Fires involving flammable liquids are categorised as a Class B fire. This type of fire is incredibly volatile and dangerous and can spread very quickly causing danger to life. Understanding exactly how to extinguish a fire involving flammable liquids is vital.
Each type of fire is unique in both how it starts, how it behaves and how it needs to be handled. Once you understand the 6 classes of fire you will understand how to put the fire out correctly and safely.
What is a Class B Fire?
Class B fires involve the combustion of flammable liquids. This type of fire is very dangerous as it involves volatile liquids like petrol, diesel, oils, solvents, and some paints.
Flammable liquids have a relatively low ignition temperature (under 100°C). They are also easy to ignite in the presence of naked flame, which means special storage precautions should be taken. Flammable cabinets need to be used in workplaces which store hazardous substances.
Obvious workplaces at risk of Class B fires include petrol stations and factories. However they can also be found in environments such as schools, nurseries, offices, and retail. Class B fires are dangerous because they burn very quickly and cause extensive damage. They also produce thick smoke which is toxic.
Class B fires represent an extreme hazard to life, and are very challenging to extinguish.
Fire Symbol
The Class B fire label has a B in the right hand side corner and an image of a petrol can underneath.
See Also:
- Petrol fire extinguishers – our guide on which equipment you need to put out a fire involving burning fuel.
- Fire Extinguisher Types & Colours – guide to identifying fire fighting equipment by label colour codes.
About Class B Fire Extinguishers
You should use a dry powder extinguisher on a Class B fire. Powder extinguishers create an inert layer over the fuel, smothering the flames. Powder extinguishers also inhibit the chemical reaction which causes the fire.
However, you can also use a:-
These extinguishers work by depriving the fire of its oxygen supply.
Dry Powder Fire Extinguishers
Powder extinguishers form a layer on top of the fuel. This smothers the oxygen supply that is keeping the fire lit.
The dry powder also interferes with the chemical reactions going on in the fire itself. Sometimes, dry powder extinguishers can also be used on Class C fires which are usually caused by flammable gases.
You may often hear dry powder extinguishers referred to as ABC. This is because they can be used in all 3 of those fire types.
Foam Fire Extinguishers
Foam extinguishers work on Class B fires by suppressing the oxygen. This in turn dulls the fire until it goes out.
It can be used on other types of fire too, including burning furniture and other solids. Foam extinguishers also handle burning petrol well.
Fire Blanket
A fire blanket can be used to tackle a very small flammable liquid fire. It should be placed on top of the fire, and it will suppress the oxygen. This in turn will extinguish the flames.
CO² Fire Extinguishers
These omit a cool burst of carbon dioxide which immediately cools the fire. The release of CO2 also reduces the oxygen levels rapidly which puts out the fire.
How to Extinguish a Class B Fire?
Class B fires are best tackled using a dry powder extinguisher as these inhibit the chemical reaction that drives the flames. However you can also use foam or CO² fire extinguishers. These will suppress the oxygen.
Class B fires tend to ignite and spread fast and can become out of control quickly. Water should never be used on a flammable liquid blaze.
Types of Extinguishers That Should Not Be Used
Never use a water fire extinguisher on a Class B Fire, it will greatly intensify the fire. Water and flammable liquids are an explosive combination.
Water applied to a Class B fire will vaporise and cause a fireball which could be catastrophic. The flames will spread more quickly, and the fire could burn out of control.
Class B Fire Prevention
Of course, prevention is key and having a solid health and safety plan in place for fire safety will reduce the risk of a fire occurring.
- Any flammable liquids should be safely stored in or flammable cabinet if possible.
- Spill proof containers should be used.
- Pour only what is needed and no more.
- Do not put flammable liquids close to any potential ignition sources.
