Carbon monoxide poisoning is caused by breathing a gas that has no smell, colour or taste, which makes it especially dangerous. It is produced when fuel burns without enough air, from gas heaters, water heaters, blocked flues, generators, charcoal burned indoors and vehicle exhaust in garages. Carbon monoxide binds to red blood cells about 200 to 300 times more readily than oxygen, so the blood carries less oxygen to the brain and heart. Quick recognition and safe rescue save lives.
Symptoms of Carbon Monoxide Poisoning
- Headache, often the first sign, and dizziness or giddiness
- Nausea and vomiting
- Yawning, weakness and tiredness
- Blurred or diminished vision
- Rapid pulse, chest pain or breathlessness
- Confusion, drowsiness, fainting and unconsciousness
- Seizures in severe exposure
Cherry-red skin is often described but is rare and appears late, so do not wait for it. Several people in the same room developing headaches and nausea should raise suspicion of carbon monoxide poisoning.
Rescue Safety: Do Not Become the Next Victim
- Do not enter a gas-filled space, confined space, tank, drain or tunnel unless you are trained and have approved breathing apparatus and lifelines.
- Check hazard signs and call the fire service. In a workplace, alert the safety officer or the person responsible for the area.
- Ventilate by opening doors and windows from outside if safe, and turn off the fuel source where you can do so safely.
- Prohibit smoking, naked flames and switches that could cause sparks.
Carbon Monoxide Poisoning First Aid Steps
- Move the person to fresh air as soon as it is safe to do so.
- Call the emergency number. Every person with suspected carbon monoxide poisoning needs medical assessment.
- Check DRABC following the primary survey, and start CPR if breathing stops.
- Give oxygen if you are trained, using a high-flow mask. In the workplace, notify the occupational health nurse, doctor or accredited first aider who can give oxygen.
- Loosen tight clothing, keep the person warm and rest them, even if they feel better.
- Place an unconscious breathing person in the recovery position and monitor them.
- Flush contaminated skin or eyes if the exposure included other chemicals.
Why Hospital Assessment Matters
Symptoms can worsen after the person leaves the gas, and some people develop delayed brain effects days or weeks later. Doctors may measure carboxyhaemoglobin, give 100 per cent oxygen and consider hyperbaric oxygen therapy in severe cases. Pregnant women, children, older adults and people with heart or lung disease are at higher risk.
Preventing Carbon Monoxide Poisoning
Install carbon monoxide alarms, service gas appliances and flues, never run generators or vehicles in enclosed spaces, never burn charcoal indoors or in closed rooms and make sure heating is ventilated. Workplaces should include carbon monoxide in confined space procedures and train staff in carbon monoxide poisoning first aid. See also inhalation burns first aid for smoke exposure.
Frequently Asked Questions
Can I smell carbon monoxide?
No. It is odourless and colourless, so alarms and good ventilation are essential.
Do I need hospital care if I feel better in fresh air?
Yes. Symptoms can return and delayed effects can occur, so a medical check is advised.
References and Further Reading
- NHS, Carbon monoxide poisoning
- American Heart Association and American Red Cross, Guidelines for First Aid
Last updated: November 2026
Prepared by: EHS Guidelines Editorial Team
This article is general educational information and is not a substitute for accredited first aid training or professional medical care. In an emergency, call your local emergency number immediately. Emergency numbers, medicines and protocols differ between countries, so follow local guidance.
Related Guides
- Poisoning First Aid: What to Do When Someone Swallows a Poison
- Inhalation Burns: Mouth, Throat and Airway Burns After Smoke or Hot Gases
- Vital Signs Observations: Pulse, Breathing, Conscious State and Skin
- Recovery Position: A Step by Step Guide
- CPR for Adults: Current Technique and Compression Ratios
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