FR clothing is mostly concerned with Arc flash from electrical equipment and usually rated to take a certain amount of calories. This simply one method of measuring electrical energy. The Nation Fire Protection Agency (NFPA) sets the standards for FR clothing. All the standard says is that the clothing needs to reduce the amount of burns to the body by 50%. So that standard is very loose and doesn't really mean much, other then it will provide some protection and will not melt to the skin or make your burns worse.
But it does not quantify the reduction of burns.
SFI ratings do. You want to look for a suit with a SFI 3.2A rating tests a garment’s fire retardant capabilities. The last number on the 3.2A rating indicates how much time it takes before a 2nd degree burn is sustained.
3.2A/1 3 Seconds
3.2A/3 7 Seconds
3.2A/5 10 Seconds
3.2A/10 19 Seconds
3.2A/15 30 Seconds
3.2A/20 40 Seconds
The most common for racing are 1, 3, and 5.
These suits use Nomex for the material. There are 2 piece and 1 piece suits available at many different price points. There are various designs that can use 1, 2, or 3 layers. Typically 2+ layers are thinner, lighter, and breathe better. But the ratings may be the same between suits.
Be aware of Karting suits as well, they are cheaper and carry a SFI 40.0/1 rating but it's not a fire Resistance, they are rated for abrasion and typically made of Nylon. Nylon melts and burns very quickly does not provide any fire protection.
There are several types of material used for Fire Suits; Proban, Nomex, CarbonX, Kevlar, and PBI.
Here is the run down on those from the NASA racing site.
Best way to prevent burns is by using layers. The reason for this is that each layer will have a layer of air between them. Air is an excellent insulator of heat so the more air layers you have the longer it will take to create a burn.Proban is a treated cotton fabric and comes in a variety of colors. Proban is used in low-cost products and is good for someone that will not be in the sport long or will be replacing the suit often. The treatment does not wash out, but like cotton jeans, the material gets thinner with washing.
Nomex is the most known and used material in driving suits. Nomex is available in both woven and knit fabrics and a variety of colors. This is not true for Carbon-X, Kevlar and PBI. If you want style, Nomex is the only way to go. However, if you want protection with an added benefit of comfort, Carbon-X, Kevlar and PBI should be considered.
Carbon-X is relatively new on the market and is a pre-burned (oxidized) polyacrylonitrile fiber. This material has excellent fire resistant properties but at this time is limited to black color only. It can be difficult to work with in the manufacture of clothing. This material is used in suits, balaclavas and underwear.
Kevlar is very tough and strong and also resists fire. Kevlar is expensive and hard to work with so it is used mainly in premium driving suits.
PBI will not melt or burn in the air and is as comfortable as cotton to wear. Nomex, on the other hand, will melt, become brittle and lose its strength rapidly. PBI, however, has a problem with stretching so it is not used often in driving suits.
Here is some more information from Military testing:
The DCU fabric mentioned above is similar the the Proban type material. Note the 3-10 seconds of escape time.Conclusions
The DCU is made of a cotton/polyester blended fabric. In all comparative flammability
studies, this type of fabric experienced thermal failure, resulting in burns, well before any
Nomex fabric used in similarly constructed garments.
Nomex fabric is much more durable than the DCU fabric. Nomex outlasted cotton by a factor of at least four to one in all wash cycle and wearability tests.
Nomex uniforms will provide better protection than the DCU during exploding FFE
attacks because it will resist more intense heat and last far longer. Nomex provides the best combination of flame resistance, insulation, comfort, durability, versatility, and cost-effectiveness.
In accordance with the study Fire Test of Advanced Aramid Blends and Treatments,
Nomex BDU uniforms will shrink less during fire events than Nomex flight suit
Procedures to ensure that Nomex garments perform up to their potential:
1. Wear natural fiber undergarments such as cotton or wool. FR undergarments provide
even better protection. Common synthetic fabric undergarments containing a blend of
nylon, polyester, or polypropylene will melt at relatively low temperatures and severely
burn individuals who are escaping fire emergencies.
2. Wear layers. Air is an excellent insulator. Air between layers of clothing greatly delays
the transmission of heat and plays a major role in insulating the wearer's skin from the
heat of any impinging flames.
3. Use only garments, which meet MILSPECS. Some inexpensive garments sold as FRrated
have been found to be constructed with flammable dyes and threads, which melt in
the presence of elevated temperatures. Fasteners, such as zippers and buttons must
withstand temperatures on par with the garment's fabric in order to prevent premature
4. Be wary of contaminants. Most insect repellants, petroleum products, and even body
oils degrade the ability of FR garments to withstand flames and high temperatures. Wash
garments in accordance with label instructions.
5. Limit exposure times to extremely high temperatures when possible. Nomex uniforms
are flame resistant, not flame proof. All military FR garments are designed to provide a
few SECONDS (normally 3 to 10 seconds) of escape time during fire emergencies before
thermal injuries occur. All garments of all types will eventually fail during a large and
Another study using the PBI fiber found this:
These guys have alot of used race suits for sale. Looks like alot of Nascar suits, etc.Use of cotton and fire retardant treated cotton flight suits resulted in an average of greater than 60 percent body area burned. Nomex coveralls resulted in greater than 30 percent average body area burned. Polybenzimidazole (PBI), an experimental fiber developed by the Air Force Materials Laboratory, resulted on the average, less than ten percent body area being burned.