Base Layer Basics

March 23, 2017

It’s clear that arc-rated flame resistant (FR) clothing – shirts, pants and outerwear – is necessary to protect against hazards on-the-job for those that risk exposure to arc flash or flash fire in their everyday work environments.

But what about what you wear underneath, what’s next to your skin? How important is that?

It’s vitally important! Here’s why:

The rules for what to wear under FRC prohibit meltable fibers and fabrics, but allow non-melting but flammable fabrics such as cotton, silk and wool¹. These fabrics eliminate half the problem (melting), but not the other half—potential ignition of a flammable underlayer. In the event the wearer is unexpectedly exposed to a thermal hazard that exceeds the level of protection afforded by the FR clothing, the base layer could come into play – with the potential, depending on the type of base layer, to impact overall protection. What’s best practice?

NEVER wear meltable fabrics (non-FR synthetics or synthetic blends including Tech and Sports garments, 65/35 cotton/poly tee shirts, etc.). These base layers put you at risk because they can burn, melt, and drip against your skin – significantly contributing to injury in the event of arc flash exposure above the arc rating of the outer layer.
Non-melting but non-FR inner layers (such as a 100% cotton tee shirt) are allowed under the standards but may not provide adequate protection in arcs above the arc rating of the outer garment. If breakopen occurs, it exposes the flammable underlayer, which can ignite and continue to burn – significantly adding to injury.
Flame resistant base layers are best, as these provide an added level of protection in the event the thermal hazard exceeds the level of protection provided by the outer layer. As FR and AR fabrics become softer, lighter and quick-dry, FR base layers are rapidly becoming the norm.

So, stay safe – wear FR or 100% natural fiber base layers to accompany your FR outerwear and daily wear!

¹From NFPA 70E, section 130.7 (C) (12) (a).

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