Carbon Monoxide (CO)

Published June 2026, replacing April 2022

Carbon monoxide is a poisonous gas produced when fuels burn without enough oxygen.

It is a serious danger to health and can cause death.

Carbon monoxide is slightly lighter than air and mixes freely with air. It is difficult to recognise as it has no colour, smell or taste. This means you can breathe it in without knowing.

Make sure people understand the dangers of carbon monoxide and know the symptoms to look out for. This is an important safety measure.

What to do in an emergency?

Supporting resources

Hazards

The primary source of exposure to carbon monoxide is from cooking or other fuel burning appliances which are badly installed, faulty or used incorrectly (including inadequate ventilation). 

Fuels will be:

• Gas (LPG)
• Wood
• Oil
• Coal

A common fuel-burning appliance could be:

• Portable stoves
• Barbecues
• Gas fires
• Water heaters
• Solid fuel stoves/ wood burners
• Engines

You can include the following in your risk assessments, along with your plans for how to respond to incidents, making sure that everyone knows what actions to take in an emergency.

Safety controls

Adequate ventilation

• Make sure there is adequate ventilation and clearance in enclosed spaces. If you need an outdoor sheltered cooking area, use a gazebo or a tent porch with good air circulation and ventilation. When using appliances in mess tents, party tents or marquees, keep the doors and ventilation mesh open at all times.
• Have chimneys and flues cleaned at least once a year by a qualified sweep. Do not block them up.

Correct use and checking of equipment

• Follow the manufacturer’s instructions carefully. Check the appliance has the correct gas type and enough supply.
• Have all fossil fuel burning appliances serviced regularly by a qualified and registered engineer, such as Gas Safe Register (for gas appliances), HETAS (for solid fuel appliances) and OFTEC (for oil appliances).
• Regular visual inspections can be carried out by a competent person. They should check the equipment before each use to make sure it is in good condition. Make sure that any recommended remedial actions are carried out promptly.
• If soot forms when burning, shut off the appliance and it serviced by a Gas Safe Engineer before using it again.

Correct detection for Carbon Monoxide

• Make sure you have an audible carbon monoxide (CO) alarm that meets British Standards. This helps protect you from exposure to dangerous levels of carbon monoxide. It’s important to have the right type of alarm for where you are using it:
  
  • BS EN 50291‑1 alarms are designed for indoor residential buildings, such as meeting places, and buildings that have permanent accommodation.
  • BS EN 50291 2 alarms are portable and designed for use in temporary or mobile settings, such as caravans, campervans and camping.
• Alarms should be positioned, maintained and tested in accordance with the manufacturer’s instructions and the advice given within Think CO: Carbon Monoxide Awareness for Scouts, on My Learning.
• Alarms have a 10-year service life, and you should record the date it goes into service on the device so that it is clearly visible.
• Brief people about what to do if they hear the CO alarm go off. Always treat it as a real emergency.

Understand the symptoms

A brief exposure to small amounts of carbon monoxide may cause:

• Headache
• Flushing
• Nausea, dizziness or vertigo
• Muscle pain
• Memory problems or changes in behaviour

Exposure to higher amounts may cause:

• Problems with movement
• Weakness
• Confusion
• Lung and heart problems
• Loss of consciousness
• Death

It can be difficult to tell the difference between the effects of long-term, low-level exposure to carbon monoxide, and other common illnesses.

• Children, pregnant women, older people, and people with diseases such as coronary heart disease, angina, asthma or anaemia are particularly at risk of harm
• Altitude, physical activity, and current or previous exposure to carbon monoxide may also affect how sensitive a person is to the negative effects of carbon monoxide.

Having an emergency plan if there is an incident

If your carbon monoxide (CO) alarm sounds, or you suspect exposure to carbon monoxide (note: unignited gas does not contain carbon monoxide), act immediately — do not wait:

• Move everyone into fresh air straight away by evacuating the area or premises. Stay calm and act quickly.
• Extinguish all naked flames and turn off any fuel-burning appliances, if it is safe to do so.
• Close cylinder valves where possible.
• Open windows and doors as you leave, if safe, to help ventilate the area.
• Call the emergency services and seek medical advice.

Do not re‑enter the area or premises until emergency services confirm it is safe. Do not use any equipment again until it has been checked for faults or leaks and fully repaired.

Be aware that appliances can continue to produce carbon monoxide for some time, even after they have been turned off or extinguished.

Learn to recognise the sound of your CO alarm, as it is different from a fire alarm.

Symptoms of carbon monoxide exposure may improve once people are away from the source, but it is still important to seek medical advice.

Frequently asked questions