There are 6 classes of fire:-

SOLIDS such as paper, wood, plastic etc

FLAMMABLE LIQUIDS such as paraffin, petrol, oil etc

FLAMMABLE GASES such as propane, butane, methane etc

METALS such as aluminium, magnesium, titanium etc

Fires involving ELECTRICAL APPARATUS

Cooking OIL & FAT etc

Water extinguishers are suitable for class A

Foam is suitable for classes A and B

Powder is suitable for A, B and C

CO2 is suitable for B and E

Other types of extinguisher have specialised uses.

Edited by RT on 01/01/2013 at 20:25

"My understanding is that powder is more effective than foam, which isn't safe on electrical fires".....

The foam extinguisher I refer to is certified to 35 kv @ 1 metre, as are the all foam SPRAY extinguishers.

I've bought an Amerex 9 litre water MIST extinguisher for home which uses ditilled water and is also certified for the same electrical use. The Jewel E Series 6 litre water mist extinguisher is certified for Class F (cooking fat) and electrical fires.

Water - WITH ADDITIVE - extinguishers are also certified tby means of the accepted 35KV electrical conductivity tests.

However the post originated in the form of a vehicle sited extinguisher not an electrical situation.

I think the efficacy of powder versus foam could be argued in terms of the application it's being used for and could agree that powder injected through a small gap in to the engine compartment might smother and starve a fire better than foam - but inside a vehicle with a person trapped and with a fire associated with materials within the interior being alight then I'd favour the ideal of foam rather than risk choking the occupant with the powder.

As I said before, you can't beat the spray/jet from a high pressure hoserel that the FB use when they arrive....it's really trying to second guess the best course of action UNTIL they get there. And I guess either is better than nothing and we can't carry a selection of extinguishers around with us realistically.

I have CO2 at home and is good for confined spaces (provided there's no risk of suffocation) but it's rarely carried on vehicles so isn't especia;lly relevant to this topic and is less effective in the open than indoors. But agree that it's totally clean.

Some of us remember BCF (bromochlorodifluoromethane) and even CTC (carbon tetrachloride) which were excellent at vehicle fires and other confined uses...but were withdrawn as we all know. Co2 being the next best replacement for them.

Edited by KB. on 01/01/2013 at 21:00

The only clean, no-mess way to put fires out is with CO2. (not to be used on magnesium, of course!) way to put fires out is with CO2'

I don't think you really mean that. CO2 is great at what it does but it's not the answer for all fires...which is how it seems to sound here.

You are quite right to make the point, obviously other methods are better for some fires, the point was that for situations such as computer rooms CO2 or the halogen based gas extinguishants are the only type which doesn't cause more damage or add cleanup costs.

Halogen/Halon fire extinguishers have been illegal to own or use in the UK since 2003 although some critical applications have been permitted to continue using them.

Edited by RT on 01/01/2013 at 21:40

My experience with BCF is where the Safety Officer padlocked OFF the isolation valve in a big 11kV electricity substation, but didn't tell anyone. A short while later someone dropped a fag end into a cable trench and we lost the whole substation. When the Safety Officer was charged with this he just said that had a man been caught in the substation when the system went off then it would have been fatal. That would have applied to CO2, too.

The electrical department then installed a foam system in the main 11kV substation. The installer demonstrated that it was safe for users by staying, with invited guests, in an anteroom and setting the system off. Worked like a charm, but the people in there were so completely disorientated that they couldn't find their way out.

One of my young 'friends' once sprayed a party 'silly string' canister in my face and I had to sit down silently until I could breathe again. It seemed to take minutes.