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CREATING AN ARC FLASH LABEL
ARC FLASH PPE CATEGORY
Rather than calculating the incident energy, your facility may choose to use the NFPA 70E Arc Flash PPE Categories. These categories, numbered from 1 to 4, group together equipment of roughly similar hazards and assign a set of required PPE to the entire category. A higher category number represents a higher level of protection needed. The categories are defined in table 130.7(C)(15)(c) in the NFPA 70E
standard.
In the 2012 edition of NFPA 70E,
These categories were called Hazard/
Risk Categories, or HRCs, are included
a category 0 for relatively low-risk
equipment and procedures. The 2015
edition removed category 0, and made
slight adjustments to the requirements.
Older labels that refer to HRCs need to
be updated.
Nominal System Voltage
- 1. Nominal System Voltage - The first label requirement, the nominal system voltage, offers a quick way to assess the potential shock hazard and general degree of danger represented by a system. It can be measured in VAC (volts, alternating current) or VDC (volts, direct current). Common values are 120, 208, 220, and 480, but high-powered systems can use much higher values.
- 2. Arc Flash Boundary - The second label requirement, the arc flash boundary, is the distance from the equipment at which an unprotected person would receive second-degree burns in the event of an arc flash. Specifically, the energy at that point would be 1.2 calories (5 Joules) of heat energy per square centimeter of exposed area, or 1.2 cal/cm². This distance is calculated in a variety of ways, and the calculation method must be documented, although it does not need to appear on the label.
Arc Flash Risk Assessments. To provide effective protection from a hazard, you need to perform a risk assessment. NFPA 70E, 130.5(A) describes a basic risk assessment as having three broad steps:
- Requirements: Assessing Risks
- Once you have determined that a given task being performed will present an arc flash hazard, it’s time to assess the risk involved. How likely is an arc flash, given the type of work being performed and the equipment involved? How much energy would be released in an arc flash if one occurred during that work, and how severe could the worker’s resulting injuries be?
- NFPA 70E, 130.5(F) offers two approaches for this step:
Energy Cost Savings
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Dust traps heat on transformers, switchgear, VFDs, motors, and breakers.
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Clean vents and fans improve airflow and reduce load on HVAC systems.
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Cooler electrical rooms reduce the workload on A/C units.
Cooler electrical rooms reduce the workload on A/C units.
Longer Equipment Life
- Prevents heat‑related damage to insulation, contacts, and circuit boards
- Reduces arcing and tracking caused by dust mixed with humidity or oils
- Extends service intervals and reduces unplanned downtime