OSHA Releases Arc-Flash Guidance
New guidance from OSHA includes recommendations that employers can use to address arc flash hazards within their safety and health programs. Arc flashes, also known as electric arcs, are electrical explosions that produce temperatures greater than 35,000 F—“nearly four times the temperature of the surface of the sun,” the guidance notes—along with shrapnel, concussive forces, and deafening sounds. Items within a three-foot radius of an arc flash are likely to burn, melt, or vaporize, though most injuries from arc flashes result from the ignition of flammable clothing. The frequency of arc flash incidents is uncertain, but the National Fire Protection Association has estimated that up to ten arc flash explosions occur in the United States each day.
OSHA’s guidance identifies several hazards that may lead to arc flashes, including faulty electrical equipment, operating equipment beyond its rated capacity, lack of proper warning systems, and inadequate personal protective equipment. Employers are required to estimate the incident heat energy of electrical conductors or equipment in order to determine the arc flash boundary, which is the distance at which a worker without appropriate PPE could receive second-degree burns. Organizations have developed different methods for calculating arc flash incident energy levels, but some of them may not be applicable in all situations. The guidance recommends that employers use multiple calculation methods and implement the most conservative.
The guidance emphasizes that the arc flash boundary is separate from the restricted approach and limited approach boundaries defined in NFPA 70E, Standard for Electrical Safety in the Workplace. The restricted and limited approach boundaries are intended to protect against electric shock, not arc flash. The arc flash boundary can lie within either the restricted or limited approach boundaries or extend beyond them.
“Whenever there is a likelihood of arc flash incident, employers should determine and use both the arc flash boundary and the limited/restricted approach boundaries to ensure worker safety,” the guidance reads.
OSHA’s guidance includes a discussion of the hierarchy of controls as it pertains to arc flash hazards as well as a table that identifies specific types of arc-rated PPE. For more information, download the guidance as a PDF.