Avoid These Flammable Fabrics Under Your Flame-Resistant Clothing

28 Nov.,2022


Flame Retardant Knit Fabric

If you work with the potential for extreme dangers like arc flash or flash fire, you should know the importance of flame-resistant (FR) clothing. 

One common question workers have is whether or not it’s


safe to wear base layers


underneath their FR clothing. The answer is that it depends on what materials the base layer is made from.

It protects us from fire-related hazards that could otherwise result in burns and other painful injuries.

Depending on what base layer you choose, you could be enhancing your level of protection. Or, you could be putting yourself at greater risk of injury.

Wait, what?

This news tends to catch a lot of people off guard.

Many people aren’t aware that the materials worn underneath their regular flame-resistant clothing can make or break their own safety. A common misconception is that the outside FR layer is sufficient protection against those risks.


It’s not.

Think about it: Have you ever unbuttoned the top portion of your shirt, and left some skin (or your undershirt) exposed? Or maybe your FR clothing is stretched, worn, has holes or is in need of replacement.

Even if your top layer of FR clothing is in perfect condition and you’re wearing it properly, there’s always a chance that heat from a flash fire or arc flash will find its way to your skin.

Unfortunately, many workers wear these dangerous fabrics beneath their FR gear without even realizing they are putting themselves in danger. Let’s take a closer look at some of the dangers associated with different clothing fabrics.


The Dangers of Synthetic Clothing Under FR Clothing

These flammable clothing fabrics top the list of fabrics to avoid. They are all very similar and made from synthetic materials.


  • Nylon
  • Polyester
  • Spandex

  • Acetate
  • Under-Armour




So, makes them so dangerous? Although these fabrics do not burn quickly or easily, it’s extremely serious when they do. If they reach temperatures that are hot enough, synthetic materials don’t just burn — they melt directly to your skin.

That results in an injury much more severe and difficult to treat than a regular burn.

Obviously, you don’t want to experience any kind of burn injury. But, blazing hot material melting directly to your skin is certainly one to avoid.

The burn risk is so widely recognized that the National Fire Protection Agency (NFPA) forbids workers to wear meltable synthetic fabrics as the layer closest to their skin. But for some reason, this hasn’t been communicated very well to the average everyday worker.

Now that you know, take this precaution seriously. Avoid wearing synthetic clothing whenever there is a risk of fire or arc flash hazards.


The Dangers of Cotton Clothing Under FR Clothing

Now that you understand the risks associated with synthetic clothing, you might be wondering if cotton is a safer solution. While the NFPA and other safety regulations do allow cotton to be worn underneath FR clothing, it still isn’t the best option.

Unlike synthetics, cotton burns quickly. In the event of a fire or arc flash, cotton clothing can completely burn up within a matter of seconds. The good news is that it won’t melt to your skin like the synthetics will.

But, you can still develop burns and injuries from the cotton clothing.

The other hazard associated with cotton base layers is the added risk of both cold and heat-related illnesses. Have you ever experienced that sudden chill after working hard and heavily sweating?

As you sweat, the moisture can get trapped between your skin and the cotton clothing. So when you finally sit down and start to cool off, your body temperature cannot regulate properly. It can throw off your entire system. And, that’s when you take unnecessary chances with your immune system.

So what’s the solution?

Here’s one: Instead of wearing cotton as a base layer, choose a moisture-wicking FR garment that offers ultimate protection.


The Solution: Moisture-Wicking FR Garments


Moisture-wicking flame-resistant garments are made from a blend of materials that have been chemically-treated to achieve their flame-retardant properties. This base layer option is safe to use and is also quite comfortable. Many moisture-wicking FR garments are so comfortable that you can hardly tell the difference between them and synthetics.

Remember how we said that synthetic clothing such as nylon, polyester, and spandex should not be worn?

Some manufacturers develop these FR garments by using a blend of cotton and synthetics. Now don’t let that scare you. Because the blends are proportionate, the risk of having the garment melt is extremely low. The garments have been chemically-treated, too.

Other manufacturers have used modern technology to create a lightweight, moisture-wicking garment from inherently flame-resistant materials. Inherently flame-resistant clothing means the threads and fibers will naturally self-extinguish. Here’s one example from National Safety Apparel.

No matter what brand or clothing style you choose for your base layer option, make sure it offers flame-resistant protection. Stay away from non-FR clothing, even if you’re wearing flame-resistant layers on top. Burn injuries and fire-related hazards aren’t something you want to take a chance on.


Know what you need? Shop our flame-resistant clothing and apparel section directly by clicking here. Or, contact an RMI rep today for more information about FR clothing solutions that are best for your needs. If you need any advice, just ask. We’re here to help make it easy.