Fire extinguishers

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Originally Posted by Mr Whippy

Is there a lot of magnesium used in aircraft and is this the reason they are still allowed to have them.

I still have one my self kicking around in the shed somewhere.

Dave.

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Still a reasonable amount of magnesium alloys in aircraft.
The good thing about BCF is that they work well in confined spaces (aircraft cabin) The BCF extinguishers dont leave powder or foam everywhere nor airborne particlesfor people to inhale. While BCF will still be inhaled (its a gas) anyone suffering after inhalation should make a full recovery, with no long term health effects. Lung fulls of powder often bring about long term/ serious repiratory problems.
The smoke and fumes from a cabin/cockpit fire are horrendous and the less visible stuff floating around the better.

So the likelihood of a fire airborne and the almost guaranteed loss of life in the aircraft and on the ground weighed against environmental issues keeps the BCF in aviation use.

I still get a wry smile when someone pipes up about extinguishers on board. While I like to protect the environment, I think the smoking hole in the ground or town would make bigger impact than BCF being discharged.

cheers

cheers

Don't know how effective BCF would be on burning metals such as magnesium. Back in the 'old days' we were told Purple K (a specialist type of dry chem) was the go for these fires and the car racetrack fireys certainly had them for this purpose though I've never seen Purple K used. One thing that BCF has in common with Purple K is that they both re-wrote the training manuals on fire extinguishing. Conventional wisdom had it that breaking the fire triangle, fuel-heat-air, by removing one of them extinguished a fire. What BCF and Purple K have in common is that they disrupt the chemical reaction of a fire causing its extinguishment, which was a whole new concept.
BCF as an extinguishing agent is very effective, especially in closed or difficult to get to spaces and its withdrawl from the market left a major hole which was never really filled. ABE powders were not common, were very messy and (comparatively) not as effective as BCF. BCF extinguishers were light, relatively cheap, easy to use and most of all safe and effective to use on most types of fires. It was interesting to watch BCF at work extinguishing a fire. The flames appeared to 'run away' from the BCF as it was applied, a very strange experience to watch as it killed a fire rapidly and a little bit went a very long way. The biggest problem was potential flashback as the BCF dissipated which is why it wasn't so good in open spaces.
One place where BCF was very effective was in attacking vehicle engine fires. A small puff through the radiator/grille before popping the bonnet dampened the fire enough so that it wouldn't flare up as the bonnet was opened allowing you get access without getting scorched. Water was prefered as the follow up as it was cheap, effective and less damaging than dry chem.
BCF may have been damaging to the ozone layer (the politically correct green theme of the day), but when you consider the comparative amount of hydrocarbon propellants and R12 that was being released into the atmosphere the amount of BCF released was minute. There may have been a lot of BCF extinguishers hanging on walls but the gas was contained and was of no harm. It's all history now. The banning of BCF extinguishers was an absolute windfall for the fire protection industry as they were replaced with less effective/versatile dry chem and CO2 extinguishers; I often wonder if this wasn't the whole aim of banning them in the first place.

Deano:)