Quick answers
When is it dangerous to use a carbon dioxide fire extinguisher?
In a small, closed or badly ventilated room, because the gas pushes oxygen out of the air and people can suffocate. It is also risky on an electrical fire if the power has not been switched off.
Can a CO₂ extinguisher cause frost burns?
Yes. The gas gets extremely cold as it comes out, so touching the horn or the discharge pipe, or using an older unit without a frost-free horn, can burn the skin. Hold it only by the handle.
Which fires is a carbon dioxide extinguisher meant for?
Flammable liquid (Class B) fires and fires in electrical equipment. That makes it a good fit for garages, workshops, factories, electrical panel rooms and server rooms.
Can I use a CO₂ extinguisher on burning wood or paper?
It is not the right choice. CO₂ does little cooling, so wood, paper and cloth can flare up again once the gas drifts away. Keep a suitable extinguisher for ordinary combustibles as well.
Why does a CO₂ extinguisher need careful handling?
It is stored at high pressure, it can jerk as it discharges and it empties very quickly. Staff should be trained on which fires it suits and how to hold and aim it before they ever need it.
Most offices, workshops and server rooms in India keep a carbon dioxide (CO₂) extinguisher near the electrical panel. It is the black-and-red cylinder with a wide horn instead of a hose nozzle. It is very good at its job, but it can also hurt the person using it, or the people standing in the room. This page explains when it is risky to use one, and how to use it safely.
How a CO₂ extinguisher puts out a fire
CO₂ is a gas with no colour and no smell. When you squeeze the handle, it rushes out of the horn and pushes the oxygen away from the fire, and the flames die down. Because it leaves no powder or water behind, it suits flammable liquid fires (Class B) and fires in electrical equipment.
The same thing that puts out the fire is what makes it dangerous to you. In a small room, the gas does not stop at the flames. It pushes the oxygen out of the air you are breathing too.
When it is dangerous to use a CO₂ extinguisher
- In a small, closed room. In a store room, a cabin with the door shut, a basement or any space with poor ventilation, discharging CO₂ can leave too little oxygen to breathe. People can get dizzy, collapse and suffocate. Use it from the doorway if you can, and get out as soon as it is empty.
- When you grab the horn. The gas gets extremely cold as it comes out. Holding the horn or the discharge pipe with bare hands, or using an older unit without a frost-free horn, can give you a frost burn. Hold the unit only by its handle.
- When you are not ready for the force. The gas is stored at high pressure and the discharge can jerk the horn in your hands. Grip the unit firmly and brace yourself before you squeeze.
- When you expect it to last. A CO₂ unit empties very quickly. If you waste the first few seconds aiming badly, it may run out before the fire is out.
- On a live electrical fire with the power still on. CO₂ does not conduct electricity, but the fault that started the fire is still there. Switch off the power at the main switch or MCB first, if you can do it safely, or the fire can start again and someone can get a shock.
Where a CO₂ extinguisher makes sense
Put CO₂ units where the risk is flammable liquids or electrical equipment: auto garages, two-wheeler service centres, workshops, manufacturing plants, electrical panel rooms, server rooms and IT facilities.
It is not the right choice for burning wood, paper, cloth or cartons. CO₂ does very little cooling, so these materials can flare up again once the gas drifts away. Keep a suitable extinguisher for ordinary combustibles nearby as well, and take advice from a competent fire-safety supplier on which types your premises need.
Training and safe use at work
- Train the people who will use it. Nobody should be using one for the first time on the day of a fire.
- Cut the power first. Offices and factories in India run a lot of electrical equipment on crowded boards. Teach staff where the main switch is, and to isolate the supply before they fight an electrical fire, if they can reach it safely.
- Think about air. In a small panel room or store, a CO₂ discharge can make the air unsafe. Put a sign near the unit telling people to leave and ventilate the room after use. Rooms protected by fixed CO₂ systems need warning signs, and everyone should know to get out when that alarm sounds.
- Keep units serviced. Get CO₂ extinguishers weighed and serviced by a competent agency as the label requires. A unit that has lost gas will not do its job.
If you have to use one
Raise the alarm first. Switch off the power if you can reach the switch safely. Keep the exit behind you, pull the pin, aim the horn at the base of the fire and sweep. Once it is empty, step back and watch for a flare-up, and leave a small room straight away. If you feel dizzy, get to fresh air. If the fire is not out quickly, leave, close the door and call 101 for the fire brigade or 112.
Tomorrow at work, find the CO₂ extinguisher nearest your desk and read its label. Check how big the room it protects is, and ask who on your floor has been trained to use it.
What needs attention
- CO2 puts out a fire by pushing away oxygen, which is also what makes it dangerous to people in a small room
- In a closed space with poor ventilation, discharging CO2 can leave too little oxygen to breathe
- The horn gets extremely cold during discharge and can cause frost burns
- CO2 units empty fast and do not cool the fire much, so it can flare up again
- CO2 suits flammable liquids and electrical equipment, but switch off the power first if you safely can
Controls that reduce risk
- Place CO2 units where they suit the risk: electrical panels, server rooms, workshops with flammable liquids
- Put a sign near CO2 units in small rooms warning people to leave after use
- Train staff on how to hold the unit by the handle and how fast it empties
- Have an extinguisher suited to ordinary combustibles nearby as well
- Get CO2 units weighed and serviced by a competent agency as the label requires
- Check that rooms protected by fixed CO2 systems have warning signs and that people know to leave when the alarm sounds
Common unsafe practices
- Using a CO2 extinguisher in a small, closed room and staying inside
- Holding the metal horn or the discharge pipe with bare hands
- Using CO2 on burning wood, paper or cloth, which can reignite
- Walking away as soon as the flames go out
- Fighting an electrical fire without trying to isolate the power
- Using an extinguisher you have never been trained on
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