Every
fire extinguisher has an alphanumeric rating that tells you what types of fires it can extinguish as well as the size of fire it can put out.
The letters stand for the class of fire the extinguisher can be used against:
A – ordinary combustibles (wood, paper, plastic, etc.)
B – flammable liquids (oil, gas, petroleum, etc.)
C – electrical equipment
D – metals
K – cooking oils and fats ( specialty extinguisher - a Class B works on these fires too)
Type A only extinguishers are usually a liquid type extinguisher (typically water under pressure) and should only be used on ordinary debris type A fires - they can cause a flammable liquid fire to spread by floating the burning fuel on top of the water, can shock you if used on electrical fires or cause an explosive expansion of fire if used on flammable metals (as in burning magnesium not hot steel)
Multipurpose extinguishers ( typically Dry Chemical, CO2) can be used on different types of fires and will be labeled with more than one class, like A-B, B-C or A-B-C.
The numbers give an idea of how much or the size of each type of fire, that the extinguisher can put out (if it is deployed correctly) . Every number before the A means it is as effective as 1 ¼ gallons of water. ( so 2A means the fire extinguisher is as effective as about 2 1/2 gallons of water on an ordinary fire, and so on) The numbers before B and C are a measure of the amount of square feet the fire extinguisher can put out . For example, a 10:BC fire extinguisher can extinguish a fire about 10 sq ft. in size.
Check that the extinguisher you intend to use is suitable for the type of fire encountered (eg a water extinguisher must never be used on any fire involving ENERGIZED electrical equipment.- I know but in an emergency, sometimes the brain doesn't fire on all cylinders)
Know how to use the extinguisher correctly.
There are four (4) basic steps for using modern portable fire extinguishers.
The acronym
PASS is used to describe these four basic steps.
- Pull (Pin)
Pull pin at the top of the extinguisher, breaking the seal. When in place, the pin keeps the handle from being pressed and accidentally operating the extinguisher. Immediately test the extinguisher. (Aiming away from the operator) This is to ensure the extinguisher works and also shows the operator how far the stream travels
- Aim
Approach the fire standing at a safe distance. Aim the nozzle or outlet towards the base of the fire.
- Squeeze
Squeeze the handles together to discharge the extinguishing agent inside. To stop discharge, release the handles.
- Sweep
Sweep the nozzle from side to side as you approach the fire, directing the extinguishing agent at the base of the flames. After an A Class fire is extinguished, probe for smouldering hot spots that could reignite the fuel.
- If it doesn't go out - get out - things can be replaced, People can't
The things to consider in what you need for your shop are the what's, where's and how's your shop is set up and the potential exposure your activities put your fire risk at.... Size of the shop, concrete floors (don't burn but cause greater spark/hot object bounce possibilities), gravel floor (harder to keep clean of dust,oil and debris), how busy you are, how often you work alone, as well as how good/much your housekeeping time and skills are. There is no one size fits all here (and remember a quick prayer before starting work doesn't hurt)
Now to answer your question (my God I'm a wind bag):
I have a couple of 2 gallon, air pressure type A squirt can extinguishers, a couple of 1A:10BC Dry chemical extinguishers and a 50' garden hose hooked up to my shop water system hanging on the walls. I also have a hot water pressure washer to clean off grease and oil from the area around the area I'm welding on the equipment I work on if needed and always try to limit where sparks, metal slag and where hot metal can drop and bounce around. I keep flammable liquids in a closed fire rated cabinet, and have the shop laid out well. It's not over kill - I'm a little anal, was a boy scout and have been a full time paid firefighter for the past 32 years - LOL)