Fire Extinguisher Classifications - How to Understand Each Class of Fire Extinguisher

All fire extinguishers are given a classification, primarily in order to show what kind of fires they are safe to use on. This is important because using an extinguisher on the wrong type of fire can have disastrous consequences. For example, if you use a water extinguisher on a fire involving any electrical equipment, you are risking electrocution and possible death.

Classifications are made up of letters and numbers. The letter part of an extinguisher classification tells us what fire type the appliance is suitable for. Each type of fire is given a class, which is designated by a single letter. When you look at the classification on the side of an extinguisher, what you see will be one or more letters, showing all the types of fire that the appliance is safe to use on. So there may be one letter, or several.

The other thing that fire extinguisher classifications do, is tell us something about how effective an extinguisher is, or 'how much' fire it can put out. This is indicated by a number which is shown next to the letter on the classification. A higher number indicates that the appliance can deal with a bigger fire. The numbers correspond directly to set fire tests that the extinguisher has been subjected to. The rating an appliance ends up with will generally relate to the actual amount (distances or areas) of fire that it was able to extinguish. For example a classification of 13 means that the appliance was able to extinguish 1.3m of fire in the test situation.

On every extinguisher you will see one or more letters, and a number, giving you important information about the type of fire you can use it on and how effective it is likely to be. This kind of information can be crucial when you have to make a decision about whether to tackle a fire or not.

There are slight differences between fire extinguisher classifications in the UK and in the US. The UK system is the same for whole of Europe and Australia too.

Extinguishers for dealing with fires involving everyday combustible matter such as paper, cardboard, wood or textiles are given an 'A' classification. This is the same in both the UK and US.

Extinguishers designed specifically for use on flammable liquids such as oils, spirits and petrol, are given a 'B' classification. Again, this classification is the same in the UK and US.

In the UK there is a separate class C rating for extinguishers that are safe to use on flammable gases, such as natural gas or propane. In the US this category is included in the 'B' classification.

Appliances that deal with fire on combustible metals have a 'D' classification in both the UK and US.

In the UK, electrical fires do not have a separate classification, though they are occasionally wrongly referred to as class 'E'. Electricity is viewed more as a cause of fire and source of ignition than a classification in the UK. Remove the electrical supply and the fire becomes a class A, B or whatever. In the US electrical fires are known as class 'C'.

Finally, the specialist appliances which are the only ones safe to use on burning deep fat fires are classed as 'F' in the UK and 'K' in the US.

Fire extinguisher classifications give you valuable information that you need if you are faced with a fire. The information on the extinguisher is only of use if you know for sure what is burning. If you have any doubt about what is actually on fire, you should not attempt to put it out.