Carbon dioxide (CO2) extinguishers are the go-to choice for fires in electrical equipment. They put out the fire by removing the oxygen around it, and leave no mess behind.

When You Need One

Our standard advice for most fire points is a 6 Litre Water Fire Extinguisher, plus a 2kg CO2 Fire Extinguisher where there's electrical equipment. If there's no electrical risk nearby, you don't need the CO2.

The British Standard for extinguisher provision (BS 5306-8:2023) recommends dedicated extinguishers next to the electrical mains intake and distribution boards, as these are a common cause of fires. That's where a CO2 is most clearly needed.

Many water-based extinguishers – water, water additive, water mist and foam – have passed the electrical (dielectric) test, so they're safe if they're accidentally used on electrical equipment. Check the label to see if yours has. If it has, you usually won't need a separate CO2 – except next to distribution boards and similar electrical hazards, where a CO2 is still the right choice. See Service-Free (P50) Extinguishers Explained and Water Mist Fire Extinguishers Explained.

Which Size?

  • 2kg – offices, shops, and anywhere with computers and everyday electrical equipment. It weighs about 5 kg in total. Typical rating: 34B.
  • 5kg – larger electrical risks such as plant rooms, server rooms, workshops and main switchgear. It weighs about 14 kg in total. Typical rating: 70B.
  • Larger wheeled units – for high-risk industrial sites.

Ratings vary between models, so check the label. See Fire Classes Explained for what the numbers mean.

What CO2 Is Good For – and Not

  • Electrical equipment – CO2 doesn't conduct electricity.
  • Flammable liquids (Class B) – such as petrol, oil and solvents. Less effective outdoors, where the wind can blow the gas away.
  • No residue – ideal where there's sensitive equipment.
  • Not for paper, wood or fabric (Class A) – the gas disperses quickly and the fire can reignite. That's why we pair it with a water extinguisher.
  • Not for cooking oil fires – use a wet chemical extinguisher. See Commercial Kitchen Fire Safety.

How Far Away Should It Be?

BS 5306-8:2023 recommends that nobody should have to travel more than 30 m to reach an extinguisher for general electrical cover, or 10 m for a dedicated extinguisher protecting a specific hazard. Take off 5 m for each door that has to be opened on the way. See How Many Fire Extinguishers Do I Need?.

Using a CO2 Safely

  • Hold it by the handle, not the horn. The gas comes out at about −78°C and can cause cold burns – choose a model with a frost-free horn.
  • CO2 removes oxygen from the air. Don't use one in a small, enclosed space where people could be overcome. Once the fire's out, leave and let the area ventilate.
  • They're very loud when in use, which can take you by surprise if you're not expecting it.

See How to Use a Fire Extinguisher.

Servicing

Like all extinguishers, CO2s need a basic service every year. Instead of the 5-yearly extended service other types have, they need an overhaul at 10 years. See Do Fire Extinguishers Need Servicing?.

Worth remembering… your fire risk assessment is what decides what your premises need. This guide is general advice, not a substitute for it.

Not sure what you need? Get in touch with our team – we'll be delighted to help. No pressure. No sales patter.