Question:
Just a quick question - What type of fire extinguisher is best for preparing against engine fires?

Most places seem to sell 1kg powder fire extinguishers, but I have been told that this makes a complete mess of the engine (though obviously not as much mess as the fire itself would make).

Other options include water, though I would have thought that cold water on a hot engine would (potentially) do even more damage re: cracking; or gas (Carbon Dioxide or Halon). Are these available in handy 1kg sizes, and do they do the job?

Answer: There is no simple answer to the best thing to put out fires in general. All methods have benefits and drawbacks. However, remember that fire relies on heat, fuel and oxygen: extinguishers remove at least one component to put the fire out.

For Halon and CO2 to put out a fire, they must achieve a certain percentage of atmosphere in the area of the fire for long enough to put the fire out (ie they exclude oxygen). On a windy motorway, you may not be able to achieve this for an engine fire, although it is possible for an interior fire. For CO2, the percentage is much higher, hence larger quantities are required for the same effectiveness. Except in confined spaces, re-ignition of the fire is a distinct possibility (for example oil or petrol on an exhaust pipe, overheated insula tion on your electrics) since once the gas has blown away there is once again heat, fuel and oxygen. Although they appear good for an interior fire, both gases may cause suffocation, so should only be used when the occupants are free to escape.

Dry powder makes a mess, but it is very effective in the areas it can reach. Powder 'carpets' the fuel and does not blow away, thereby inhibiting re-ignition. This is very good in the open and for engine fires (where there is a lot of heat and fuel). It is less effective in confined spaces, where it will only act on areas it reaches.

Water takes out the heat, but is heavy and large quantities are required. It is not suitable for oil/petrol fires. Not sure of the merits of foam for car fires.

Most fuel stations have dry powder extinguishers on hand, and powder is used by Formula 1, I believe.