For fires involving live electrical equipment, use a CO2 (carbon dioxide) extinguisher. It does not conduct electricity, leaves no residue and can reach inside equipment casings. Dry powder also works on electrical fires, but it is not recommended inside buildings and can damage equipment. Water mist, and some water or foam extinguishers, may be used only if the label says they have passed the 35 kV dielectric test, and then only up to the stated voltage, typically 1000 V at a distance of 1 m. Never use a standard water or foam extinguisher on live electrics.
This guide explains which types of fire extinguisher you should use on live electrical equipment, the limits of each type, and how to choose extinguishers for offices, plant rooms and workshops.
First: isolate the power if it is safe to do so
UK fire and rescue services advise that if there is an electrical fire, you should pull the plug out or switch off the power at the fuse box or distribution board, but only if it is safe to do so. Sometimes this alone stops the fire. Never put water on an electrical fire. If the fire is growing, or you are not trained and confident, get out, stay out and call 999.
Electrical fire extinguishers at a glance
| Extinguisher | Use on live electrical equipment? | Points to note |
|---|---|---|
| CO2 (black label) | Yes: the primary choice | No residue. Not rated for Class A solids. Take care in small, enclosed rooms. |
| Dry powder (blue label) | Yes, with caveats | Not recommended inside buildings. The residue can seriously damage equipment. |
| Water mist | Only where the label says so | Look for 35 kV dielectric test approval and the stated voltage and distance (typically 1000 V at 1 m). |
| Foam (cream label) | Only if dielectrically tested, and only to the stated voltage | Treat an untested foam extinguisher as unsafe on live equipment. |
| Water (red) | No, unless the label confirms dielectric testing | Never use a standard water extinguisher on live electrics. |
| Wet chemical (yellow label) | No, unless the label says otherwise | Designed for Class F cooking oil fires. |
CO2 extinguishers: the first choice for electrical fires
Carbon dioxide extinguishers are rated for Class B flammable liquids and for electrical equipment. Government fire safety guidance for small premises recommends a CO2 extinguisher to deal with fires involving electrical equipment. Some fire services suggest at least one 2 kg CO2 extinguisher, or another extinguisher rated for electrical fires, wherever there is electrical equipment.
CO2 is a gas, so it can flood an enclosure and reach the seat of a fire inside equipment. It leaves no residue on computers, switchgear or machinery. That makes it well suited to offices and other areas with a lot of electrical equipment.
Keep these limitations in mind:
- It is not rated for Class A fires. Once the power is off, a fire that has spread to paper, furniture or packaging may need a water-based or foam extinguisher.
- It can affect people in confined spaces. Take care using CO2 in small or poorly ventilated rooms, and follow the instructions on the extinguisher label.
Browse CO2 fire extinguishers.
Dry powder extinguishers: effective, with caveats
ABC dry powder is an accepted agent for electrical fires and also covers Class A, B and C fires. It has two drawbacks indoors:
- Visibility and breathing. Some fire and rescue services do not recommend powder extinguishers inside buildings, because the cloud of very fine dust can disorientate the user and cause discomfort.
- Equipment damage. The powder gets into electronics and can cause significant secondary damage.
Follow your fire risk assessment on where powder is appropriate. Browse powder fire extinguishers.
Water mist extinguishers: only where rated
Water mist extinguishers discharge very fine droplets, typically of de-ionised water, through a special nozzle. Models that pass the 35 kV dielectric test in BS EN 3-7 are marked as suitable for use on live electrical equipment, typically up to 1000 V at a distance of 1 m. Many are also rated for Class A and Class F fires, so one extinguisher can cover several mixed risks.
Always check the label. If a water mist extinguisher does not state an electrical rating, do not use it on live equipment, and never use it above the stated voltage or closer than the stated distance. Browse water mist fire extinguishers.
Foam and water: never unless dielectrically tested
BS EN 3-7 includes a dielectric test for water-based extinguishers. A metal plate is charged to 35,000 V at 1 m from the nozzle, and the current through the extinguisher is measured during discharge. Passing the test means the extinguisher is safer if it is used close to, or accidentally sprayed onto, electrical equipment.
However, many foam and water extinguishers do not clearly state that they are suitable for deliberate use on live equipment. The safe rule is simple:
- Never use a standard water or foam extinguisher on live electrical equipment.
- Use a water-based extinguisher on electrical equipment only if its label specifically says it is suitable, and only up to the voltage and from the distance stated.
- Even when tested, water-based agents struggle to reach a fire inside an enclosure, which is why CO2 remains the best choice in many situations.
Other options for electrical and battery risks
Clean agent extinguishers
Some clean agent extinguishers, such as fluoroketone units, are described by their manufacturers as leaving no residue and having high dielectric strength. Check the ratings on the label before you rely on one for electrical risks.
Lithium-ion battery fires
Lithium-ion batteries, such as those in e-bikes, scooters and battery storage, are a specialist fire risk, and specialist extinguishers are available for them. See our lithium-ion battery fire safety guide. Check the manufacturer's stated ratings against your fire risk assessment. Browse lithium battery fire extinguishers.
Choosing extinguishers for premises with electrical equipment
- Base the type, number and position of extinguishers on your fire risk assessment.
- Government guidance for small premises recommends a water-based extinguisher for combustible materials, plus a CO2 extinguisher for fires involving electrical equipment.
- Kitchens with fat fryers should also have a Class F (wet chemical) extinguisher and a fire blanket.
- Have extinguishers serviced annually by a competent person under BS 5306-3.
Compare the full range of fire extinguishers, or read our guide to fire extinguisher colours and types. We supply genuine, brand-new, factory-sealed products with fast, tracked UK delivery.
Frequently asked questions
What fire extinguisher should you use on an electrical fire?
A CO2 extinguisher is the primary choice. Dry powder also works but is not recommended indoors. Water mist or foam should only be used if the label confirms a dielectric test, and then only up to the stated voltage and distance.
Can you use a powder extinguisher on electrical fires?
Yes. ABC powder is suitable for electrical fires, but the powder cloud reduces visibility indoors and the residue can seriously damage electrical equipment.
Can you use a foam extinguisher on an electrical fire?
Only if the label says it has passed the 35 kV dielectric test and is suitable for live equipment, and only up to the stated voltage, typically 1000 V at 1 m. Otherwise, no.
Is there a Class E fire in the UK?
No. UK fire classes are A, B, C, D and F. Electrical fires are treated as a risk rather than a class, and extinguishers that are suitable say so on their label. See our guide to the classes of fire.
What colour is a CO2 extinguisher?
A CO2 extinguisher has a red body with a black band or label panel.
This guide is general information; follow your fire risk assessment and a competent person's advice.