Arc Flash Basics

NFPA 70E is the National Fire Protection Agency’s standard for the protection of electrical workers against arc flash injuries. Arc flash occurs when electricity jumps, or arcs, from one surface to another. Injuries can occur whenever a person is working on or near energized electrical equipment. Workers can suffer severe injuries or death not only from electric shock, but from severe burns as well. They can also be struck by flying shrapnel. If they are working from a ladder or other elevated surface, an arc flash can cause them to be blown off, causing injuries from falls.


An evaluation known as a Hazard/Risk Category (HRC) Assessment is a necessary element of an arc flash protection program. During this study, each piece of equipment is evaluated by individuals qualified to do the assessment in order to determine the risk level. The equipment then falls into one of four categories, based on the potential energy level of an arc flash, should one occur. The energy is calculated in terms of calories per square centimeter (Cal/cm^2) that a flash could create. The categories are then referred to as HRC 1 through HRC 4. The calories per square centimeter for each category are as follows:
• HRC 1: 4 Cal/cm^2
• HRC 2: 8 Cal/cm^2
• HRC 3: 25 Cal/cm^2
• HRC 4: 40 Cal/cm^2
The higher the category number, the more personal protective equipment (PPE) is needed for live electrical work on that equipment. The lowest category level simply requires a flame retardant shirt and pants while the highest requires multiple layers of protection including a full flash suit.


Arc flash training is critical for any program to be effective at protecting workers from injuries that could occur while working on energized electrical equipment. This, as well as the risk assessment, is where many employers turn to outside resources for help. Organizations like Facility Results have the expertise to assist employers develop a program and conduct training that fully complies with the NFPA 70E requirements. Regardless of how thorough the risk assessment is or how much PPE is on hand, employees will not be protected unless they are trained. A successful training program will ensure workers know how to recognize the hazards and how to protect themselves against them.

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