No two fires are ever the same, and that means that how we fight them also varies. Class B fires involve flammable liquids, which because of their chemical composition, behave differently from other types of fire sources like wood, paper or electrical faults.

So, what is a Class B fire? Well, put simply, it’s any type of fire that involves a flammable or combustible liquid, which includes petrol, paraffin, oil-based paints, varnishes, alcohols, including ethanol and methanol and some cleaning solvents.

In this guide, we will go into more detail about Class B fires, including common causes, how to prevent them and, perhaps most importantly, how to suppress or extinguish them safely and effectively. 

Common causes of Class B fires

Like the majority of fires, Class B fires can start quickly, with little warning and through relatively small mistakes or oversights. A simple lapse in concentration can have disastrous consequences and, as most flammable liquids are used in professional environments, can have serious repercussions for the business as well as the individuals involved.

Common causes of Class B fires include:

• Leaks and spillages (from refuelling or cleaning)
• Improper storage (poorly sealed containers or storage near heat sources)
• Equipment failures (including valves and pipes, or damaged fuel lines)

These types of issues pose real issues in industrial, automotive and workshop environments where the use of gases, fuels and heat sources is commonplace. To mitigate the risk of fires (of all types), they require close control and fast resolutions to prevent small spillages or minor damage from turning into major fires.

How to avoid Class B fires

The best way to avoid any type of fire is to remain vigilant and careful when working with anything that could cause a fire, but this becomes even more important when working with highly (and instantly) flammable liquids.

Safe storage and handling can instantly reduce the risk of a Class B fire starting, and regardless of whether you’re simply moving a container or using the contents, these tips will help you reduce the risk and avoid a Class B fire:

• Store liquids in clearly labelled, sealed containers
• Keep flammable liquids and gases away from heat, open flames or potential sparks
• Ensure good ventilation to prevent vapour build-up
• Use spill trays and containment units in high-risk areas
• Ensure that all staff are trained in safe handling procedures and emergency actions
• Regularly inspect and maintain equipment which uses or handles flammable liquids

How to suppress a Class B fire

Suppression of Class B fires is difficult because of the speed at which these types of fires can take hold. However, it can be done by:

• Turning off the fuel supply where it is safe to do so
• Breaking the fire triangle by cutting off oxygen through a fire blanket or fire extinguisher
• Using automatic fire suppression systems such as the PyroCloud fire suppression range in enclosed areas
• Closing doors or vents to limit airflow and slow the spread of the fire

You can watch our Q&A video about how the PyroCloud system works on our YouTube channel

If a Class B fire has already taken hold, the priority should always shift to extinguishing it rather than merely suppressing it. Extinguishing any fire, but especially Class B fires, depends on the level of training received (and the confidence of those trained), the nature of the fire, and the available fire safety equipment.

If those trained in using extinguishers and other firefighting equipment are not confident in tackling the fire, wait for the Fire Brigade to arrive and evacuate the premises as quickly and safely as possible.

What extinguisher to use on Class B fires

When extinguishing is a viable option, you have three types of extinguishers to choose from to tackle Class B fires:

• Foam extinguishers: These form a smothering layer over the surface of the liquid and cut off the oxygen supply. Ideal for flammable fuels (such as petrol) and solvent fires
• CO2 extinguishers: These displace the oxygen, smothering the fire without leaving any residue. Best for electrical fires involving flammable liquids
• ABC / Dry powder extinguishers: Versatile across multiple types of fire, including Class A, B and C; the powder works by interrupting the chemical reaction of fire.

Here is a handy chart for reference in terms of which extinguishers can be used for Class B fires:

Extinguisher Type	Suitable for Class B fires?	Explanation
Foam	Yes	Smothers the surface of liquid fires
CO2	Yes	Ideal for electrical equipment and flammable liquids
Dry Powder	Yes	Multi-purpose extinguishers suitable for automotive and industrial environments
Water	No	It can exacerbate the fire. Very dangerous with liquid fires.
Wet Chemical	No	Designed specifically for Class F (cooking oils) fires, NOT flammable liquids such as fuels
Lith-Ex	No	Effective ONLY against Lithium-ion battery fires and some Class A fires

Always remember that using the wrong extinguisher for the type of fire can make the situation worse. If you’re unsure of the type of fire or the extinguisher to use, do not attempt to tackle it yourself.

When it comes to fighting these types of fires, look for fire extinguishers with a Class B rating, as these are tested and approved for flammable liquid fires.

In addition to our foam, dry powder and CO2 fire extinguishers for use on Class B fires, the Firechief® range of fire safety products also includes extinguisher stands, suppression systems, signage and fire safety products for all types of fires. For information, call us on +44 (0)330 999 0019 or email sales@firechiefglobal.com.

To stay up-to-date with more product news and insights from across the fire safety industry, follow Firechief® Global on LinkedIn.

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Disclaimer

The information contained within this blog is provided solely for general informational and educational purposes and is not intended as a substitute for professional advice. Before taking any actions based upon this information, we advise the reader to consult all relevant statutory or regulatory guidance and, where necessary, to consult a qualified fire or industry regulation professional. The use or reliance on any information contained herein is solely at the reader's risk.