Fire extinguisher for workshop- advice

Witnessed a zane starting to go up with petrol pumping from the fuel line - one person grabbed a powder extinguisher, I grabbed a large rag - the rag was the most effective, snuffing out the flame immediately and giving us time to switch off the ignition. I need to get a good extinguisher in the workshop. Have one, but not sure of type or expiry!
 
The Sock said:
CO2 isn't great on fuel fires, in my experience, particularly at injection pressures.
Flying, we got to keep Halon, which is the D's Bs on fires.
Not fun to breathe, but better than burning.
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Halon is pretty much banned worldwide for general purpose fire extinguishers because of it's ozone depleting property. It's still permitted in special applications like aircraft because it's not really practical to carry a massive great water tank on a plane for a sprinkler system, and CO2 would asphyxiate the passengers. Halon is not toxic to breathe. It's pretty much chemically inert. Like helium, it's only dangerous if it's at a high enough concentration to displace the oxygen in the air. I've breathed it myself with no ill effects. It has the opposite effect on your voice than helium. It makes your voice deeper.

I'm old enough to have been working in the design of fire protection systems when halon was routinely used in areas where water sprinklers were undesirable, like computer rooms and historic document vaults. I was the construction OIC on several halon installations. Back in the good old days we'd actually test systems by doing a full gas release. Depending on the size of the installation, that could be several tons of halon gas vented to the atmosphere all at once. I reckon I played a greater role than most people in making the hole in the ozone layer, but we didn't know any better in those days.

I vividly remember running a halon fire suppression system test in a film library (old cellulose film is particularly flammable). The place was full of old priceless historic and irreplaceable films. All stacked on high shelves in the big flat film cans that were used to contain movie reels. The place was wired up with sensors to check the concentration of halon gas in various parts of the warehouse. The doors to the warehouse were then closed and we activated the system. There was an almighty "WOOSH" and the doors bulged outwards as the gas was released. Dust blew out of all the crevices under and around doors. After the pressure surge had settled down and the instrument recordings checked, we confirmed that the system had worked as designed and declared it a successful test. Then we opened the doors. The entire floor of the warehouse was covered about a metre deep in a tangled mess of ten thousand miles of unravelled movie film. The gas nozzles had blown about 90% of the film cans open and strewn them all over the place. The manager of the storage facility went as white as a ghost and just stood there speechless. We packed up our gear and left someone else to sort out the film spaghetti. At least it wouldn't have burned if there had been a fire.

Dry powder (basically just baking soda in a pressurised can) became the default replacement for halon in most cases.

Dry powder extinguishers don't really have a use-by date. They can last until the canister rusts out. But in commercial applications they have to be checked and tagged on a regular basis. That doesn't apply in domestic applications (at least in Australia - I dunno about other countries) so you can do your own extinguisher maintenance. All you need to do is to check that the pressure gauge is in the green zone. If it's lost pressure then you need to replace it. If the pressure is good, then turn the extinguisher upside down, give it a whack on the bottom with a rubber mallet and shake it up and down a few times. That's simply to stop the powder settling into a dense clump in the bottom of the canister. Do that every 6 months any your extinguishers will be perfectly functional for many years.
 
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