A fire extinguisher works to put out a fire because it removes one or more
of the 3 essential elements of fire.
maintain a fire you need HEAT, OXYGEN
Remove any one of these, and the fire will go out.
So for example a CO2 extingusher
will put out a fire because it displaces the oxygen. An air-water
extinguisher works because it cools the fuel, ie no heat. Dry
chemical fire extinguishers and foam extinguishers work by separating the
fuel from the oxygen. They form a film that covers the fuel and stops access
to the oxygen. The extinguisher usually only provides a temporary solution,
it is still important to ensure the rogue heat source is completely removed
or cooled to prevent re-ignition.
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Why are there different types of extinguishers?
Because there is more than one way to put out a fire, and because there are
different fuels, and even different types of heat, that need different approaches
to ensure the safety of the person trying to put out the fire. If you use the
wrong type of extinguisher on a fire, you could make it worse, and/or put yourself
||Consider electrical fires for example. The most important
thing to do to stop one, is to turn off the electricity, thereby removing
the heat source. This is not always easy to do, as the power switch is often
too close to the item on fire. If you try to put it out with a water, or
foam extinguisher, you run the risk of getting electrocuted because water
could conduct the current to the user. The ideal fire extinguisher to use
is a CO2 extinguisher.
Not only can it get in around difficult-to-reach objects, but it also leaves
no residue. However once the CO2 clears, the fire will re-ignite unless
the cause of the fire has been fixed.
Water or AFFF (Foam) extinguishers must not be used on deep seated cooking
oil/fat fires, when the water hits the hot oil it will convert to steam,
with a possible violent ejection of burning fuel from the container. The
blast from a CO2 extinguisher
on a fat, or a petroleum fire could cause hot burning fuel to be spread
chemical fire extinguisher is ideal for oil and fat fires because it
sprays a mist over the oil which chemically reacts to form "soap",
thus providing a barrier between the hot fat and oxygen. As soon as the
flames stop you must turn off the heat. Don't move the oil/fat until it
has cooled- if the soap layer is disturbed it may re-ignite.
Dry chemical or ABE
extinguishers work on the widest variety of fires by spraying a powder
over the fuel. They go by various names; DCP- dry
chemical powder, and ABE- referring to the fire types it can be used
upon. The powder is derived from bird droppings (!) and works because the
heat of the fire causes it to melt and form a film/layer over the fuel,
cutting off its access to oxygen.
Fire extinguishers are rated for
their ability to put out different type of fires. Read our article to learn
more about fire extinguisher ratings.
What size of fire extinguisher do I need?
is governed by the fire extinguisher Australian
Standards AS2444. In general the number, size and type
of extinguishers you need is determined by the area to be protected and
the type of fire risk. Other considerations are barriers that prevent access
to the extinguisher eg internal walls, machinery, pallets or storage shelves.
The presence of a fire sprinkler system will also change the requirement. So
the same building could require different extinguishers depending on how its
used, and what is stored there. For this reason Councils require a Fire
Safety compliance certificate whenever a new DA is requested.
size of a fire extinguisher is often
referenced by its weight eg a 4.5kg extinguisher.
However, the weight of a fire extinguisher does not necessarily describe its
fire-fighting capacity. Different brands of fire extinguishers, vary in their
ability to put out fires. When comparing prices and value for money look at
the ABE rating, not just the weight. For example
at the home
fire extinguisher level, a 1kg fire extinguisher could vary wildly in its
ability to put out a fire: a cheap one might have a 1A:10B:E rating, whereas
ABE extinguisher has a rating of 1A:20B:E. That's twice the ability to put
out a B type fire.
Have a look at our article on choosing a fire extinguisher
How to use a fire extinguisher
Signs above the extinguisher tell you what sort of fire it can be used on.
- Always test the extinguisher before proceeding to the fire.
- Ensure you have an escape route.
- Most fire extinguishers only discharge for seconds, not minutes, so don't
tackle a fire unless it is safe to do so and you are trained.
- The rule of thumb is if you can not put a fire out with one extinguisher,
then the fire is too big to fight - call emergency 000
To use a fire extinguisher, follow
the PASS rule - acronym for Pull, Aim, Squeeze,
Fire Extinguisher Training for employees
- Pull the pin,
- Aim the extinguisher at the base of the fire,
- Squeeze the handle,
- Sweep it back and forth.
For a more comprehensive article on how to use a fire extinguisher go to the
a fire extinguisher has been used or discharged it should be replaced or
refilled, even if it was not emptied. This is a requirement of the Australian
Standard, but it also makes common sense. In particular if you use a dry chemical
powder extinguisher, the powder residue left in the valve could lead to a slow
leak of pressure, meaning it will be useless next time you try to use it.