Definition
A CO2 (carbon dioxide) fire extinguisher is a portable firefighting device that discharges pressurised carbon dioxide gas to smother a fire by displacing oxygen. It leaves no residue, making it the preferred choice for electrical equipment, server rooms, and environments where contamination cannot be tolerated.
BFC Training
EAL Level 3 accredited training — the only nationally recognised qualification across all fire disciplines.
View training courseCarbon dioxide is stored as a liquid under pressure inside the extinguisher cylinder. When the operating lever is depressed, CO2 is released through a discharge horn, where it immediately expands and converts to gas. This rapid expansion also creates a significant cooling effect (the horn becomes extremely cold — never hold the horn directly).
The CO2 gas displaces oxygen around the fire, breaking the combustion triangle. Because it leaves no residue — unlike powder or foam extinguishers — it is ideal for protecting electronic equipment, server rooms, commercial kitchens (for electrical fires only), and any environment where contamination would cause secondary damage.
CO2 extinguishers are not suitable for Class A fires (ordinary combustibles like wood and paper — CO2 does not cool the material sufficiently to prevent re-ignition), Class F fires (cooking oils — risk of hot oil splatter), or use in confined spaces (risk of oxygen depletion for the user).
CO2 extinguishers are the standard choice for:
Under BS 5306-8, CO2 extinguishers should generally be provided alongside a water or foam extinguisher in offices and commercial premises, since CO2 alone is not effective on Class A materials which make up the majority of office combustibles.
Under BS EN 3 and the UK's colour coding scheme (BS 7863:1996), CO2 extinguishers are identified by a black label panel on a red body. This replaced the older all-black body that was used before 1997. Never use a fire extinguisher unless you have confirmed it is the correct type for the fire — check the label and colour coding.
Under BS 5306-3:2017, CO2 extinguishers require:
Servicing must be carried out by a competent person as defined in BS 5306-3. The BFC EAL Level 3 Fire Extinguisher qualification is the recognised standard for competence in extinguisher maintenance across all extinguisher types, including CO2.
A CO2 (carbon dioxide) fire extinguisher is a portable firefighting device that discharges pressurised carbon dioxide gas to smother a fire by displacing oxygen. It leaves no residue, making it the preferred choice for electrical equipment, server rooms, and environments where contamination cannot be tolerated.
Requirements for co2 fire extinguisher in the UK depend on the type of premises and applicable legislation, including the Regulatory Reform (Fire Safety) Order 2005 and relevant British Standards. The responsible person for a premises must ensure adequate fire safety provisions are in place. The British Fire Consortium can provide guidance — contact our team or search our member directory to find a qualified specialist.
CO2 Fire Extinguisher and Fire Classes are related fire safety concepts but serve different purposes. See our individual glossary entries for detailed definitions. For expert guidance on which applies to your premises, consult a BFC member company.
The British Fire Consortium offers EAL Level 3 accredited training covering fire safety systems including topics related to co2 fire extinguisher. Our courses are the only nationally recognised Level 3 qualifications across all fire disciplines. View our training courses or use the member directory to find a qualified trainer near you.
