Guide to Fire Classes and Suitable Fire Extinguishers

Knowing the different classes of fire is an important part of fire safety. Not every fire extinguisher can be used on every type of fire, and using the wrong one can make the situation more dangerous and increase the risk of injury.

This guide explains the main fire classes, where they are commonly found, and which fire extinguishers are appropriate for each type.

The Main Classes of Fire

There are six recognised classes of fire:

• Class A – Solid combustible materials
  
• Class B – Flammable liquids
  
• Class C – Flammable gases
  
• Class D – Combustible metals
  
• Electrical fires
  
• Class F – Cooking oils and fats
  

The Regulatory Reform (Fire Safety) Order 2005 requires businesses and premises to provide suitable fire safety equipment based on the risks present within the building. Carrying out a fire risk assessment helps identify potential hazards and ensures the correct extinguishers are available.

Different workplaces and environments face different fire risks, so understanding the fire classes is essential when selecting fire safety equipment.

Fire Classes Explained

Class A – Solid Combustible Materials

Class A fires involve common combustible materials such as:

• Wood
  
• Paper
  
• Cardboard
  
• Fabrics
  
• Plastics
  

These fires are often caused when heat or naked flames come into contact with solid materials that burn easily.

Common Locations

• Offices
  
• Schools
  
• Warehouses
  
• Hospitals
  
• Shops
  

Suitable Fire Extinguishers

• Water
  
• Foam
  
• Powder
  
• Wet chemical
  
• Water mist
  

Class B – Flammable Liquids

Class B fires are caused by flammable liquids including:

• Petrol
  
• Diesel
  
• Paints
  
• Solvents
  
• Spirits
  

These substances can ignite quickly and spread fire rapidly.

Common Locations

• Garages
  
• Laboratories
  
• Construction sites
  
• Restaurants and bars
  
• Petrol stations
  

Suitable Fire Extinguishers

• Foam
  
• CO2
  
• Powder
  

Class C – Flammable Gases

Class C fires involve gases such as:

• Propane
  
• Butane
  
• Methane
  

Because these gases are highly flammable, they must be stored and handled carefully.

Common Locations

• Industrial facilities
  
• Manufacturing plants
  
• Chemical storage areas
  

Suitable Fire Extinguishers

• Powder extinguishers only
  

Class D – Metal Fires

Class D fires occur when combustible metals ignite. Examples include:

• Lithium
  
• Magnesium
  
• Sodium
  

Metal fires can react violently with water and burn at extremely high temperatures.

Common Locations

• Laboratories
  
• Engineering workshops
  
• Metal processing facilities
  

Suitable Fire Extinguishers

• Specialist powders, such as L2/M28 extinguishers
  

Electrical Fires

Electrical fires involve live electrical equipment or installations.

Water-based extinguishers should never be used on electrical fires because water conducts electricity and may cause electrocution.

Common Locations

• Offices
  
• Plant rooms
  
• Workshops
  
• Server rooms
  

Suitable Fire Extinguishers

• CO2 extinguishers
  
• Powder extinguishers

Class F – Cooking Oils and Fats

Class F fires involve cooking oils and fats used in kitchens and catering environments.

These fires can become extremely dangerous if water is applied, as it may cause the burning oil to spread violently.

Common Locations

• Commercial kitchens
  
• Restaurants
  
• Cafes
  
• Catering businesses
  

Suitable Fire Extinguishers

• Wet chemical
  
• Water mist