What Is a Class B Fire? The Complete Guide

When determining fire safety in the workplace, one of the most dangerous fire types to be aware of is Class B fires. These fires involve flammable liquids typically found in workshops, garages, kitchens, and across many commercial sites.

In this guide, we give you the full rundown of Class B fires, including what they are, what causes them, how to safely extinguish them, our top recommendations for Class B fire extinguishers, and how you can easily identify them.

At Fire Protection Shop, we have helped thousands of businesses stay compliant and protect what matters most. By the end of this blog, you'll feel confident about how to handle Class B fire risks and what extinguishers offer the best protection.

What Is a Class B Fire?

A Class B fire is a fire that burns because of flammable liquids. Flammable liquids include liquids such as petrol, diesel, oil, alcohol, and solvents. If the flammable liquid reaches its flashpoint (typically below 60⁰C), enough vapour can be released to form a flammable mixture with air that can ignite if exposed to a flame, spark or hot surface and produce a fire.

What Do Class B Fires Include?

Class B Fires include flammable liquids which are more common in the workplace and at home than you may be aware of.

Examples of common flammable liquids at home include:

• cooking oil

• alcohol

• lighter fluid

• aerosol sprays

• perfume and aftershave

• some household cleaners

Examples of common flammable liquids in the workplace include:

• petrol and other fuels

• solvents in industrial products (such as cleaning fluids, paint etc)

• flammable chemicals

• cellulose paint thinners

• engine oils

• grease

What Causes Class B Fires?

Class B fires are caused by enough vapour being released from a flammable liquid to be able to ignite when exposed to a flame, spark or hot surface. It is important that flammable liquids are stored correctly and at the right temperature.

How To Extinguish a Class B Fire

To safely extinguish a Class B fire you should use Class B fire extinguishers. It is important to note that not all fire extinguishers work on all fire types, and some can make the situation worse. And remember never to use water on a class B fire - this can make it grow rapidly!

What Are Class B Fire Extinguishers?

Class B fire extinguishers are designed to safely put out Class B fires. These include:

• CO2 Fire Extinguishers - identified by a black coloured label with the text CO2

• Foam Fire Extinguishers - identified by a cream coloured label with the text Foam

• Dry Powder Fire Extinguishers - identified by a blue coloured label with the text Powder