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Classes of fire extinguishers: What should I know about the different classes of fire extinguishers?

Understanding the classes of fire extinguishers

Fire classification groups fires by fuel type. Knowing these classes helps you pick the right extinguisher and avoid actions that make a fire worse. The main UK‑recognised fire classes are A, B, C, D and K. Each class needs a compatible extinguishing medium. For example, water‑based extinguishers cool Class A fires but will spread Class B liquid fires and may cause electrocution on live electrical equipment. Use an extinguisher rated for the fire class you face. knowledge.bsigroup.com

Which extinguisher for which fire class?

Class A (solids): Paper, wood, textiles and many plastics. Use water, water‑mist or foam extinguishers that cool and soak the burning fuel.

Class B (liquids): Petrol, oils, solvents and some paints. Use foam, carbon dioxide (CO2) or specialist dry powder extinguishers that smother or displace oxygen.

Class C (electrical): Energised electrical equipment. Use CO2 or clean dry chemical extinguishers; do not use water. If the equipment can be isolated safely, a Class A extinguisher may then be used.

Class D (metals): Combustible metals such as magnesium, sodium or titanium. Use special metal‑powder extinguishers formulated for the specific metal. Incorrect agents can produce violent reactions.

Class K (kitchen fats and oils): Deep fat and cooking oil fires. Use wet chemical extinguishers that saponify and cool the fuel.

Bear in mind that some extinguishers carry multiple ratings (for example A B C) and can be used across several classes. However, multi‑purpose does not mean universal. Always check the label and only use the agent for the classes shown. knowledge.bsigroup.com

How extinguishers are labelled, colour coded and rated

Modern UK extinguishers show class symbols and may include a performance number. The letter indicates the class; the number before A or B gives a measure of effectiveness (higher is better). In addition, the traditional coloured band that once identified the extinguishing medium is now a small band on new appliances, with the red body retained for visibility. British Standards and guidance explain selection, positioning and labelling in detail. Follow that guidance when planning coverage for your premises. shop-checkout.bsigroup.com

Special considerations: kitchens, lithium batteries and metal fires

Commercial kitchens need wet chemical extinguishers rated for cooking oils and fats; these are typically mandatory where deep fat fryers are used. For electrical and battery fires, CO2 or clean agents avoid conductive residues. Lithium‑ion battery fires are becoming more common and may need special extinguishers and procedures because they can reignite; consult a competent fire safety adviser. For combustible metal risks, only use class D powder specifically designed for the metal type and ensure staff have specialist training. In all these situations, a site‑specific fire risk assessment will identify the right appliances. nfcc.org.uk

Under the Regulatory Reform (Fire Safety) Order 2005 the “responsible person” must provide appropriate firefighting equipment and maintain it in good working order. That duty applies to most non‑domestic premises and means you must assess risk and make equipment choices based on that assessment. British Standards such as BS 5306 set out recommended practice for selecting, siting and maintaining portable extinguishers. For these reasons, you should record decisions and keep evidence of maintenance and servicing to demonstrate compliance. gov.uk

Maintenance, inspection and servicing: what you must do

You should carry out monthly visual checks and arrange an annual professional service by a competent, certified technician. Additionally, extinguishers require deeper maintenance at specific intervals (for example mass checks, six‑year internal checks and hydrostatic testing at prescribed years depending on the type). These intervals and the tasks to be completed are described in BS 5306 and trusted industry guidance. If an extinguisher has been used, it must be recharged or replaced immediately. Keep service records, tags and a logbook for every appliance. totalsafeuk.com

If you prefer, Total Safe can carry out a full audit and annual servicing to keep appliances compliant and documented; we also offer advice on replacement, labelling and disposal. See Total Safe fire safety services. totalsafeuk.com

Recent regulatory change affecting foam extinguishers

Regulation of firefighting foams has changed in recent years. In particular, restrictions on foams containing PFOA (a PFAS compound) mean that certain AFFF foams were banned from use from 4 July 2025. As a result, duty holders should check foam extinguishers and suppression systems for legacy PFOA content and plan safe disposal or replacement where necessary. Many manufacturers have switched to compliant alternatives, but you must verify the composition of older appliances. Total Safe can help identify affected units and recommend compliant replacements. britsafe.org

