Quick Answer
Wear 100% cotton, wool or an FR base layer under FR clothing. Keep polyester, nylon, spandex and polypropylene off your skin: in an arc flash or flash fire they can melt onto you even when the FR shirt holds. Non-melting layers underneath add protection; meltable ones add injury.
What to Wear Under (and Over) FR
| Layer | Wear | Avoid |
|---|---|---|
| Undershirt | 100% cotton or FR tee | Polyester or "moisture-wicking" athletic tees |
| Thermals | Wool, cotton or FR thermal | Polypropylene or poly-blend thermals |
| Underwear and bra | Cotton | Nylon, polyester, spandex blends |
| Neck and head | FR balaclava or neck gaiter | Polyester fleece gaiters |
| Over your FR | FR hoodie, vest or jacket | Regular hoodie or coat |
FAQ
Is cotton flame resistant?
No. Untreated cotton burns, but it leaves ash instead of melting onto skin, which is why it is accepted as an under-layer. Your FR outer layer still has to carry the rating.
Can I wear a moisture-wicking shirt under FR?
Only if it is labeled FR. Most wicking tees are polyester blends.
Are FR base layers worth it?
For cold or long shifts, yes: an FR base layer adds protection and warmth without the melt risk. See how to layer FR for winter.
Build your layers: FR shirts and tees, FR hoodies, all FR clothing, how to wash FR, or our company FR programs.