In-Car Fire Suppression Systems

NASCAR has made significant advances in protecting drivers from crashes, but fire is more of a challenge. Let’s take a look at how fire suppression systems have evolved.

Ryan Blaney on Fire, 2018 Coca Cola 600

A Brief History of Fire Suppression Systems

A loaded NASCAR racecar carries 20 gallons of fuel and more than a gallon of oil. All those combustible materials are in close proximity to hot metal and electrical equipment being pushed to their limits. A broken part can rupture a fuel or oil line, spreading flammable liquid everywhere.

Fireball1 Roberts’ death after a fiery wreck2 in the 1964 World 600 spawned NASCAR’s first fire safety rules.

  • NASCAR mandated fire-resistant driver safety gear. Drivers used to dip street clothes in fire-retardant chemicals. Roberts was an asthmatic and the chemicals used worsened his symptom, so he didn’t use the chemicals.
  • Every car had to have an on-board fire-extinguishers within reach of the driver
  • Rubber fuel cells replaced steel fuel tanks, which could easily rupture in a crash.

But That Wasn’t Enough

The driver’s best protection against fire is getting out of the car; however, that’s not always possible. NASCAR firesuits protect against second degree burns for about 10 seconds. If a car bursts into flame at 200 mph, it could take more than ten seconds for the driver to stop the car much less get out of it.

A crash may also impair the driver’s ability to steer or get out of the car. In Dale Earnhardt, Jr.’s 2014 Texas crash, the car stopped with the driver’s side jammed up against the outside wall. Dale had to wriggle out of the car and walk across the car’s hood to get away from the vehicle.

Ironically, many of the safety improvements for impact make it harder for the driver to get out of the car quickly. Things like wrap-around seats, HANS devices, helmets and gloves complicate driver egress.

Do-It-Yourself Fire Suppression

The first on-board fire suppression systems were portable extinguishers. In case of fire, the driver had to locate the extinguisher, aim it and pull the pin. Then the car filled with powder in addition to the smoke. The chemical powder used to smother the fire was extremely hard on human lungs.

The final weakness of this system is that it didn’t address the worst case: a driver unable to get himself out of the car.

The Indianapolis Star story about AJ Foyt starting a trend with in-car fire extinguishing systems

Taking It Out of the Drivers’ Hands

A.J. Foyt’s team debuted the first automatic onboard fire extinguishing system debuted in the 1967 Indy 500. After Foyt had a fiery crash in Milwaukee in  1965, DuPont representatives offered help designing an integral fire extinguisher system.

Foyt’s team added a temperate-sensitive switch that would automatically deploy in case of fire. (In 1975, Indy 500 competitors accused Foyt of hiding extra fuel in his fire extinguisher.)

Defining the Problem: It’s Not Just Fire

The driver’s cockpit has a volume of about 100 cubic feet. NASCAR requires a 5-lb manually-activated fire extinguisher in the driver’s compartment. The drawing below shows the locations of the nozzle and the switch.

A graphic showing the NASCAR in-car fire suppression system

When Ryan Blaney’s crew chief asked if he had activated the fire suppression system, Blaney’s response was:

“Dude, I was trying to get out of it. I didn’t look for the pin. I couldn’t see it regardless. –Ryan Blaney”

In 2003, NASCAR required a separate, thermally activated fire extinguisher system for the fuel-cell area. This system contains 10 pounds of extinguishing chemical for the 17 cubic foot fuel cell compartment.

The Fire Triangle shows the elements needed for a fire: Heat, Fuel and Oxygen

Putting Out Fires

Fire requires heat, oxygen and fuel. Once you have these three components, fire continues via a chain reaction.

Heated fuel produces gas-phase free radicals — highly reactive compounds that quickly combine with oxygen from the air. That combustion reaction produces more heat. That heat frees more free radicals from the fuel, which combine with oxygen and produce more heat. It’s like a nuclear chair reaction, but at the molecular level.

You must eliminate (or more) one of the components in the chain reaction to break the chain.

How Water Puts Out Fire

Water cools a fire, eliminating the ‘heat’ component. Heat turns water from liquid to steam. Water redirects the fire’s heat into vaporizing the water, so there’s less heat available to form more free radicals.

Also, a thin layer of water forms between the fuel and the air around the fuel. That layer separates the fire and the fuel, making it harder to sustain the chain reaction.

Gasoline Fires

Water extinguishes fires involving Class A Combustibles like paper, wood, and clothing. Grease and oil (Class B combustibles) don’t respond to water.

  • Firstly, water cannot form a protective barrier between fuel and air because the fuel floats to the top of the water
  • A stream of water can cause fuel to spatter, which distributes the fuel over a wider area.

Carbon Dioxide Fire Extinguishers

One way to suppress a gasoline fire is with chemicals that smother the fire by removing or displacing oxygen. Carbon dioxide (aka CO2), is heavier than air, so it works the same way water works on Type A combustibles displaces the air around the fuel. The foam covers the fuel and forms a barrier against oxygen. A pressurized liquid also comes out cold, adding heat mitigation.

The major problem with CO2 extinguishers for race cars is that drivers need oxygen, so removing the oxygen causes a problem. Never use carbon dioxide extinguishers in confined spaces.

Dry Chemical Fire Suppressors

Chemicals like monoammonium phosphate (also used as fertilizer), sodium bicarbonate (yes, baking soda) and potassium bicarbonate also create a barrier between oxygen and fuel.

