Fire Extinguisher Types Explained: Which One to Use and When
There are five main types of fire extinguisher — water, foam, CO2, dry powder and wet chemical — and using the wrong one can turn a manageable fire into a dangerous inferno. This guide explains every fire extinguisher type, the fire classes each covers, and exactly when each should — and should not — be used.
Important: Fire extinguishers are a last resort for small, contained fires only. If a fire is growing, spreading or generating significant smoke, evacuate immediately and call 999. Never put your safety at risk to tackle a fire.
Understanding Fire Classes
Fires are classified by the type of material burning. Different extinguishing agents work on different classes — using the wrong one can be ineffective or actively dangerous.
Solid materials — wood, paper, textiles, plastics, cardboard
Flammable liquids — petrol, oil, paint, solvents, alcohol
Flammable gases — LPG, propane, butane, natural gas
Metal fires — magnesium, aluminium, titanium, lithium
Cooking oils and fats — deep fat fryers, commercial kitchens
Fires involving live electrical equipment (not an official class but a key category)
Fire Extinguisher Types: Complete Guide
Water Extinguisher
Label colour: Red | Covers: Class A only
Suitable for:
- Wood, paper, textiles, cardboard
- General office materials
- Furniture and soft furnishings
Do NOT use on:
- Electrical fires
- Flammable liquids (Class B)
- Cooking oils (Class F)
- Metal fires (Class D)
The most common type. Ideal for offices, schools and shops. Never use on live electrical equipment — water conducts electricity. Some modern water extinguishers have additives that improve coverage on Class A fires at lower volumes.
Foam (AFFF) Extinguisher
Label colour: Cream | Covers: Class A and Class B
Suitable for:
- Wood, paper, textiles (Class A)
- Flammable liquids: petrol, paint, solvents (Class B)
- General commercial and industrial use
Do NOT use on:
- Electrical fires (unless labelled safe to 35kV)
- Cooking oils (Class F)
- Metal fires (Class D)
A versatile all-rounder. Forms a blanket over liquid fires, starving them of oxygen. Modern AFFF (Aqueous Film Forming Foam) extinguishers have largely replaced older foam types. Many are now rated for limited electrical use — always check the label.
Carbon Dioxide (CO2) Extinguisher
Label colour: Black | Covers: Class B and electrical fires
Suitable for:
- Electrical fires and live equipment
- Flammable liquids: petrol, solvents, oil (Class B)
- Server rooms, data centres, offices with electrical equipment
Do NOT use on:
- Class A fires — wood, paper, textiles (not effective)
- Cooking oils (Class F)
- Metal fires (Class D)
- Enclosed spaces (risk of asphyxiation)
The standard choice for offices and anywhere electrical equipment is present. CO2 does not leave residue, making it safe for use on sensitive equipment. Discharge is extremely cold — do not hold the horn during use. Provides no cooling effect so Class A fires can re-ignite.
Dry Powder (ABC) Extinguisher
Label colour: Blue | Covers: Class A, B and C
Suitable for:
- Flammable liquids (Class B)
- Flammable gases: LPG, butane, propane (Class C)
- Vehicle fires
- Outdoor and industrial environments
Do NOT use on:
- Indoor use in enclosed spaces — powder creates a dangerous cloud reducing visibility
- Sensitive electrical or electronic equipment (leaves residue)
- Cooking oils (Class F)
Extremely effective but messy. The powder causes significant secondary damage to equipment and environments. Not recommended for indoor use in occupied buildings. More commonly found in vehicles, plant rooms and industrial settings. A specialist dry powder (Class D) is available for metal fires.
Wet Chemical Extinguisher
Label colour: Yellow / Canary Yellow | Covers: Class F (and Class A)
Suitable for:
- Cooking oils and deep fat fryers (Class F)
- Commercial kitchens
- Catering environments
Do NOT use on:
- Electrical fires
- Flammable liquids (Class B)
- Flammable gases (Class C)
The only safe choice for Class F fires involving cooking oils. Wet chemical creates a soapy layer on the surface of burning oil that cools and smothers the fire. Never use water, CO2 or foam on a cooking oil fire — the result can be a violent explosion of burning oil. Mandatory in commercial kitchens under BS 5306.
Are Your Extinguishers Correctly Specified and Maintained?
Fyrup provides fire extinguisher supply, installation and annual servicing across London.
