Dry Powder extinguishers are DANGEROUS on yachts.

**VicS** · 09-03-10, 21:52

thank DeepJoy for confirming what I had read somewhere but couldn't put my finger on, that the powder is Sodium Bicarbonate.

Dry powder extinguishers used to be sodium bicarbonate and maybe some still are but a different powder (a phospate ??) is now used to make them suitable for a wider range of fire types.( AB&C rather than just B&C ???)

IIRC it melts and encases the "fuel" when that is solid and so seals it off and helps prevent re-ignition. Bicarb was not good at preventing re-ignition of solid fuels eg wood.

**DeepJoy** · 09-03-10, 22:10

Vic,

Ammonium phosphate is the ABC type of dry powder (Monnex), and is what you might find in 'industrial' dry powder extinguishers. Potassium bicarbonate is also used. However, the type which tend to be used on small boats like ours are 'domestic' typem and will most likely be sodium bicarb. I work in the chemical industry, and we still use sodium bicarb for many installations.

The bottom line remains the same though - it is better to have any type of extinguisher on the boat than to avoid having one because of possible health concerns

**alan_d** · 09-03-10, 22:29

Originally Posted by Salty John

I used a dry powder extinguisher to put out a fire in our engine bay when we were struck by lightning. Yes it was messy, but I was in control the whole time, no white-out, no noxious fumes and I stayed inside the boat the whole time (huge lightning storm raging outside!). I was impressed at how simple it was, but we were vacuuming up white powder for a couple of hours.

Look, don't come spoiling this thread with your empirical experiences ...

**lw395** · 09-03-10, 22:46

What's the yellow area in your graph, Ubergeekian?

**VicS** · 09-03-10, 22:53

Ammonium phosphate is the ABC type of dry powder (Monnex), and is what you might find in 'industrial' dry powder extinguishers.

The extinguishers I bought recently from Lidl are ABC rated. I assume, perhaps wrongly, that they contain what you now confirm to be ammonium phosphate.

**tinkicker0** · 09-03-10, 23:26

I'm an elfin safety bod and also conduct fire training.
Elfin safety spend a lot of time dispelling stupid "health and safety sez so" rumours.

How much time do you think your puny 2k ABC in a marine environment will last? About 10 seconds if you are lucky, have it serviced every 12 months and keep giving it a shake now and then. How long do you intend to hang around?

The smoke in the cabin will do for you far more efficiently than ABC powder.

As for CO2, read your fire extinguisher placards "not for burning paper or textiles" it sez. A great way to make a small paper or textile fire into many fires.

True, powder are not ideal for enclosed spaces and can cause transient breathing difficulties, but they are certainly not classed as hazardous.

However, it would be wrong to post without divulging my first choice of extinguisher on a boat, which would be AFFF foam. Size for a 34b rating would be around 3 kg. You should have at leat two of these.

Better to have several smaller type 34b ones located around your boat, than one large one, for if the large one fails or you can't reach it........

Of course bigger is better, but who wants 9 litre foam extinguishers everywhere. Far better to have enough extinguisher and spend more effort preventing fires from occurring.

**maxi77** · 10-03-10, 07:49

Originally Posted by Haven't-a-Clue

Some interesting and conflicting statements here re carbon monoxide - CO - and carbon dioxide - CO2. A few facts here as I had to learn them as part of my training: CO2 kills by asphyxiation, ie displacing the oxygen the brain and vital organs need to function. It combines with haemoblobin at roughly the same rate as oxygen does, so it is NOT instantly lethal. That's what respiration at its' basic and scientifically correct definition is. You breath in air approx 20% oxygen -O2 - and 0.04% CO2 (and of course, nitrogen, although we'll dismiss that in our discussion). You breath out oxygen approx 16% and CO2 approx 4%, a straight gas exchange (remember I use this kind of meauring equipment every day as part of my job, so I know the numbers). Therefore, we can sort of presume that O2 and CO2 have roughly the same ability to combine with haemoglobin. So when you're exposed to a high level of CO2, respiration depth and rate increase and
you start coughing, that's the signal to move higher, above the level of CO2 (heavier than air). CO, however has 15 times the ability of both O2 and CO2 to combine with haemoglobin..............so one good lung full is the equivalent of 15 deep breaths of CO2 and you don't usually survive, very difficult to reusus someone with CO poisoning 'cos of the amount of carboxyhaemoglobin that has to be got rid of, whereas CO2 can be replaced fairly quickly with oxygen. It's one of the ways we wake people up after anaesthesia, replacing the anaesthetic agent with oxygen. Hope this helps to explain the difference and dangers between CO and CO2.

Ian

Very true and you can live reasonably well with higher proportions of CO2 than normal as long as the pressure stays close to 1 atmosphere. You do however have to factor in the impact of the brain getting less oxygen. As the ammount of oxygen you get falls your ability to act rationaly dissapears very fast, which is why in planes you are told to always fit your oxygen mask before helping any one else.

**rosssavage** · 10-03-10, 09:01

Galadriel - unfortunately we are no longer permitted to carry halon extinguishers on commercial aircraft, we now use BCF. Id like to know why we can't use BCF on boats - having used it in galley fire training drills it is very very effective.

And yes, put your mask on before helping anyone else in an aircraft decompression - crews are taught to sit down immediately and don a mask - even if that involves sitting on the nearest passengers lap and grabbing the spare mask that is supplied at every seat row. Bizarrely, we're then told to get the passenger to put their arms around us and hold on! (to restrain the crewmember during the drop-out-the-sky descent.)

Vics - any idea why we aren't allowed BCF on boats?

**vyv_cox** · 10-03-10, 09:13

Originally Posted by rosssavage

Galadriel - unfortunately we are no longer permitted to carry halon extinguishers on commercial aircraft, we now use BCF. Id like to know why we can't use BCF on boats - having used it in galley fire training drills it is very very effective.

And yes, put your mask on before helping anyone else in an aircraft decompression - crews are taught to sit down immediately and don a mask - even if that involves sitting on the nearest passengers lap and grabbing the spare mask that is supplied at every seat row. Bizarrely, we're then told to get the passenger to put their arms around us and hold on! (to restrain the crewmember during the drop-out-the-sky descent.)

Vics - any idea why we aren't allowed BCF on boats?

I think you will find that BCF and halon are the same thing. Bromochlorodiflouromethane is Halon 1211 and is one of the banned extinguishants.