NFPA 70e

defines and classifies arc flash potential that requires specific apparel to minimize worker injuries.

Arc flash protection clothing is designed to provide a barrier from heat and flame, to minimize total burn injury and to help provide the wearer with extra seconds of protection to help escape possible secondary explosions or fires in the work area.  Arc Flash clothing can increase the chances of survival and decrease the need for medical treatment (skin grafts) and the chances of subsequent infections. It can help preserve the quality of life of a worker exposed to an electric arc event. PPE is not designed to be firefighting gear; it is worn to help reduce the risk of more serious injury. Wearing ordinary clothes, especially synthetic fabrics like nylon, in an electric arc incident may make injuries worse than if the skin was not covered at all. Denim jeans and jackets, cotton shirts, cotton/synthetic T-shirts, sweatshirts, fleeces or nylon jackets are fuel sources that ignite, burn and frequently melt onto the skin. The heavier the weight of the fabric, the more fuel there is to burn. While the explosion may be over in a fraction of a second, but non-flame retardant clothing may keep burning. Remeber, it takes just three seconds to sustain third degree burns.

In electric arc blasts, even FR clothing can break open due to the extreme energy. Its prudent to wear loose-fitting layers, with an FR outer layer, and underwear that won’t melt. Suitable flame retardant ppe will help insulate the wearer from heat, resist breaking open, and will not ignite or continue to burn when exposed to a high intensity, short duration explosion and fire.

NFPA 70-E To help workers understand the burn dangers more easily, the NFPA assigns a 0-4 number to hazard/risk categories representing the danger level. The minimum hazard rating for arc blast puts the burn exposure at 4 cal/cm2, which is a NFPA 70-E “Category 1 Hazard” rating. FR apparel must be worn for the “Category 1 Hazard” level. When selecting an FR garment for electric arc hazards, look for labels that show the arc rating as required by to the ASTM F1506 standard below