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
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
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 dont try to stop any bullets in a driving
suit! Bullet-proof vests are made of many layers of this
material; and Im sure they incorporate other trade secrets too.
Perhaps youve 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
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 persons 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.
NASAs 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
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, dont 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
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
Questions or comments can be directed to Ken Myers at
925-254-7223 or email to ken@IOPortRacing.com.