Fire safety is a crucial aspect of protecting homes, businesses, and public spaces. In the UK, fires are categorised into five different classes, each based on the type of material burning. Understanding these fire classes is essential for choosing the correct fire extinguisher, ensuring compliance with UK fire safety regulations, and preventing unnecessary damage or injury.
In this blog, we will explain the five fire classes, how they behave, and the best ways to extinguish them according to British Standards (BS EN 3-7).
The Five Classes of Fires in the UK
The BS EN 3-7 standard defines fire classifications and fire extinguisher types in the UK. Fires are categorised as Class A, B, C, D, and F, each requiring a specific approach to extinguishing them safely.
| Fire Class | Type of Material Burning | Common Examples | Best Extinguishing Method |
|---|---|---|---|
| Class A | Solid combustible materials | Wood, paper, textiles, plastics | Water, foam, dry powder |
| Class B | Flammable liquids | Petrol, diesel, oil-based paints | Foam, CO₂, dry powder |
| Class C | Flammable gases | Propane, butane, methane | Dry powder (only if safe to stop the gas leak) |
| Class D | Flammable metals | Magnesium, lithium, aluminium dust | Specialist dry powder |
| Class F | Cooking oils and fats | Deep-fat fryers, frying pans | Wet chemical extinguishers |
Class A Fires: Solid Combustible Materials
What Are Class A Fires?
Class A fires involve solid organic materials such as wood, paper, textiles, and plastics. These are among the most common types of fires and can spread quickly if not controlled.
How to Extinguish a Class A Fire
- Water Extinguishers: The most effective method, as water cools the burning material and prevents reignition.
- Foam Extinguishers: Work well by smothering flames and cooling the material.
- Dry Powder Extinguishers: Can be used but are less effective than water or foam for deep-seated fires.
Where Are Class A Fires Most Common?
- Homes and offices (paper, furniture, carpets).
- Warehouses (cardboard, packaging materials).
- Schools and public buildings (wooden structures, textiles).
Class B Fires: Flammable Liquids
What Are Class B Fires?
Class B fires involve flammable liquids, including petrol, diesel, solvents, and oil-based paints. These fires can spread rapidly, particularly in confined spaces.
How to Extinguish a Class B Fire
- Foam Extinguishers: The best option, as they create a barrier that prevents the liquid from reigniting.
- CO₂ Extinguishers: Useful for small liquid fires, particularly near electrical equipment.
- Dry Powder Extinguishers: Can be used, but foam is preferred in most cases.
Never use water, as it can spread the liquid, worsening the fire.
Where Are Class B Fires Most Common?
- Petrol stations and garages.
- Factories and warehouses storing flammable liquids.
- Chemical storage facilities.
Class C Fires: Flammable Gases
What Are Class C Fires?
Class C fires involve flammable gases such as propane, butane, and methane. These fires are highly dangerous due to the risk of explosions.
How to Extinguish a Class C Fire
- Dry Powder Extinguishers: The only suitable extinguisher for gas fires.
- Shut Off the Gas Supply: If possible, stopping the gas flow is the safest way to control the fire.
Where Are Class C Fires Most Common?
- Gas storage and distribution facilities.
- Industrial sites using propane or butane.
- Commercial kitchens using gas cookers.
Important Note: If the gas supply cannot be stopped, evacuate the area and call emergency services rather than attempting to extinguish the fire.
Class D Fires: Flammable Metals
What Are Class D Fires?
Class D fires involve flammable metals, such as magnesium, lithium, sodium, and aluminium dust. These fires are common in manufacturing and laboratory environments.
How to Extinguish a Class D Fire
- Specialist Dry Powder Extinguishers: These contain metal-specific powders (e.g., graphite or sodium chloride) that smother flames without reacting with the metal.
- Never Use Water or CO₂: Water can cause flammable metals to explode, while CO₂ can react violently with some burning metals.
Where Are Class D Fires Most Common?
- Laboratories handling reactive metals.
- Metalworking and engineering plants.
- Battery manufacturing and recycling facilities.
Class F Fires: Cooking Oils and Fats
What Are Class F Fires?
Class F fires involve cooking oils and fats, such as those used in deep-fat fryers. These fires burn at extremely high temperatures, making them difficult to extinguish.
How to Extinguish a Class F Fire
- Wet Chemical Extinguishers: The only safe method, as they cool the oil and form a protective layer to prevent reignition.
- Fire Blankets: Can be used for small pan fires, but only if it fully covers the fire.
Never use water, as it can cause a violent reaction, sending burning oil into the air and worsening the fire.
Where Are Class F Fires Most Common?
- Commercial kitchens and restaurants.
- Homes with deep-fat fryers.
- Catering businesses and food trucks.
Choosing the Right Fire Extinguisher for Each Fire Class
Selecting the correct extinguisher is essential for fire safety compliance and ensuring quick and effective fire suppression.
| Fire Class | Best Extinguisher Type | Extinguisher Colour Code (UK) |
|---|---|---|
| Class A | Water, Foam, Dry Powder | Red (Water), Cream (Foam), Blue (Dry Powder) |
| Class B | Foam, CO₂, Dry Powder | Cream (Foam), Black (CO₂), Blue (Dry Powder) |
| Class C | Dry Powder (if gas supply is off) | Blue (Dry Powder) |
| Class D | Specialist Dry Powder | Blue (Specialist Powder) |
| Class F | Wet Chemical | Yellow (Wet Chemical) |
UK fire safety regulations, such as the Regulatory Reform (Fire Safety) Order 2005, require businesses to have appropriate fire extinguishers based on the specific fire risks in their premises. Regular fire risk assessments are necessary to determine the best protection.
Fire Classes and Safe Fire Extinguishing
Understanding the different fire classes and using the correct extinguishing method is crucial for fire safety. Using the wrong extinguisher can worsen a fire, cause injuries, or even trigger an explosion in some cases.
Key Fire Safety Tips
- Identify potential fire hazards in your home or workplace and ensure you have the correct extinguishers in place.
- Train employees or household members on how to use fire extinguishers safely.
- Conduct regular fire risk assessments to remain compliant with UK fire safety regulations.
- Ensure extinguishers are serviced annually by a qualified professional.
- If a fire becomes too large to control, evacuate immediately and call 999.
For expert advice on fire extinguishers, fire risk assessments, and compliance with UK fire safety laws, contact Martyn Young Fireproofing Consultancy today. Our specialists can help ensure your property is fully protected and legally compliant.