Compliance News: Electrical Arc Flash Safety: Why is it important?

By David Stymiest, PE, FASHE, CHFM, GBE


With the release of the 2009 edition of NFPA 70E®, Standard for Electrical Safety in the Workplace®, increased attention is being focused on electrical power system safety and the dangers associated with electrical arc flashes.

According to CDC’s National Institute of Occupational Safety & Health (NIOSH), electricalhazards cause more than 300 deaths and 4,000 injuries in the workplace each year. Someelectrical injuries are instantly fatal, while up to 40% of electrical injuries are ultimately fatalaccording to a paper written by three critical care physicians and referenced in a recent electrical industry magazine article. A research and consulting firm specializing in workplace injuries hascompiled often-quoted statistics indicating that five to ten reported electrical equipment arc flash explosions occur per day in the USA.


An arc flash is basically a short circuit through the air. It is very destructive and dangerous. When an arc flash occurs, a large amount of concentrated heat and blast energy explodes outward from the electrical equipment. Injuries include severe burns from the superheated ball of gas and molten metal, other injuries from the flying shrapnel, hearing damage from the powerful pressure waves, and eye damage from the high-intensity flash. Studies indicate that the temperature of the arc plasma center often reaches 35,000○ F, which is roughly three to four times the temperature at the surface of the sun.

Arc flash events, or arcing faults, are commonly caused by careless cover or device removal, a foreign object such as a tool dropped into energized equipment, parts failure such as the misalignment of moving contacts, dirt contamination or dielectric breakdown, or entry of a foreign body such as an animal.

According to an OSHA letter reprinted in an industry safety bulletin, OSHA considers NFPA 70E® to be “a recognized industry practice. The employer is required to conduct hazard assessment in accordance with 29 CFR 1910.132(d)(1). If an arc-flash hazard is present, or likely to be present, then the employer must select and require employees to use the protective apparel.”