Quick Reference: Which Extinguisher for Which Fire?
| Fire Type | Water (Red) | Foam (Cream) | CO2 (Black) | Powder (Blue) | Wet Chem (Yellow) |
|---|---|---|---|---|---|
| Class A — Wood/Paper | ✓ | ✓ | ✗ | ✓ | ✓ |
| Class B — Flammable Liquids | ✗ | ✓ | ✓ | ✓ | ✗ |
| Class C — Flammable Gases | ✗ | ✗ | ✗ | ✓ | ✗ |
| Electrical | ✗ | Check label | ✓ | ✓ | ✗ |
| Class F — Cooking Oils | ✗ | ✗ | ✗ | ✗ | ✓ |
Legal Requirements for Fire Extinguishers
Under the Regulatory Reform (Fire Safety) Order 2005, the responsible person for any non-domestic premises is required to provide appropriate firefighting equipment and ensure it is maintained. In practice, this means:
- Extinguishers must be appropriate for the fire risks present in the building
- They must be positioned in accessible locations and clearly signposted
- Annual service inspections must be carried out by a competent person
- Monthly visual checks should be recorded in a fire log book
- Extinguishers must be replaced or professionally serviced after use
Do Not Use Water or Foam on a Chip Pan or Deep Fat Fryer
Pouring water onto burning cooking oil causes a violent steam explosion, propelling burning oil across the room. This is one of the most common causes of serious kitchen fires. The only safe response to a cooking oil fire is a wet chemical extinguisher — or a fire blanket to smother a small pan fire. If in doubt, evacuate.
How Many Extinguishers Do You Need?
BS 5306-8:2012 (the standard for selection and installation of portable fire extinguishers) provides guidance on the number and type of extinguishers required based on floor area and risk category. As a general guide:
Minimum provision
At least one Class A extinguisher (water or foam) for every 200m² of floor area, with a minimum of two per floor.
Travel distance
No person should have to travel more than 30 metres to reach a Class A extinguisher.
Placement
Extinguishers should be wall-mounted on brackets or floor-stand units, positioned near fire exits and at fire points.
Additional provision
Kitchen, plant room and electrical room risks require additional extinguishers appropriate to the specific hazard.
Get Your Fire Extinguishers Professionally Serviced
Fyrup supplies, installs and carries out annual servicing of fire extinguishers to BS 5306 across London. We ensure you have the right equipment, in the right place, fully maintained.
Frequently Asked Questions
How many types of fire extinguisher are there?
There are five main types of fire extinguisher used in the UK: water (red), foam (cream), CO2 (black), dry powder (blue) and wet chemical (yellow). Each is colour-coded by a band on the body and is designed for specific classes of fire. A specialist dry powder type is also available for Class D metal fires.
Which fire extinguisher should I use on an electrical fire?
Use a CO2 (black) extinguisher on fires involving live electrical equipment. CO2 leaves no residue, making it safe for computers, servers and electronics. Never use a water or standard foam extinguisher on a live electrical fire, as water conducts electricity. Some foam extinguishers are dielectrically tested for limited electrical use — always check the label.
What fire extinguisher do you use for a cooking oil or chip pan fire?
Only a wet chemical (yellow) extinguisher should be used on a Class F fire involving cooking oils and fats, such as a deep fat fryer or chip pan. It creates a soapy layer that cools and seals the burning oil. Never use water, foam or CO2 on a cooking oil fire — it can cause a violent explosion of burning oil. A fire blanket can smother a small pan fire.
Which fire extinguisher is used for flammable liquids?
Flammable liquids such as petrol, paint, oil and solvents are Class B fires. Use a foam (cream) or dry powder (blue) extinguisher. Foam forms a blanket over the liquid to starve it of oxygen; dry powder smothers the flames. CO2 can also be effective on small Class B fires. Water must never be used as it spreads the burning liquid.
What size fire extinguisher do I need?
Extinguisher size is rated by its fire rating, not just its weight. For most offices, a 6-litre foam or 2kg CO2 extinguisher is standard. BS 5306-8 requires a minimum of two Class A extinguishers per floor and at least 26A of Class A fire-fighting capability per floor, with no one travelling more than 30 metres to reach one. A fire risk assessment confirms the exact provision for your premises.
What is a Class F fire?
A Class F fire involves cooking oils and fats, typically in commercial kitchens, deep fat fryers and catering equipment. These fires burn at very high temperatures and cannot be safely extinguished with water, foam or CO2. The only suitable extinguisher is a wet chemical (yellow) type, supported by a fire blanket for small pan fires.
How often do fire extinguishers need to be serviced?
Fire extinguishers must be serviced annually by a competent person under BS 5306-3, with the responsible person carrying out monthly visual checks recorded in a fire log book. Extended (discharge) servicing is required every 5 years for most types and every 10 years for CO2 extinguishers. Any extinguisher that has been used must be recharged or replaced immediately.