A fire is one of the most frightening possibilities faced by racing drivers and even casual track day wonders. It can be fueled by anything from the plastic in your dash or insulation on your wires or subsystem fluids like oil, power steering, or braking. Flames are made unthinkably worse by an accelerant such as a fuel leak or ruptured fuel cell, and compounded by the possibility of oxidizers like nitrous oxide. Understanding the possible scenarios and preventative courses of action will help minimize the potential for injury.
Fire suppression systems are designed to save the occupant first and the car second, providing occupants with more time to escape the confines of the car. Selecting the right system for your priorities requires examining a few different schools of thought. Nozzle placement, extinguishers formula, and mounting all need special consideration and planning.
Types Of Extinguisher Charges
Pretty much all racing organizations require at least one onboard ABC fire extinguisher — usually mounted on the floor, behind the seat, or on a roll cage tube. These small handheld extinguishers are for general use and do not offer deployment options beyond the standard pull the pin, aim, and sweep method.
ABC fire extinguishers use a dry powder media called mono ammonium phosphate that is charged with carbon dioxide. This blend of fire retardants acts to smother flames by depriving them of oxygen and insulating hot surfaces in a powdery mess. ABC refers to the general-purpose nature of the media:
A-rated: Extinguishers are meant to handle general fuels fires such as wood, paper, cardboard etc.
B-rated: Designed for liquids like gasoline, oil, alcohol
C-rated: Meant for electrical fires. While these different types can be had separately, it is most common to find them lumped together.
The advantages of the ABC include commonality — they can be bought at any hardware store in a variety of sizes at a reasonable price, usage — simple to use and mount, and effectiveness — for small to moderate fires the ABC gets the job done without fear of exacerbating a fire because an inappropriate method was used to attempt to extinguish it.
The first, and most widely known of the true high-performance gaseous fire suppressants, is halon. According to Encyclopedia Britannica, “The effectiveness of halons in extinguishing fires arises from their action in interrupting chain reactions that propagate the combustion process. Halons are nonconductors of electricity and can be used in fighting fires in flammable liquids and most solid combustible materials, including those in electrical equipment.”
Halon fire extinguishers are prevalent in aviation applications like jet engines and airframes for multiple reasons. First, it is known to put out fires fast! Secondly, is the preservation of systems and materials it comes in contact with. Encyclopedia Britannica further articulates that, “Halon 1301 (bromotrifluoromethane) is especially favored for extinguishing fires involving electronic equipment because it leaves no residue and does not cause electrical short circuits or damaging corrosion of the equipment.”
Contained as a liquid under pressure, halon is sprayed onto the fire and evaporates quickly into a gas that continues to displace oxidizing air and interrupt combustion. Halon was the fire suppressant of choice among racers until environmental concerns limited its wide spread usage to very rare instances.
After halon was effectively banned by the EPA, “In 1994, halon production ceased in development countries after scientific evidence suggested that halon contributes to the depletion of the stratospheric ozone layer,” detailed Robin Bennett of Boeing.
In his article Replacing Halon In Fire Protection Systems: A Progress Report Bennett explores the lead up to what resulted in the ban of halon, and the attempts to find suitable alternatives. His findings reveal that while comparable products exist in the market they do not compare in the size and weight advantages halon offered.
Among the common alternatives widely found today is a DuPont product called FE-36. Championed by aftermarket fire suppression system maker Fire Bottle, it offers impressive effectiveness and options for motorsports applications. See how FE-36 works instantly here:
FE-36 is packaged just like halon and works similarly According to DuPont, “FE-36 has comparable performance and efficiency to halon 1211, lower toxicity, as well as zero ozone depletion potential. DuPont FE-36 is safe for people, a clean agent that does not leave a residue, electrically nonconductive, noncorrosive and no thermal shock.”
We talked to Donny Skaggs of Fire Bottle about FE-36 and the options modern racers have to add another layer of protection to themselves. “The FE-36 is really good, it’s kind of a sister chemical to halon, it’s just a little more environmentally friendly. It takes five times more oxygen for a fire to live than a human being, you wouldn’t want to get in a closet and set one off but there’s enough air exchange in racing that we’ve never had a problem.”
Last in the options for fire suppression is aqueous fire fighting foam (AFFF). This solution is commonly used on flight lines and aircraft carriers to extinguish and cool raging fires resulting from aviation accidents. The water-based mixture looks like shaving cream and erupts onto the scene like fire retardant whipped cream.
AFFF extinguishers often include an external propellant in the form of a carbon dioxide cartridge.
