Arc Flash PPE Categories
Arc-rated clothing and gear protects you from the burn energy of an arc flash. NFPA 70E groups PPE into categories 1 to 4, each with a minimum arc rating. Picking the wrong category can mean the difference between a minor burn and a fatal one.
- Electrical
- Maintenance
- Safety Managers
What an arc rating means
- An arc rating is how much heat energy a fabric or piece of gear can take before a person would likely get a second-degree burn. It is measured in calories per square centimeter (cal/cm²).
- A higher number means more protection.
- Incident energy is the heat energy a worker could be exposed to at a working distance. The PPE rating must be at least as high as the incident energy.
- Arc-rated clothing is tested to ASTM standards. The label shows the arc rating and the standard. See Arc Flash & NFPA 70E.
The four categories
| PPE category | Minimum arc rating of clothing | Typical PPE |
|---|---|---|
| 1 | 4 cal/cm² | Arc-rated long-sleeve shirt and pants (or coverall), arc-rated face shield or arc flash suit hood, safety glasses, hard hat, hearing protection, heavy-duty leather gloves |
| 2 | 8 cal/cm² | Same as category 1, plus an arc-rated balaclava (or hood) with the face shield |
| 3 | 25 cal/cm² | Arc flash suit: jacket, bib overalls or coverall, arc-rated hood, plus gloves, hearing protection and leather footwear |
| 4 | 40 cal/cm² | Arc flash suit with the highest rating, hood, rated gloves, hearing protection and leather footwear |
These are the general numbers in NFPA 70E. Details of the table and what’s required for each task change with each edition, so use the one your employer follows and the equipment label.
Two ways to choose PPE
- Incident energy analysis: an engineer calculates the energy at each piece of equipment. The label shows the incident energy and the working distance, and you choose arc-rated PPE with at least that rating. This is often the more accurate method, and it can show much higher energy than category 4.
- PPE category method (the table): used when the equipment fits the conditions in NFPA 70E’s tables, such as voltage, available fault current and clearing time. The table assigns a category to each task. If the equipment is outside those conditions, a category can’t be assigned and a study is needed.
Employers must not mix the two methods for the same equipment, and must follow the labels. If a label shows more than 40 cal/cm², no category covers it. Don’t work on it while energized. See Energized Work Permits.
Under the arc-rated layer
- Don’t wear nylon, polyester, rayon, acetate or spandex against your skin or as outer layers. They melt and stick to skin. If the underlayer is not arc-rated, use 100% cotton or a fabric that doesn’t melt, and check your employer’s policy.
- Don’t wear metal jewelry, belts with exposed metal, or flammable items in pockets.
- Don’t add non-rated layers over arc-rated clothing.
- Layering arc-rated garments can increase protection. Use the manufacturer’s documented rating for the combination.
- Button and zip everything, tuck in your shirt and wear the sleeves and legs the right length.
Hands, head, face, ears and eyes
- Voltage-rated gloves protect against shock, with leather protectors over them. See Rubber Insulating Gloves.
- Face and head: arc-rated face shield with a balaclava or a hood, rated for the incident energy. Wear safety glasses under the shield.
- Hearing: ear canal inserts are needed, since the blast can rupture eardrums. See Hearing Protection.
- Fit: clothing must fit and not restrict movement. See Proper PPE Fit.
Care and inspection
- Inspect before each use for holes, tears, burns, stains and worn seams. Replace damaged items.
- Follow the maker’s laundering rules. Don’t use bleach, fabric softener or starch unless allowed. Dirty fabric soaked with oil or grease can burn.
- Repair only with approved arc-rated materials and thread.
- Store clothing clean and dry. See PPE Inspection & Care.
Employer duties
OSHA requires employers to protect workers from electrical hazards and to assess arc flash hazards (for example 29 CFR 1910.335 and 1910.269 for certain work). NFPA 70E is the consensus standard most employers use to meet the rule. Employers must provide the PPE and train workers. See National Electrical Code and Qualified vs. Unqualified.
Before work on or near energized equipment
- Equipment de-energized and locked out if possible. See Lockout/Tagout
- Label read: category or incident energy and the arc flash boundary
- Arc-rated clothing and gear match or exceed the label
- No synthetic or melting clothing underneath
- PPE inspected and clean
- Qualified, trained and following the permit
Standards & references
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