NOT APPEAR EXTERNALLY THOUGH INTERNAL DAMAGE HAS OCCURRED AND MAY TAKE DAYS OR WEEKS TO BE NOTICED, WHICH MAY BE TOO LATE. ANYONE EXPERIENCING ELECTRIC SHOCK OF ANY KIND SHOULD SEEK MEDICAL TREATMENT IMMEDIATELY!

 Electrical_Burns.jpg

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

 

Worker_Armpit_Injury.jpg

Figure 3: Worker Armpit Injury