The debate between gaseous fire extinguishers like halon and FE-36 and foams like AFFF rages on as fire science and real world applications make cases for each. Halon and FE-36 are known to extinguish flames virtually instantly, but they are fleeting and dissipate quickly after the discharge ends. At this point there may be remaining hot surfaces, fuels, and oxidizers to re-ignite the fire.
AFFF on the other hand may not extinguish the flames as quickly or completely, however the cooling and residual effect will keep the flames out. This lasting effect comes at the cost of potential future corrosion and electrical shorts. A good argument for AFFF is made by 949 Racing here:
Nozzle And Cylinder Mounting
Fire suppression kits whether they be halon, FE-36, or AFFF, are generally composed of several parts — a charged and certified bottle complete with an SFI date punchcard, two to three nozzles, a length of flexible hardline, and a pull T-handle. It is left to the car builder to tailor the mounting of their new system, here are a few tips.
Photo source: Fire Bottle
It is important to disconnect your sentimental attachment to your car here, and consider your health and safety. “This is designed to save the driver, not the car. I recommend putting both nozzles on yourself,” reminds Skaggs.
That being said, most kits come with multiple nozzles and can still be distributed to help limit the spread of fire, and possibly stop it at some of the most likely sources.
“What I recommend is — the five-pound kit comes with two nozzles, and the 10-pound comes with three. As long as you get one nozzle centrally located towards their body, I’m ok with that. They have a 25-second discharge time and it will fog their ass out of there! I don’t want them to put one on the motor and one in the fuel cell area and nothing on them. A lot of guys will get a 10-pound bottle and that way they can cover under the hood, one on the driver and one on the fuel cell, which is great,” Skaggs elaborated.
Placing a nozzle at the fuel rail or carburetor in the engine bay, and at the pick-up/fill tube of the fuel cell covers the lost common sources of a fire. Of course fires can be generated from the brakes, electrical systems or other areas, one involving fuel is sure to be the most severe.
Placing nozzles in the engine bay to cover both the hot exhaust side and the cool fuel rail side of the engine can help extinguish a fire.
Makes sure you prioritize the safety of the occupants over the car, point at least one nozzle directly at each occupant to give them the best coverage and the most time to escape the fire. Common locations for a centrally-mounted nozzle include between the helmets rising above the shoulder harness bar, or in the dash facing back.
Pull handles accessible to both vehicle occupants and course workers help increase the chances of a successful system deployment. Below, multiple interior nozzles to protect the driver.
When it comes to mounting the actual fire extinguisher cylinder take care to put it somewhere protected and secure, as nothing is worse than having a loose article in the cab of the fast moving car, especially when that object is metal and under pressure. Check out the video below to see the potential inconvenience and hazard of a loose extinguisher.
“The bottle can lay down or stand up and has a flexible dip tube so it will work in any position. Most guys lay them down,” explained Skaggs. So in the event of a roll over or other strange attitude the contents of the fire extinguisher will still dump when the cable is pulled.
Multiple bottle mounting orientations are acceptable due to the internal flop tube. Photos source: Fire Bottle
A fire suppression system buys peace of mind, and having less things to be worried about when prepping and racing your car, the more energy you can focus on the task at hand. Those who start their children young in motorsports live with a unique kind of pride and terror. It is fantastic to share your passion for racing with your children, and support their efforts, but the same risks accepted by adults exist.
Fire Bottle’s AMRC500 system includes a thermostat to activate the system at temperatures above 170 degrees F.
“I’ve got a new bottle that I introduced recently, it’s called the AMRC500. It is cable activated like all of them and I put them in cars driven by young kids. If something happens and they can’t hollar ‘dad’ over the radio because they have a fire there is a nozzle that comes out of the bottle and is centrally located in the car — if they pass out or panic it goes off at 170 degrees F. If they want to set it off manually they can do that too, but if they can’t see their T-handle it dumps automatically,” Skaggs said.
The standard aluminum hardline makes for easy plumbing, but can be prone to cracking over time.
One concern that stems from personal experience is the nature of hardline plumbing and the high-vibration environment of a race car. Aluminum flexible tubing is cheap and makes for easy plumbing of nozzles throughout the car, but may be prone to cracking and breakage if it is located in a high-traffic area.
To combat this issue flexible, braided lines much like stainless brake lines can be used in place of the aluminum. While this adds expense and complication to the system, it also provides reliability. There are not t0o many things worse than pulling that cable in a fire and having nothing happen.
Consider a fire system for your race car, even at the slowest and cheapest forms of motorsport it is a wise investment. Install your nozzles with an eye toward occupant safety, don’t worry about the car. Lastly, make the inspection of your system a regular part of your pre-race checks. Look for cracks in the lines, check the cylinder certification and pressure, make sure the cylinder is mounted securely, and remember to remove the safety pin to arm the pull cable.