A detailed reference for responsible persons, building managers, engineers, and organisations — covering fire classes, extinguisher types, suitability, placement, and maintenance to BS 5306-3.
Using the wrong type of fire extinguisher can make a fire significantly worse, cause electric shock, or spread burning liquid. This guide explains the UK fire classes, each extinguisher type, which fires they are suitable for, where they should be placed, and how they must be maintained. It is written for responsible persons, building managers, engineers, and organisations who need to understand and comply with the Regulatory Reform (Fire Safety) Order 2005 and BS 5306-3.
Fires are classified by the fuel involved. The class of fire determines which extinguisher is safe and effective to use. Always isolate electrical supplies before fighting an electrical fire.
Fires involving solid materials such as wood, paper, textiles, coal, and certain plastics.
Common in: Offices, homes, warehouses
Fires involving petrol, diesel, oil, paint, solvents, and other liquid fuels.
Common in: Garages, kitchens, workshops
Fires involving flammable gases such as propane, butane, methane, and hydrogen.
Common in: Laboratories, industrial sites
Fires involving combustible metals such as magnesium, titanium, sodium, and potassium.
Common in: Manufacturing, metal workshops
Fires involving cooking oils and fats at high temperature in kitchen appliances.
Common in: Commercial kitchens, restaurants
Fires involving electrical equipment and installations (not a separate class in the UK, treated as A, B, or C once the supply is isolated).
Common in: All premises
Use this matrix to identify which extinguisher is suitable for each fire type. Always read the extinguisher label and confirm compatibility before use.
| Fire Type | Water | Foam | CO₂ | Dry Powder | Wet Chemical | Water Mist |
|---|---|---|---|---|---|---|
| Class A (Solids) | ||||||
| Class B (Liquids) | ||||||
| Class C (Gases) | ||||||
| Class D (Metals) | ||||||
| Class F (Cooking Oils) | ||||||
| Electrical |
Every extinguisher in the UK is colour-coded red with a coloured label identifying the contents. The details below cover each type, its suitability, capacity, fire rating, and the environments it is best suited to.
Label: Red
The most common extinguisher for solid combustible fires. Cools the burning material below its ignition temperature, removing the heat element of the fire triangle. Never use on electrical, liquid, or cooking-oil fires — it can spread the fire or cause electric shock.
Effective on:
Best for:
Not suitable for:
Label: Red / Cream label
Forms a smothering foam blanket over flammable liquids, preventing vapour release and cutting off oxygen. Also effective on solid combustible materials. Suitable for many commercial and industrial risks where both solid and liquid fuels are present.
Effective on:
Best for:
Not suitable for:
Label: Red / Black label
Displaces oxygen and cools the fire with a discharge of carbon dioxide gas. Leaves no residue — ideal for protecting electrical equipment, switchgear, and sensitive electronics. Limited reach and discharge time; ineffective on solid combustibles.
Effective on:
Best for:
Not suitable for:
Label: Red / Blue label
A multi-purpose extinguisher that knocks down flames by chemically interrupting the combustion reaction. Highly effective on gas, liquid, and electrical fires. Not recommended for indoor use except where specified — the powder severely reduces visibility and is difficult to clean up.
Effective on:
Best for:
Not suitable for:
Label: Red / Yellow label
Specifically designed for Class F fires involving cooking oils and fats. Creates a cooling mist and a chemical reaction (saponification) that forms a foam blanket over the burning oil, suppressing flames and preventing re-ignition. Also effective on Class A fires.
Effective on:
Best for:
Not suitable for:
Label: Red / White label
Uses ultra-fine water mist to suppress fires through cooling and oxygen displacement. Environmentally friendly with minimal water residue. Safe for use on electrical equipment due to the de-ionised water and fine droplet size. Versatile across multiple fire types.
Effective on:
Best for:
Not suitable for:
Correct placement ensures extinguishers can be reached quickly in an emergency. BS 5306-8 gives guidance on the selection and positioning of portable fire extinguishers.
Position extinguishers near final exit doors so they can be reached quickly and used on the way out.
Place on escape routes so they are visible and accessible without travelling into a fire area.
Locate close to the specific risk (kitchen, plant room, electrical switchgear) but not so close that the fire prevents access.
Carry handle should be approximately 1.0m to 1.2m from floor level. Heavier units (9L+) lower, lighter units higher.
No one should need to travel more than 30m to reach an extinguisher. Reduce to 15m in higher-risk areas.
Each extinguisher must have an ID sign immediately above it identifying its type and the fires it is suitable for (BS EN ISO 7010).
Portable fire extinguishers are a critical first-line of defence against fire — but only when they are properly commissioned and regularly maintained by a competent company. Simply purchasing extinguishers and placing them on the wall is not enough. UK legislation and best practice require that all portable extinguishers are commissioned on installation and inspected at least annually by a qualified engineer.
