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Fire Fight

The ins and outs of fire extinguishers for your car.

By Michael Knowling

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This article was first published in 2000.
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Let's face it, we car enthusiasts who like to fiddle around with our cars are far more likely to fall victim to a car fire than the average Joe. Whether we're fiddling around with something electrical, fitting a new fuel system or hitting a nitrous button, we're running a much higher risk of sparking a potentially destructive fire. And all that hard work (and those hard-earned dollars) can be flushed down the toilet in one fast and final blaze of glory.

But there is one way to cover our butts if a fire ever does erupt in our car - in-car fire extinguishers. These have been around in some form for donkey's years now, but there's now a great range to chose from - right from a K-Mart general purpose cheapie all the way up to a full-blown FIA spec plumbed in-car extinguisher system.

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Firstly, there are three methods to kill a fire - remove the air by smothering, remove the fuel, or alternatively, remove the heat by cooling the burning fuel. This can be seen in the above triangle - remove any one aspect and the triangle falls and the fire will go out. Fire extinguishers endeavor to eliminate one or two of these necessary components.

Car fire extinguishers can be divided into two groups - handheld and integrated in-car.

Handheld Extinguishers...

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This is the most common type of extinguisher to be used in road car applications - and they're a good general purpose extinguisher too: perfect for when that family BBQ goes horribly wrong!

Some common sizes are 1.5, 2.5, 4 and 5kg and most come complete with a mounting bracket and retaining strip included in the package. Obviously, it's important to mount a handheld extinguisher in a place of easy access - and somewhere where the fire itself is not likely to erupt. Make sure when you're buying that a strong retaining bracket is provided - you don't want the extinguisher to become a missile in a crash.

As an example of one of the better handhelds, this Safecraft extinguisher is precision machined from billet aluminium, has a quick release bracket, stainless steel internal parts, contains the proven Halon 1211 gas in either 2 or 3 pound capacity and is fully rechargeable. Options are a high polish finish, colour fusion coat, billet machined mounting bracket and a water based RACESAFE F-500 extinguishing agent.

How to use a Handheld Extinguisher

If you've just gone out and bought an extinguisher, it's pretty bloody important to make sure you know how to use it in an emergency. Here's an easy to remember acronym for how to operate a handheld fire extinguisher:

PASS = Pull, Aim, Squeeze, Sweep

Pull the pin at the top of the extinguisher that usually prevents the handle from being accidentally pressed. Aim the nozzle at the base of the fire for maximum extinguishing effectiveness.

Stand around 2 metres from the fire and Squeeze the handle to discharge the extinguisher.

Sweep the nozzle back and forth over the base of the fire.

Then, after the fire appears to be extinguished, watch it carefully as there is a chance it may re-ignite. Note that the approximate discharge time for a smaller handheld dry chemical extinguisher is likely to be around 10 seconds or less.

Integrated In-Car Extinguishers...

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This type of extinguisher is most commonly found in competition motorsport vehicles, but it is also suitable for disabled persons who might not be able to operate a hand-held unit. These systems work in a variety of ways, but most commonly there's a network of tubes under the bonnet, which, in the event of a fire, break to release the fire retardant. These retardants include gases (such as Halon 1211 and PCF-410), dry powder and foam (known as AFFF). Note, however, both dry powder and foam types are messy to clean up after use. The SPA Design Firefighter is a semi-automatic extinguisher. In this system, the driver needs to activate a button or lever to release the foam retardant under the bonnet.

The Safecraft Racesafe system features a universal 5-way billet aluminium operating head, flexible method of activation, high pressure DOT rated cylinders in 5, 10 and 20 pound capacities There are also three outlet ports to attend to different parts of the car. Some options include a polished cylinder and electronic actuators and switches.

Extinguisher Suitability...

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Be warned! Not all extinguishers can be used on any given fire. There are now six official categories of fire - Class A, B, C, D, E and F.

Class A is for normal combustibles, such as paper, fabric and clothing. To extinguish this type of fire, simply remove heat by cooling the temperature of the burning material below combustion point. Water, C02, BCF or AB(E) dry chemical extinguishers are best in this situation.

Class B fires occur in flammable liquids like petrol, oil, spirits and many other liquid chemicals. These are extinguished by removing air from the fire through placing a blanket of foam over the material. Either that or by BCF, C02 or dry chemical extinguisher.

