As dan pointed out, there will be regulations
(48' UK flagged vessel?) requiring multiple extinguishers AND no doubt they will need to be "approved" by someone, the same way that in the US they must be USCG approved. (Which, literally, can mean that there's just a more expensive mounting bracket supplied and required to be used.)
I would suggest that you contact a local fire department and ask if they ever demonstrate extinguishers to the public. Again, here in the US things may be different, but folks are always dropping off expired extinguishers and the firemen are usually quite happy to show folks how they work
, by using those.
The typical "yellow powder" type make an unholy mess. It gets into everything within 50 feet and takes weeks of cleaning
and vacuuming to get out. It is also not good to breath, goggles and filter masks are often worn by demonstrators. And, if corrodes electrical parts
and kitchen appliances
. So yes, it puts out fires, and yes, it is cheap
, but it has downsides.
There's a variation of this (Type "K") recently approved in the US, which uses plain white baking soda instead. Type K are designed for Kitchen fires, mainly grease fires, and the nozzle on them spreads the powder over a wider area at a lower pressure, so it won't push burning grease further away from the stove
. Also non-corrosive and much easier to clean up. Worth considering in the galley
or in any location like an engine bay where the area is fairly contained and full of electrical parts
Personally I like CO2 when it is applicable. I smelled a funny
bromine smell one night, at least I think that's what you'd call it. And found smoke coming out of a hall closet. I didn't ask, I just cracked the door open, inserted a CO2 horn and squeezed. It turned out to be spontaneous combustion of either a magnesium fire starter, or hurricane
matches, in some camping goods. (The main damage fortunately was limited to a tent fly, which is now used as a poncho by the seven dwarves.) But any type of dry powder in there would have been a full day or more of clean out.
So they all have distinctions, and there's some merit in "universal" because you really don't have a lot of time to say "Do me a favor, go forward and get the extinguisher from the starboard locker?". The real surprise is that a "small" fire doubles in size every 30 seconds. A small extinguisher can put out a fire about the size of a fully involved desk waste basket. And then 30 seconds later...too late, the fire is too big.
Also of note, upholstery foam is usually polyurethane
and gives off toxic smoke. If your cushions
are of recent vintage and have fire-retardant chemicals in them, that's a little better but they are still "toxic fuel". Being able to respond quickly, and adequately, or to evacuate promptly, really needs to be thought out, and planned ahead.
And if you've never used an extinguisher, really, find a way to get a demo. Just seeing it on YouTube doesn't quite match the real experience.