Under BS 5306-3, all portable fire extinguishers must be commissioned by a competent person before they are placed into service. Commissioning is not just unpacking and mounting — it is a formal technical check that confirms the unit is correctly charged, the safety mechanisms are functioning, and the appliance is fit for purpose.
Commissioning by a competent company ensures:
Using an unqualified person to commission or service extinguishers is a risk to life and may invalidate your insurance and fire risk assessment.
A competent service engineer follows a defined procedure at every annual inspection. Each of the checks below is part of the BS 5306-3 service routine.
Anti-tamper tags and pull-pin seals provide visible evidence that a unit has not been discharged or tampered with since its last inspection.
A missing or broken tag should always be investigated — it may indicate the extinguisher has been used, discharged, or interfered with.
O-rings form a critical pressure seal within the extinguisher. Over time, they can dry out, crack, or deteriorate — leading to slow pressure loss or sudden failure.
Failing to replace worn O-rings is one of the most common causes of extinguisher failure on discharge.
All extinguishers — especially CO₂ and stored-pressure types — must be weighed at every annual inspection and the result recorded.
The engineer must:
The cylinder is a pressure vessel. Any physical damage or corrosion reduces its structural integrity and creates a risk of catastrophic failure on discharge.
Any extinguisher showing significant damage, deep corrosion, or a compromised hose must be removed from service and either repaired by a competent engineer or condemned and replaced.
For stored-pressure extinguishers (water, foam, powder, wet chemical), the pressure gauge must be checked at every inspection.
CO₂ extinguishers do not have a pressure gauge — weight is the only reliable indicator of charge level.
An extinguisher is useless if it cannot be reached or found quickly in an emergency. The engineer must verify its placement.
If the location has changed or the extinguisher is now obscured, the engineer should advise the responsible person and update the fire safety records.
Where extinguishers are fitted with a hose (powder, CO₂, foam, wet chemical), the hose must be removed and visually inspected during the annual service.
A blocked or cracked hose will prevent effective discharge when the unit is needed most.
The operating instructions on the label must be clearly legible and facing outward. In an emergency, the user may need to read the label quickly.
Extinguishers with illegible or missing labels should have replacement labels fitted or, if this is not possible, the unit should be replaced.
Dry powder extinguishers are particularly prone to powder compaction and caking, where the powder settles into a solid mass that prevents effective discharge.
This step is critical for powder extinguishers stored in areas of vibration (near machinery or vehicles), areas of high humidity, or units that have been in service for several years.
Every inspection — whether a commissioning visit, annual service, or interim check — must be formally documented.
The responsible person should retain all service records as part of their fire safety documentation. These records are required by BS 5306-3 and may be inspected by the fire authority.
BS 5306-3 requires that all portable fire extinguishers in service are inspected and maintained at least once every 12 months by a competent person. This is not optional.
In addition to the annual professional service, the responsible person should carry out monthly visual checks — confirming that extinguishers are in place, undamaged, and accessible.
CO₂ extinguishers are subject to specific pressure vessel legislation under the Pressure Equipment (Safety) Regulations 2016 (PESR) and the Pressure Systems Safety Regulations 2000 (PSSR).
Because CO₂ cylinders are high-pressure vessels (charged to around 50-60 bar), they must undergo a hydraulic pressure test — commonly called a stretch test or extended life test — every 10 years from the date of manufacture.
The stretch test involves:
Key points for responsible persons:
The responsible person must ensure all extinguishers are maintained in efficient working order. Records of all inspections and services must be kept in the fire safety logbook.
Performed by: Responsible person
Check the extinguisher is in place, accessible, undamaged, and the pressure gauge (if fitted) is in the green zone. Record the check in the fire safety logbook.
Performed by: Competent service engineer
BS 5306-3 annual service by a competent person. Verify weight, pressure, condition, and replace seals. Service label applied.
Performed by: Competent service engineer
Every 5 years (or 10 years for some CO₂ units). Discharge test, internal inspection, refill or replace.
Performed by: Competent service engineer
Replace at end of life — typically 10-20 years depending on type, condition, and manufacturer guidance. CO₂ units subject to hydraulic pressure testing.
Under the Regulatory Reform (Fire Safety) Order 2005 the responsible person must ensure appropriate extinguishers are provided, maintained, and that staff are trained in their safe use.
BS 5306-3:2023
Fire extinguishing installations and equipment. Commissioning and maintenance of portable fire extinguishers.
BS 5306-8:2012
Selection and positioning of portable fire extinguishers. Code of practice.
BS EN 3-7
Portable fire extinguishers — characteristics, performance, and test methods.
BS EN ISO 7010
Graphical symbols — registered safety signs, including fire extinguisher ID signs.
RRFSO 2005
Regulatory Reform (Fire Safety) Order 2005 — legal duty to provide and maintain firefighting equipment.
BS 9999:2017
Fire safety in the design, management and use of buildings — includes extinguisher provision guidance.
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