Where to position extinguishers and how many you need

Placement follows the hazards identified in your fire risk assessment. Extinguishers must be visible, accessible and sited along escape routes where possible. Keep travel distances within the guidance in BS 5306‑8 and place specialist appliances near the specific risks they serve (for example wet chemical near cooking equipment). Avoid obstructing appliances and ensure signage is clear. If you need help sizing or siting equipment, request a site visit and audit from a competent provider. Total Safe fire extinguisher servicing and siting advice. knowledge.bsigroup.com

Training and safe use: what staff must know

Extinguishers are effective only when used safely. Train nominated staff in extinguisher selection, safe approach to a small fire, the PASS technique (Pull, Aim, Squeeze, Sweep), and the decision‑to‑retreat if the fire grows or smoke increases. Importantly, staff should never put themselves at risk. NFCC resources and local fire and rescue services offer guidance and awareness tools to support training and competence. Combine theory with practical, supervised exercises for confidence. nfcc.org.uk

Choosing a supplier and verifying competence

Use a BAFE SP101‑registered or similarly accredited supplier for servicing and commissioning. Such organisations follow BS 5306 and can provide trained engineers, clear records and valid certificates. Verify competence, ask to see accreditations, and request written evidence of service work and any replacement parts. This protects your occupants and provides the documentary trail required by enforcement bodies and insurers. bafe.org.uk

Practical checklist for responsible persons

Review your fire risk assessment. Carry out or review your fire risk assessment and record the outcomes.

Verify extinguisher suitability. Verify that extinguishers on site are the right class for identified hazards.

Complete monthly checks. Ensure monthly visual checks are completed and logged.

Arrange annual servicing. Book annual professional servicing with a BAFE/BSI‑competent provider.

Replace PFOA foams. Replace or dispose of legacy PFOA AFFF foams where required and obtain hazardous waste consignment notes.

Train staff. Arrange staff training and maintain evidence of completion.

These steps reduce risk, help with compliance and protect your insurance position. For a site audit and tailored recommendations, contact Total Safe for a free consultation. Arrange a Total Safe fire safety audit. totalsafeuk.com

Conclusion and next steps

The classes of fire extinguishers link directly to the types of fuel and the correct extinguishing method. Use the right appliance for the right class, keep equipment maintained, and ensure staff receive training. Follow British Standards and the duties set out in the Regulatory Reform (Fire Safety) Order to reduce risk and demonstrate compliance. If you are unsure about the correct selection, siting or condition of extinguishers at your site, book a professional fire safety audit and annual servicing with Total Safe. Proper planning and timely maintenance make extinguishers reliable first‑response tools and keep people safer.

External guidance referenced: Regulatory Reform (Fire Safety) Order 2005 guidance, BS 5306 selection and positioning guidance (BSI), and NFCC Business Fire Safety Awareness Tool. gov.uk

FAQ

Q: How often should fire extinguishers be serviced professionally?

A: Arrange a professional service at least once every 12 months; carry out monthly visual checks in between services. totalsafeuk.com

Q: Can one extinguisher cover A, B and C fires?

A: Multi‑purpose ABC extinguishers cover many common workplace fires, but you must still match appliances to specific hazards such as kitchen oil (Class K) and metal fires (Class D). knowledge.bsigroup.com

Q: Are older foam extinguishers still legal after July 2025?

A: Extinguishers containing PFOA were banned from use from 4 July 2025; duty holders should verify foam composition and replace or dispose of affected units in line with guidance. britsafe.org

Q: Who is responsible for choosing and maintaining extinguishers?

A: The “responsible person” under the Regulatory Reform (Fire Safety) Order must ensure appropriate equipment is provided, maintained and recorded. Seek a competent adviser where needed. gov.uk

Q: Where can I get authoritative guidance on standards and siting?

A: British Standards Institution publications such as BS 5306 provide selection and positioning guidance, and industry bodies like BAFE offer practical service and competence criteria. knowledge.bsigroup.com

If you would like a site survey, extinguisher audit or staff training, contact Total Safe and we will provide a clear plan to make your extinguishers fit for purpose and fully compliant. Arrange a Total Safe fire safety audit