Fire Extinguisher Ratings Explained

Updated 2nd September 2020

What's a Fire Extinguisher Rating?

All quality fire extinguishers that comply with the modern manufacturing standard BS EN 3, will be printed with a code that gives the ‘fire extinguisher rating’.

This rating helps you to understand which types of fires the extinguisher is capable of dealing with and helps risk assessors and business owners understand their fire extinguisher needs. The classes of fire for Europe and the UK are different to those used in the USA and Australia, so if you are overseas you will need to read the labels carefully.

The rating helps you to understand which types of fires the extinguisher is capable of dealing with

Understanding Fire Extinguisher Ratings

A fire extinguisher’s rating consists of 2 parts: a number and a letter.

The letter part of the rating denotes what class of blaze this fire extinguisher is suitable for. If you’re not sure what type of fire extinguisher to use for each class of fire, take a look at our blog that explains this in detail.

The number part of the rating simply describes the size of the fire that the fire extinguisher can extinguish. The larger the number before the fire type letter, the larger the fire that extinguisher can tackle.

Each fire class rating is measured differently. Class A fire ratings are calculated by how many stacks of burning material the extinguisher can put out and Class B ratings are established by the number of litres of flammable liquid that can be extinguished.

Each fire class’s rating is measured differentlyFire extinguishers that can be used on electrical fires such as some Foamspray and CO2 models will be marked on the body of the extinguisher as ‘Approved to 35kV dielectric test’. This means it would have been dielectrically tested to 35000 Volt (35kV) and can be used on or near electrical appliances.

For example, our 2L Foamspray extinguisher has a rating of 5A 55B. This fire rating indicates that it can tackle A class fires up to size 5 and B class fires up to size 55. 

This fire extinguisher can tackle up to 5 ‘stacks’ of pre-determined combustible solids and up to 55 litres of the tested combustible fuel.

Fire extinguishers used for Class C & D fires do not carry a number rating.

Why are Fire Extinguisher Ratings Important?

These ratings help us to establish whether the given risk is properly accounted for during Fire Risk Assessments and gives us the ability to estimate the type and number of fire extinguishers required when hiring them for events.