Class C is now classed as a flammable gas fire - not an electrical fire as previously. These fires should not be extinguished unless the gas source can be turned off and the cylinder kept cool with a water spray.

Class D fires are classed as combustible metals such as magnesium and sodium. Note that only a dedicated combustible metal extinguisher should be used in this case.

Class E is an energised electrical fire. When attempting to put out this type of fire, only extinguishers that are non-conductive can be used (ie not water or foam type extinguishers). Foam extinguishers must not be used either. Use BCF, dry chemical or CO2 extinguishers.

Class F fires involve cooking oils and fats. The best extinguishers for a Class F fire are B(E) dry chemical and wet chemical.

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With all of these classes of fire, it makes sense that various extinguishers are made suitable for multiple applications. Some are more flexible than others - but here's the some of the most common types of extinguishers available:

BCF (Vapourising Liquid) extinguishers contain halongenated hydrocarbon. They are suitable for many types of fire have a good range and leave no residue. In Australia these extinguishers (easily identified because they are bright yellow) are now illegal.

Dry Chemical extinguishers are a good all-round choice and are usually rated for multiple purpose use. They contain a special extinguishing agent and use a compressed, non-flammable gas as the propellant. A blanket of non-flammable material is left on the extinguished material to reduce the chance of re-ignition - but they do leave a big mess!

Water These extinguishers contain only water and compressed gas and should only be used on Class A fires.

Carbon Dioxide (CO2) extinguishers are identifiable by their large outlet horn and are very suitable for electrical fires and on small flammable fires. Also, since the gas disperses quickly, these extinguishers are only effective from 3 to 8 feet. No residue is left.

Extinguisher Number Ratings

Both Class A and Class B extinguishers have a numerical rating to determine the extinguishing potential for each size and type of extinguisher. On Class A extinguishers, the number refers to the volume of water it holds and the amount of fire it will extinguish. On Class B extinguishers, it indicates the approximate number of square feet of a flammable liquid fire that a non-expert person can expect to extinguish. Simple - the higher the number, the better.

Extinguisher Service and Maintenance...

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An extinguisher is definitely not a maintenance-free bit of gear. They should regularly be inspected at intervals recommended by the manufacturer. For example, most handheld extinguishers should be serviced within every 5 years and any type extinguisher should be recharged within every three years. Regular inspections should be made for cracks, content loss and (if applicable) gauge pressure. Cracked or broken hoses should be replaced and nozzles must be kept free of any obstructions. If you've got a handheld dry chemical fire extinguisher, periodically turn it upside down and shake it to prevent the filling packing at the bottom, which could render it useless.

Oh, and never just "try it out" to see if it works. Once activated, gradual discharge will occur - so you need to have it recharged at the first opportunity.

Automotive Fire Fighting Dangers...

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There are some more specific dangers when dealing with auto fires. These are things such as exploding gas struts, tyres, fuel tanks and even small airbag igniters. Viton rubber parts (often used for seals, grommets etc) are also a danger, as they behave like a strong acid once they touch your skin.

So please, if you're ever in that horrible position - be extra careful!

Smoke then Flames

The old Holden was pulled off the side of the road, bonnet lifted, doors open and smoke billowing from every orifice. The hysterical young women - moments before driving down the road - were clutching each other; supported only by the chainwire fence they were leaning against. I saw all of this in moments, pulling my Alfasud off onto the shoulder behind the smoking car as I reached down for the small handheld extinguisher permanently mounted in the cabin. Another driver had also stopped to assist, and it was he who identified the fire source as being under the dash. He yanked the door open wider and I fired the extinguisher in the general direction of the flames, the powder-type cylinder emptying in seconds. It made no apparent difference.

The road passed through an industrial estate and I quickly sought and received another - much larger - extinguisher from a nearby factory. This one took a lot longer to empty, making a hollow 'baaaarf' sound every time I pulled the trigger. The flames - probably fed by oil-soaked underfelt - kept on flickering, the smoke pungent. At this stage a fire engine - summoned by the factory personnel who had leant me their extinguisher - pulled up, siren dying to nothing. As far as I could see, the firemen didn't worry about fancy extinguishers - they just drenched the car with water, and the flames went out in seconds.

That incident occurred nearly fifteen years ago and I remember it vividly for one reason - small car-type fire extinguishers give you only one, brief, chance to get those flames out. If you can't see the actual fire source, you could easily be wasting the precious contents of the extinguisher.

Julian Edgar

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