DRIVING SUITS

by Ken Myers

What is the risk of a fire inside a car during a race or in an accident situation? Fairly slim, I think we can all agree. Why, therefore, are fire-resistant driving suits required in NASA road racing? The risk may be low, but the results of a fire can be catastrophic indeed. Driving suits are another insurance policy we purchase to protect our most valuable possession, our life.

The driving suit is just one item used for total body protection. The other items include: helmet, head sock (balaclava), helmet skirt, head and neck support (such as a HANS device), helmet support (neck brace), gloves, underwear, socks, and shoes. All these items must work together to achieve total protection. If any one unit fails, it will undermine the effectiveness of the whole.

The driving suit is made of fire-resistant materials; yet not all suits are equal. Which is best, and what is good enough? The first question is easy, the second is a personal decision. There are five well-known materials on the market for fire protection: Proban, Carbon-X, Nomex, Kevlar, and PBI.

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. Therefore I do not recommend this material for the serious racer.

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 the same material used to make bullet-resistant vests for police use. This material is very tough and strong and also resists fire. But don’t try to stop any bullets in a driving suit! Bullet-proof vests are made of many layers of this material; and I’m sure they incorporate other trade secrets too. Perhaps you’ve seen TV ads for Kevlar leggings choking a chain saw. 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.

In a test in 1977, a state-of-the-art Nomex suit with two layers of Nomex underwear were worn into a ring of burning gasoline. This combination lasted less than 8 seconds! The person’s legs were severely burned. Considering this, is a single layer Nomex suit worth wearing? Can one get out of a burning car in less than 8 seconds, especially if it has just crashed? Are you willing to take that risk? If not, read further.

Obviously, the more material you wear or the more the material resists fire, the more time you will have to escape the source of the fire. A lesser known fact is that the air between layers of material is an equally important factor in insulating you from the heat of the fire.

Modern multi-layer driving suits are often made with a combination of materials to achieve the goals that the manufacturer is looking for. Those goals can be a combination of any of the following: Protection, Comfort, Style and Cost. Driving suits are rated in two different ways: the SFI rating and the Thermal Protective Performance, or TPP. The higher the SFI rating and the higher the TPP rating, the better. European made suits are also rated by the FIA.

NASA’s rules require a minimum of a 1-layer suit with underwear or a SFI 3.2A/5 rated suit without underwear. A SFI 3.2A/5 rated suit (usually referred to as a SFI-5 suit) will last a minimum of 9.5 seconds in a fire. When we talk about how long the suit will last, we are talking about the time it takes before you receive 2nd degree burns. Fire resistant underwear adds about 3 to 5 seconds of time.

In a non-scientific test, I put a Bic lighter flame directly on a single layer of Nomex material. The fabric charred, shrank, and burned through within seven seconds. Doubling the material layers resulted in the first layer doing the same thing but the second layer remained intact for over one minute. After charring, the first layer insulated the second layer from the heat source. However, the radiated heat through both layers would be unacceptably hot for this extended period. A second test proved this theory where a flame against the material against my hand was painful within 2 seconds with one layer and under 4 seconds with two layers.

Add to the driving suit a pair of Nomex socks, driving shoes made of leather or Nomex, Nomex gloves and a Snell SA-rated helmet and you have a complete fire-resistant outfit, right? This is all that the NASA requires. Well, what about the gap between the helmet and the suit? What if you have an open-face helmet?

Throw away the open face helmet or use it for autocrossing. For fire protection, you need a closed-face Snell SA-rated helmet and one or more of three other ways to prevent fire from burning your neck and chin. A fire resistant balaclava satisfies this requirement and so does a helmet skirt. These products are not uncomfortable and they do the job. Use one of these with a SFI-38.1 approved head and neck restraint. Most sanctioning bodies like NASA will soon require this addition to your safety equipment if they have not already done so. Another option is a donut-shaped neck support that will not only suppresses fire in this area, but it also gives its main benefit as protection from hyper-extension of the neck. In an accident, the head is forced to move in ways that it was never intended to move. Restricting travel by placing a foam shim between the shoulders and helmet can help prevent paralysis. (These devices have not been tested by the SFI to the 38.1 requirements and have not been proven in the same way to prevent neck injuries. Never use the foam neck collar at the same time as a SFI-38.1 head and neck restraint.) Although previously I used a foam neck collar, I now use the HANS device when I am racing.

Am I overly paranoid about fire? Maybe. I just feel that if you are going to do a job, don’t go half way. You bought your race car to blow away the competition. You take it to the race track to make the car perform up to its potential. This is serious business. Now, in the unlikely event that you crash and the gas leaks onto the hot exhaust, bursts into flames and you are left strapped in the mangled wreckage, are your insurance premiums up to date?

This series of educational articles is designed to help increase your performance and safety on the race track. Mr. Myers is the owner of I/O Port Racing Supplies and is a NASA Safety Tech Inspector.

Questions or comments can be directed to Ken Myers at 925-254-7223 or email to ken@IOPortRacing.com.