The risks of dry chemicals outweigh the benefits in motorsports because an explosion of powder could keep the driver from seeing (or breathing). They’re also really hard to clean up.

Halon

A.J. Foyt’s 1967 system used Halon 1301 (CBrF3). Halon is a chlorofluorocarbon gas. When pressurized, a lot of halon fits in a small container. When deployed, the gas expands to covers the entire volume, providing protection that doesn’t requiring any aiming.

Halons were first used in World War 2 on aircraft and tanks (which are always good comparators for racecars). They didn’t impair the driver’s vision and, because Halon doesn’t form conductive ions, it doesn’t damage electronics.

Unfortunately, the heat in the racecar during races warmed the Halon 1311 gas and the cylinders discharged without warning. A variant (Halon 1211) was preferable because it didn’t need to be held at such high pressure, so it didn’t discharge accidentally.

The Halon 1211 molecule

Halon 1211 is the brand name for bromochlorodifluoromethane , or CF2ClBr. The rule requiring 5 lbs of of an approved extinguishing gas in the cockpit comes from testing on this compound.

Halon does cool the fuel, but its primary fire suppression mechanism is attaching to the free radicals before the free radicals can combust with oxygen. This breaks up the chain reaction.

Halon breaks the chain reaction of fire by stopping free radicals

Because Halon doesn’t displace oxygen, it works well in confined spaces. It’s stable and easily recyclable. It was the fire suppressant of choice until we realized how badly chlorofluorocarbons damage the ozone layer. (Another name for Halon is Freon 12B1.) The Montreal Protocol banned CFC production in 1994.

Today’s Fire Suppressors

The need for an alternative to Halon wasn’t just a motorsports problem. Halons were the global industry standard for fire protection. DuPont took the lead to find alternatives. As with any critical application, you end up with a long list of requirements.

  • Effective at suppressing fire
  • Acceptable human inhalation toxicity
  • Does not impair or obstruct the driver or rescue team
  • Ability to suppress a fire shielded behind something
  • Easy to use
  • Easy to clean up
  • No residue that would affect subsequent track grip
  • Electrically nonconductive
  • Small and light
  • Shelf stable

FE-36

DuPont’s FE-36 is a hydrofluorocarbon: 1,1,1,3,3,3-Hexafluoropropane or CF3CH2CF3. Hydrofluorocarbons are similar to chlorofluorocarbons, but since hydrofluorocarbons have neither bromine nor chlorine atoms, they are not damaging to the ozone layer.

They aren’t quite as effective as the Halons, but they do the job and don’t have the cardiac sensitization issues of the chlorofluorocarbons. FE-36 quickly became the prime ingredient in motorsports fire suppression systems.

But…

Although they don’t attack the ozone layer, hydrofluorocarbons are still greenhouse gases. FE-36 has an atmospheric lifetime of 220 years. That means that if a FE-36 fire protection unit goes off during a race, those FE-36 molecules will be hanging around our atmosphere until 2238. A similar chemical, FM-200 is a little better because its atmospheric lifetime is only 33 years, but that’s still a pretty long time.

Because of these concerns, legislation to regulate and eventually phase-out the use of these chemicals is being considered (mostly in the European Union at present).  Chemical manufacturers have gone back to the drawing board.

The Novec 1230 molecule

NOVEC 1230

In 2012, Greg Biffle’s #16 car debuted a NOVEC-1230 fire suppression system created by 3M, then Biffle’s sponsor. “NOVEC” is the trade name for CF3CF2C(O)CF(CF3)2 – aka dodecafluoro-2-methylpentane-3-one.

Novec 1230 absorbs heat, just like water. The mechanism is a little more complicated. Novec 1230 combines with air to form a gas capable of absorbing a lot of heat. It also evaporates 50 times faster than water.

Novec 1230 offers similar no-ozone-depletion, but creates much less of a greenhouse gas load. The positive is that Novec 1230’s atmospheric lifetime is only five days. Novec 1230 shows a lot of promise for the biggest fire-suppression issue these days: protecting data centers where huge numbers of hot-running servers store people’s critical data.

No Solution is Perfect

A series of pit-road accidents lead F1 to prohibit cars from refueling during races in 2010. While it adds an interesting strategic element (the car’s handling changes greatly as the fuel load goes from 100 pounds toward zero), I don’t see it happening in NASCAR.

As we’ve said here before: There is no way to make racing entirely safe.

Notes

  1. Fireball Roberts got his nickname from his baseball career, not as a result of the accident that ultimately led to his death.
  2. Roberts emerged from the crash with burns over 80% of his body and miraculously survived for several weeks, but ultimately contracted pneumonia and sepsis.

Note: This post was revised and updated on May 6, 2020 from the original.


Also published on Medium.

3 Comments

  1. “There is no way to eliminate the possibility of fire in motorsports.” Never has a truer word been spoken.

    If we enjoy motorsport, we have to accept that there are risks, just like anything in life. And given the speeds achieved, it’s actually amazing how little incidents there are, really.

  2. Ugh. As someone who worked around datacenters, HALON systems and their successors are just as bad, if not worse, at displacing oxygen as CO2. I’d personally rather have a CO2 system, as it’s guaranteed to be non-toxic, and it’s a normal atmospheric compound. You may not be able to stop within 10 seconds, but you can generally deal with holding your breath for more than 30 seconds.
    (2nd post due to SSL failure)

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