Five agents cover the portable extinguisher range in the UK and none of them covers everything. The all purpose fire extinguisher people look for does not exist, because the ways of stopping a fire work against each other: what cools a paper fire spreads an oil one, and what smothers a liquid fire leaves embers glowing.
The five, in one place
Water, red banded, class A only, cools burning solids. Foam, cream banded, classes A and B, blankets liquids and cools solids. Carbon dioxide, black banded, class B and safe near live electrical equipment, leaves no residue. Dry powder, blue banded, classes A, B and C and electrically safe, but discouraged indoors. Wet chemical, yellow banded, class F, the only agent for cooking oil.
Why there is no universal one
ABC powder comes closest and is still not class F rated, is not class D rated and is discouraged inside occupied buildings because a discharge blinds the room. An agent that cools well carries water, and water is exactly what must not reach burning oil or metal. The trade off is physical rather than commercial, which is why a building needs a mix chosen against its own risks.
Reading the pictograms
The label carries pictograms for each class the extinguisher is rated for, with a crossed out symbol for classes it must not be used on. Those pictograms are the same across manufacturers and are the fastest way to check an unfamiliar extinguisher in a hurry, faster than reading the band and much faster than reading the text underneath it.
Choosing the mix for a building
The fire risk assessment identifies what can burn and where, and the extinguisher provision follows from that: class A ratings for the general areas, foam or carbon dioxide where liquids or live equipment are, wet chemical in the kitchen, powder outside and in vehicles. Provision is specified in ratings and locations rather than in a count of cylinders, because two extinguishers the same size can be rated very differently.
Questions people ask about different types of fire extinguishers
Is there one extinguisher that covers all fires?
No. ABC powder is the broadest and still excludes cooking oil and metal fires, and it is discouraged inside occupied buildings. A building needs a mix matched to its own risks.
What do the symbols on an extinguisher mean?
They are the fire class pictograms showing which classes the extinguisher is rated for, with crossed out symbols for classes it must not be used on. They are standard across manufacturers.
How many extinguishers does a workplace need?
That comes from the fire risk assessment, expressed as ratings and locations rather than a number of cylinders, because extinguishers of the same size can carry very different ratings.