What To Wear Under a Hazmat Suit

A hazmat suit is designed to cover all or the majority of your body while you work. Your PPE may include a self-contained breathing apparatus, rubber gloves, booties, helmet with face shield and anti-contamination suit. With all these components layered over your body, it is important to wear the right clothing under your hazmat suit that will keep you functioning and comfortable at all times.

What Should Hazmat Suit Undergarments Do?

Undergarments for a hazmat suit should:

Not interfere with the function of the suit and accessories

Wick away moisture
Protect you from chafing
Keep you cool or warm

Resist odor build up
Prevent bacteria formation
Not react with the chemical agents

Protect you from fire

*Image: Nomex fireproof hazmat undergarments courtesy of DuPont*

If you’re in the market to buy a hazmat suit and have specific questions the we suggest checking out our Essential Hazmat Suit Buying Guide here >

Proper Fit

The your hazmat suit undergarments should fit you snugly, but not too tight.

If the hazmat suit is air-tight, like a chemical suit, you should wear close-fitting underwear. Tightly fitting full-body undergarments have the least chance of interfering with your motions.

Be sure that your base layer does not interfere with the seal around the hazmat suit.

If the outer surface of the undergarments are smooth, this will prevent chafing by allowing the protective suit to slide over them easily. Tight undergarments facilitate getting the suit on and off, and helping mobility by not grabbing the suit as you move around. Make sure you can lift up your arms without any of the hazmat suit bunching up around your waist. The hazmat suit should not restrict movement in the trunk area.

Hazmat Suits that are not air-tight do not require skin-tight clothing. Looser-fitting upper and lower body layers are generally acceptable.

In colder environments, you may need to wear thicker garments or multiple insulating layers under your hazmat suit. In that case, make sure the hazmat suit is large enough to accommodate additional clothing.

Moisture Wicking

With hazmat suits that are air-tight and sealed from chemicals or liquids, heat inside the suit is normally the main problem. Sealed hazmat suits will trap your body heat and moisture, causing chafing and discomfort if it’s worn against the skin for extended periods of time.

Moisture-wicking is very important when wearing a sealed hazmat suit with a clear hood covering your head and shoulders. If moisture reaches the inner suit layer, it will fog up the hood, severely limiting your visibility. This will curtail your work time and could be dangerous.

Moisture-wicking textiles include:

Synthetic fibers – Capilene, Polartec, polypropylene, polyester

Merino wool

Moisture-wicking long underwear textiles worn against the skin help prevent chafing and rashes caused by sweat and its evaporation. This makes moisture wicking long underwear good for wearing under a hazmat suit.

When donning base layers under a hazmat suit you don’t want to feel too warm right after you put everything on. As you begin to work and move around, your body temperature and the interior of the suit will heat up. If you feel comfortable at rest, you are probably overdressed and may overheat once you start working.

Fire Proof and Chemical Proof

The clothing worn under a hazmat suit should also be non-flammable and non-reactive to the types of chemicals you’re dealing with.

For aluminized hazmat suits used in firefighting you should wear full body fireproof nomex pants, jacket, gloves and hood. Nomex is inherently flame-resistant and will not melt, drip or contribute to combustion. According to DuPont Nomex is NFPA 1975 compliant, is lightweight, can be washed 125 timesk and reduces the propensity for skin burns by 50% or more compared to cotton.

For chemical suits used for flammable and/or reactive compounds, you generally need flash fire protection and inert (non-reactive) chemical behavior. Chemical-protective underwear (CPU) made from an activated carbon-based textile should be worn under the hazmat suit as a secondary protective measure. The underwear protects you if your outer fully-encapsulated or non-encapsulated hazmat suit fails or is circumvented. Activated carbon textiles are breatheable, flexible and can be washed. They have a low permeation rate as the activated carbon absorbs the chemical agent. Examples include:

Polymerically encapsulated carbon integrated with Nylon/Lycra tricot fabric (developed by U.S. special forces)
Charcoal-containing cotton flannel, coated on one side with fluorochemicals and the opposite side with active charcoal-polyacrylate emulsion (developed for the Chinese army)

If you’re working in a cold environment and need additional insulation, then you can wear a military-grade lightweight chemical-biological suit under your hazmat suit. These use active-carbon sphere protective textiles. Examples include:

Joint Service Lightweight Integrated Suit Technology (JSLIST)
UK Mark IV NBC
French NRBC Protective Suit

Source: Advances and Applications of Chemical Protective Clothing System, Journal of Industrial Textiles

Odor Resistance

If you spend a lot of time in a hazmat suit, your undergarments will quickly absorb sweat and odors from your body. Fireproof and chemical-resistant undergarments are not cheap and have a limited life if you wash them often. Odor resistance is therefore a very useful feature.

Most synthetic materials such as Capilene, Polartec and various polypropylene and polyester versions have natural odor resistance. Some manufacturers add special odor-resistant capabilities to their materials. This additional feature is a good investment.

Bacteria Resistance

Finally, hazmat suit undergarments with resistance to human and external bacteria growth can increase your overall safety. Bacteria growth resistance is primarily designed for the wearer’s own bacteria, or bacteria that grows in moist environments. However, this can also add some protection against external bacteria from the suit, storage or working environment. Bacteria resistance typcially goes hand in hand with odor resistance.