Incident-energy method
What arc rating does your exposure require?
Enter the incident energy from your equipment label or calculation — the cal/cm² value at its stated working distance. The selector returns the required minimum arc rating and the clothing-system class that exposure normally lands in. No brands, no category shortcuts.
The number is on the arc flash label next to its working distance (for example “9.5 cal/cm² at 18 inches”). No label or no calculation yet? Run the free arc flash calculator first — PPE bought before the number is known is a guess.
The rule this selector applies
Under NFPA 70E's incident-energy analysis method, the arc-rated clothing system must have an arc rating at or above the calculated incident energy at the working distance. That single comparison — rating ≥ exposure — is the whole selection rule. The tiers below are commercial stock points, not bands from any standard.
| Calculated exposure | Typical commercial system | Common head/face pairing |
|---|---|---|
| ≤ 1.2 cal/cm² | No AR minimum derived; non-melting clothing floor | Per task assessment |
| 1.2 – 8 cal/cm² | 8 cal/cm² AR daily wear (shirt + pants, or coverall) | AR face shield + balaclava |
| 8 – 12 cal/cm² | 12 cal/cm² AR daily wear | AR face shield + balaclava, or hood |
| 12 – 40 cal/cm² | Arc flash suit (40 cal/cm² common) or tested layered system rated ≥ exposure | Flash suit hood |
| > 40 cal/cm² | Controls first — see above 40 cal/cm² | Engineering decision |
Why no PPE category column: Categories 1–4 come from NFPA 70E's separate table method, where the task and equipment tables assign the category directly within their fault-current and clearing-time limits. Reading a calculated cal/cm² across to a category number is the most common arc flash labeling error — the methods are alternatives for a given piece of equipment. The PPE category method explainer covers when the tables apply; the what cal suit do I need guide covers layering, daily wear versus suits, and garment care.
Common questions
What arc rating do I need for my incident energy?
The arc-rated clothing system's rating must meet or exceed the calculated incident energy at its stated working distance. A 9.5 cal/cm² exposure needs a system rated at least 9.5 cal/cm² — a 12 cal/cm² daily-wear system can satisfy it.
Does my calculated cal/cm² tell me a PPE category?
No. PPE Categories 1–4 belong to NFPA 70E's table method, assigned by the applicable task and equipment table within its limits. A calculated incident energy states a minimum arc rating and is never converted into a category.
When do I need a 40 cal arc flash suit?
When the calculated exposure exceeds what your daily-wear system is rated for — commonly above 12 cal/cm² — and up to 40 cal/cm². Below that, 8 or 12 cal/cm² daily wear covers most calculated panel exposures.
What if the incident energy is above 40 cal/cm²?
Treat it as a controls problem before a clothing problem: de-energize, use remote operation, or cut clearing time with maintenance-mode settings, then recalculate. Higher-rated suits exist, but a result that high should trigger engineering review, not a bigger purchase order.
Can I add two garments' ratings together?
No. Layered garments protect as a tested system with its own system rating; nameplate ratings are not additive. Use a multi-layer system only at the rating it was tested to as a combination.