- Energised electrical equipment where a portable extinguisher is justified
- Class B flammable-liquid fires within the marked rating
- Server, communications and office equipment areas
- Clean-discharge applications where residue would cause serious damage
Electrical equipment and Class B risks
CO₂ fire extinguishers: uses, colour and safety guidance
CO₂ leaves no residue and is widely used around electrical equipment. Understand its limited cooling, re-ignition risk and important discharge precautions.
Page summary
CO₂ extinguishers at a glance
The fire risk assessment should determine whether this extinguisher is appropriate, the fire rating required and where it should be positioned. Colour helps identification; it does not replace reading the label.
- Non-conductive and leaves no residue
- Common near electrical equipment
- Normally carries a Class B rating
- Limited cooling can allow re-ignition
Correct selection
What co₂ extinguishers can—and cannot—be used for
No single portable extinguisher is suitable for every fire. Use only equipment selected for the premises and only on the classes and conditions stated on its label.
- Deep-seated Class A fires as the sole agent
- Cooking oils and deep-fat fryers
- Flammable gas leaks unless specifically planned and isolated
- Combustible metals
- Unventilated or confined spaces where gas accumulation may endanger people
How it controls fire
How a co₂ extinguisher works
Carbon dioxide reduces the local oxygen concentration around the flame and has some cooling effect as it expands. It evaporates without leaving powder, foam or water residue.
Because CO₂ provides limited cooling, hot Class A material or an unisolated energy source can re-ignite after the gas disperses. The discharge horn becomes extremely cold, and unsafe handling can cause cold burns.
Premises examples
Where this extinguisher may be considered
These are prompts for assessment, not ready-made specifications. Building use, quantities, people at risk and other protection can change the answer.
Offices
Frequently paired with suitable Class A provision near computers, printers and electrical equipment, with staff trained to identify the correct unit.
Server and communications rooms
Clean discharge can protect sensitive equipment, but room design, automatic systems, ventilation and life safety may require specialist coordination.
Laboratories and workshops
May cover suitable electrical or limited Class B hazards where chemical compatibility and room conditions have been assessed.
Retail and hospitality back-of-house areas
Can address electrical appliances, but commercial cooking-oil risks require separate Class F provision.
Before specifying equipment
Selection points that matter
Do not buy by colour or cylinder size alone. A competent selection considers the hazards, certified ratings, likely users, positioning and interaction with the emergency plan.
Re-ignition
Remove or isolate the energy source where safe. CO₂ may knock down flames without cooling the fuel enough to prevent recurrence.
Room volume
Discharge can reduce breathable oxygen. Confined and poorly ventilated spaces need particular care, warning and specialist assessment.
Horn safety
Follow the product instructions and hold only the designed insulated grip. The horn and discharge components can become cold enough to injure skin.
Rating and size
A larger cylinder is not automatically the right answer. Consider fire rating, carrying weight, discharge duration, access and likely users.
Life safety comes first
Portable extinguishers support escape; they do not make firefighting compulsory
Raise the alarm, begin the evacuation procedure and call 999. A person should only consider using an extinguisher if they have been instructed or trained, the fire is small, the correct unit is available, smoke is not affecting them and a clear escape route remains behind them. Never delay evacuation or take personal risk.
Inspection and servicing
Keep the provision usable and correctly specified
Routine checks should identify discharged, damaged, missing, obstructed or out-of-date equipment. Competent servicing should confirm condition, agent, rating, position, signage and records, while the fire risk assessment should be reviewed when hazards or layouts change.
BAFE’s SP101 scheme provides third-party certification for organisations that commission and maintain portable fire extinguishers. Certification can be useful evidence, but check that the provider’s current scope covers the work required.
Frequently asked questions
CO₂ extinguisher FAQs
What colour is a CO₂ extinguisher?
Modern UK CO₂ extinguishers normally have a red body with a black identification band. They also commonly have a distinctive discharge horn, but the label and ratings are the reliable identifiers.
What is a CO₂ fire extinguisher used for?
It is commonly selected for electrical equipment and carries a Class B rating for suitable flammable liquids. It leaves no residue, which can be valuable around sensitive equipment.
Can CO₂ be used on paper or wood?
It may temporarily suppress flames, but its limited cooling makes re-ignition of deep-seated Class A material likely. A suitably rated water-based extinguisher is normally used for that hazard.
Why should you not touch the CO₂ horn?
The discharge rapidly cools the horn and other components. Touching an uninsulated part can cause a cold burn, so users must follow the extinguisher’s handling instructions.
Is CO₂ safe in a small room?
Carbon dioxide can displace oxygen, particularly in confined or poorly ventilated spaces. People must not be placed at risk to fight a fire; evacuation and the premises emergency procedure come first.
Sources and limitations
Guidance checked against authoritative UK sources
This is general information, not an extinguisher specification or instruction to fight a fire. The selection, number, rating and position of extinguishers depend on a suitable and sufficient fire risk assessment, recognised guidance, manufacturer instructions and the actual premises.