An arc flash is a high-energy electrical fault that produces an explosive release of heat, light, and pressure when a phase-to-phase or phase-to-ground short occurs in equipment energized above roughly 240 V. Incident-energy calculations under IEEE 1584 determine the minimum personal protective equipment rating required for a given task — typically a category 2 to 4 arc-rated suit, balaclava, and face shield. Engineering controls (current-limiting fuses, arc-resistant switchgear, remote racking) reduce both probability and severity. Documented compliance with NFPA 70E has measurably lowered injury rates in jurisdictions that enforce it.