Written by Steve Hudgik
PPE includes cotton and flame-resistant (FR) clothing, voltage-rated gloves, hard hats with full-face shields, full-coverage flash suits, and insulated blankets. PPE is necessary whenever a worker crosses the Flash Protection Boundary, but the type and amount of PPE required varies with the hazard.
All clothing worn around live circuits should be 100% untreated natural fiber. Synthetic materials such as nylon or acetate will melt onto skin in the event of an arc flash or electric shock, increasing the risk of serious burns.
NFPA 70E section 130.7(C)(1) requires all workers within the Flash Protection Boundary to wear PPE. However, arc flash can occur and cause injury even when no live parts are exposed (meaning that no FPB exists). NFPA 70E Table 130.7(C)(1)(a) lists appropriate PPE for use in such cases.
Too little PPE exposes a worker to potentially lethal injury. On the other hand, high levels of PPE are extremely bulky, and may restrict vision and movement, increasing the chance of an accident as well as increasing work time and difficulty.
NFPA 70E defines five risk/hazard categories which determine the proper level of PPE for a given task. The table below lists PPE required at each level. The risk level for a given task is determined either by conducting an arc hazard analysis or by consulting NFPA 70E Table 3-3.9.1, which lists hazard categories for a wide range of tasks.
|Risk/Hazard Category||Incident Energy (cal/cm2)||Examples of PPE Required*|
|0||2 or lower||Non-melting clothing|
|1||2-4||FR shirt and pants|
|2||4-8||FR shirt and pants, cotton underwear|
|3||8-25||FR shirt and pants, FR coveralls, cotton underwear|
|4||25-40 and higher**||FR shirt and pants, full-coverage flash suit, cotton underwear|
* Other combinations are possible; see NFPA 70E for details. Safety boots, face shields, and leather over voltage-rated gloves should be worn.
** Incident energy levels above 40 cal/cm2 require special care to de-energize equipment when possible, as they represent the most extreme hazards. Some companies offer PPE rated above 40 cal/cm2, but in general this level of risk is considered impractical to protect against.
The PPE tables provided in NFPA 70E are valid only for limited ranges of available current and fault-clearing times, generally appropriate only for small facilities. In addition, the PPE requirements in the tables tend to be more conservative than what is required by a detailed hazard analysis. Whenever economical, conducting an analysis is preferable to using the NFPA 70E tables.
PPE can protect workers against the risk of incurable burns, but it does little to prevent injury from other causes such as blast pressure, falls, or shrapnel.