Fire class · UK/EU and US
Class B: flammable liquids
First: raise the alarm, get out, call the fire service
UK: However, if in doubt, employees should not put themselves or anyone else at risk, but simply raise the alarm, leave the premises, and call the fire and rescue service.
HM Government (GOV.UK), A guide to making your small non-domestic premises safe from fire (accessible version), section ‘Fire extinguishers’
US: If you're unsure about whether it is safe to use a fire extinguisher, and for all other situations, alert others, leave the building, and call 911 from a mobile or neighbor's phone.
US Fire Administration (FEMA), Choosing and Using Fire Extinguishers, ‘Help people decide when to use a fire extinguisher’
Flammable liquids: petrol, diesel, oils.
UK and Europe (BS EN 2 classes)
Fires involving flammable liquids such as petrol, diesel or oils.
HM Government (GOV.UK), Fire safety risk assessment: offices and shops (accessible version), Part 2, 3.1, Table 1: Class of fireCLASS B: Fires involving liquids or liquefiable solids, e.g. petrol, diesel or oils.
London Fire Brigade (London Fire Commissioner), Fire Safety Guidance Note GN08: Hand Held Portable Firefighting Equipment, Rev 20, §3.2 (after BS EN 2)
United States (NFPA 10 classes)
Fires in flammable liquids, combustible liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols, and flammable gases.
National Fire Protection Association (NFPA), Fire Extinguisher Ratings (NFPA Today blog, Brian O’Connor), table of classes
Extinguishers the guidance names for Class B
Extinguishers the guidance says not to use on it
- Water:
Do not use on liquid, electrical or metal fires.
HM Government (GOV.UK), Fire safety risk assessment: offices and shops (accessible version), Part 1, 3.4.2, Figure 8 (water) - Water:
It should not be used for kitchen fires, fires caused by flammable gas and liquids as well as fires that involve electrical equipment.
Surrey County Council (Surrey Fire and Rescue Service), Extinguishers and fire blankets, ‘Water Extinguishers’ - Water:
Never use water to extinguish flammable liquid fires.
US Occupational Safety and Health Administration (OSHA), eTool: Evacuation Plans and Procedures, Portable Fire Extinguishers, Extinguisher Basics, Water (APW) extinguishers - Wet chemical:
Also keep in mind that if a Class K fire extinguisher is installed, there still needs to be extinguisher(s) available for any other combustible materials in the area since oftentimes a Class K extinguisher can’t be used on an ordinary combustibles fire, flammable liquids fire, electrical fire, or combustible metals fire.
National Fire Protection Association (NFPA), What Is a Class K Fire Extinguisher? (NFPA Today blog, Brian O’Connor), ‘Where should I install Class K fire extinguishers?’
Reading the letter
- The US Class B includes flammable gases. The UK and European system gives gases their own letter, C.
CLASS B: … Types include Foam extinguisher, CO² extinguisher, Dry powder extinguisher (size according to risk).
London Fire Brigade (London Fire Commissioner), Fire Safety Guidance Note GN08: Hand Held Portable Firefighting Equipment, Rev 20, §3.2A 2.5 kilogram Carbon Dioxide (CO²) extinguisher is rated as a 34B.
London Fire Brigade (London Fire Commissioner), Fire Safety Guidance Note GN08: Hand Held Portable Firefighting Equipment, Rev 20, §5.2The number 10 indicates it can extinguish Class B fires up to 10 square feet in size, and the C indicates that it can be used for Class C fires.
US Fire Administration (FEMA), Choosing and Using Fire Extinguishers, ‘How to read the classification label’ (for a 1A:10B:C label)
Other fire classes
Sources
Official guidance only: UK government, UK fire and rescue services, the Fire Industry Association, NFPA, OSHA and the US Fire Administration. Words in quotation marks are theirs.
- HM Government (GOV.UK): Fire safety risk assessment: offices and shops (accessible version) (updated 12 September 2023). Quoted here: Part 2, 3.1, Table 1: Class of fire; Part 1, 3.4.2, Figure 8 (water). www.gov.uk Checked 2026-09-29.
- London Fire Brigade (London Fire Commissioner): Fire Safety Guidance Note GN08: Hand Held Portable Firefighting Equipment, Rev 20 (January 2025). Quoted here: §3.2 (after BS EN 2); §3.2; §5.2. www.london-fire.gov.uk Checked 2026-09-29.
- National Fire Protection Association (NFPA): Fire Extinguisher Ratings (NFPA Today blog, Brian O’Connor) (26 August 2022). Quoted here: table of classes. www.nfpa.org Checked 2026-09-29.
- HM Government (GOV.UK): A guide to making your small non-domestic premises safe from fire (accessible version) (updated 20 January 2025). Quoted here: section ‘Fire extinguishers’. www.gov.uk Checked 2026-09-29.
- US Fire Administration (FEMA): Choosing and Using Fire Extinguishers (page last reviewed 1 April 2023). Quoted here: ‘Help people decide when to use a fire extinguisher’; ‘How to read the classification label’ (for a 1A:10B:C label). www.usfa.fema.gov Checked 2026-09-29.
- Surrey County Council (Surrey Fire and Rescue Service): Extinguishers and fire blankets (reviewed 24 August 2026). Quoted here: ‘Water Extinguishers’. www.surreycc.gov.uk Checked 2026-09-29.
- US Occupational Safety and Health Administration (OSHA): eTool: Evacuation Plans and Procedures, Portable Fire Extinguishers, Extinguisher Basics (no date shown). Quoted here: Water (APW) extinguishers. www.osha.gov Checked 2026-09-29.
- National Fire Protection Association (NFPA): What Is a Class K Fire Extinguisher? (NFPA Today blog, Brian O’Connor) (12 August 2024). Quoted here: ‘Where should I install Class K fire extinguishers?’. www.nfpa.org Checked 2026-09-29.