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®