Arc flash safety

Understanding an arc flash label

Learn what each piece of information on an arc flash label means so you can be certain you're taking the right steps to enhance safety in your facility. To help you get started, we've provided this sample label with descriptions below.

Arc flash label key

The owner of the electrical equipment is responsible for providing arc flash warning labels which are required on electrical equipment over 50V that could be accessed while energized.

An arc flash boundary is the distance at which the incident energy equals 1.2 cal/cm², and arc-rated PPE is required for any employee within the arc flash boundary.

The working distance is the distance from a person’s face and chest to the prospective arc source. Typical working distances, primarily based on equipment type, are published in IEEE standard 1584 and used in studies to perform the incident energy calculations.

While performing two sets of calculations for the load side and the line side of the main breaker on specific equipment is not specified in NFPA 70E, Eaton has made this a standard practice to enhance productivity and safety for equipment that has adequate isolation of the main protective device.

Calculated incident energy is the amount of thermal energy (cal/cm²) at a distance from an electrical arc event and indicates the level of PPE required to protect workers.

Nominal voltage, limited and restricted approach boundaries, and PPE glove rating are also displayed on the label to help protect workers from electric shock.

Eaton’s labels display the arc flash study report number for easy reference and label updates.

Why both load-side and line-side calculations matter

If the calculation is performed on the line side only, the entire switchgear lineup may be incorrectly thought to have incident energy above 40 cal/cm² and not able to be worked on while energized. If the calculation is performed on the load side only, the calculated incident energy value may be relatively low, putting workers on the line side in danger. Visibility to both the line and load side calculations can provide greater flexibility for qualified works who understand the isolation of the main breaker in their equipment.

Literature, tools and resources

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