What is a Class B Fire Extinguisher Used For?

Did you know that there are 5 different classifications of fires? While Class A is the most common type of fire, involving wood, paper, or textiles, Class B fires involve more than these standard combustible materials. A Class B fire includes elements like flammable liquids, which can make putting out this type of fire much more complicated. In this article, we explain exactly what a Class B fire is, as well as how to extinguish and prevent this highly dangerous occurrence.

What Are Class B Fires? 

Class B fires may occur anywhere flammable liquids or gases are stored or used, and cannot be put out using just water. This fire classification typically does not include cooking fires, even though they are commonly caused by flammable cooking oils and/or grease.

Koorsen Fire & Security gives their definition on what constitutes a Class B fire:

“…Class B fires are ones in which flammable liquids and/or gases become involved. They are the fuel source in the fire triangle (fuel, heat, oxygen + chemical reaction). Flammable liquids include gasoline, diesel fuel, oils, tars, petroleum greases, solvents, alcohols, and oil-based paints. Flammable gases include things like propane, hydrogen, and butane. The fuel sources of class B fires (gases and liquids) can be quite volatile and cannot be extinguished by water, which will only make the fuel source spread, thus spreading the fire. That is why it is important only to use extinguishing agents and methods designed specifically for Class B fires.”

How Do You Extinguish a Class B Fire?

Ensuring that you extinguish a Class B fire using the correct type of fire extinguisher is detrimental to making sure your fire does not continue to spread. While Class A fire extinguishers are the most common types of fire extinguishers, they should never be used when extinguishing a Class B fire.

Elite Fire explains more on why a water fire extinguisher should never be used on a Class B fire:

“One method of fire combat which should not be used in the event of a Class B fire is a water fire extinguisher. This is because a lot of flammable fuels have a specific gravity of less than 1.0 – such as gasoline or oil – and this means they will float along the surface of the water. Therefore, the fire will not be extinguished and will simply continue to burn along the top of the water.”

Preventing a Class B Fire

Prevention is always the best method of fire safety, and it’s important to take precautions to ensure that a Class B fire does not break out in the first place. And while you should avoid storing flammable liquid as much as possible, there are safety precautions you can take to keep these liquids away from any potential heat source.

Fire Protection Online tells us more on how Class B fires can be prevented:

“As they can be very dangerous, it pays to take precautions to prevent a class B fire from breaking out. You should never store more flammable liquid than absolutely necessary, and well away from sources of ignition. If it’s possible, you could also consider storing liquid in flammable storage cupboards made of steel. They work by creating a barrier between a potential fire outside, and the flammable liquid stored in them, for around 30 minutes. So remember to not use water, and instead have appropriate fire extinguishers close by, just in case.”

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