Carbon monoxide
Carbon monoxide safety: signs, alarms and the law
Carbon monoxide is the hidden risk of gas appliances. It has no colour or smell, and its early symptoms are easily mistaken for everyday illnesses. Here's what HSE says to look for, and the alarm rules that now apply to rented homes in England.
Short answer
Carbon monoxide comes from fuel-burning appliances that are faulty, badly installed, poorly ventilated or have blocked flues. HSE says around seven people a year die from gas-related CO poisoning. Get appliances serviced by a Gas Safe registered engineer, fit an alarm, and seek urgent medical advice if you suspect exposure.
The risk
Why carbon monoxide is so dangerous
When gas burns properly, it produces mainly carbon dioxide and water. When it burns badly, because an appliance is faulty, the flue is blocked or there isn't enough ventilation, it can produce carbon monoxide. You can't see, smell or taste it.
HSE's figures put the cost plainly: every year around seven people die from carbon monoxide poisoning caused by gas appliances and flues that haven't been properly installed, maintained or are poorly ventilated. That's why HSE advises having gas appliances, flues and pipework serviced at least annually by a Gas Safe registered engineer.
The symptoms
What to look out for
HSE lists these symptoms of carbon monoxide poisoning:
- headaches or dizziness
- breathlessness
- nausea
- loss of consciousness
- tiredness
- pains in the chest or stomach
- erratic behaviour
- visual problems
HSE warns that early symptoms can mimic many common ailments and be confused with food poisoning, viral infections, flu or simple tiredness. Symptoms that ease when you leave the house, or that several people or pets share, are reasons to suspect it.
Rented homes in England
The alarm rules since 1 October 2022
| Requirement | Applies to |
|---|---|
| Carbon monoxide alarm in any room used as living accommodation with a fixed combustion appliance, excluding gas cookers | Private and social landlords |
| At least one smoke alarm on every storey used as living accommodation | Private and social landlords |
| A decorative, non-working fireplace | Not a fixed combustion appliance, in the department's view |
If an alarm sounds
What to do
- Stop using gas and other fuel-burning appliances.
- Open doors and windows and get everyone, including pets, into fresh air.
- If anyone has symptoms, seek urgent medical advice from a GP or A&E, and tell them you suspect carbon monoxide.
- If you also smell gas, call 0800 111 999.
- Don't use the appliances again until a Gas Safe registered engineer has checked them.
Tenants should tell their landlord straight away; landlords must keep gas appliances they provide safe.
Prevention
Keeping the risk down
- Have gas appliances serviced at least annually by a Gas Safe registered engineer qualified for each one, as HSE advises.
- Keep vents and air bricks clear; don't block them to stop draughts.
- Keep flues and chimneys clear; HSE says chimneys should be regularly swept where appliances use them.
- Fit an audible carbon monoxide alarm in rooms with fuel-burning appliances, and test it regularly.
- Watch for soot or staining around appliances.
Liverpool
Why it matters in a gas-heated, rented city
Census 2021 shows 77.8% of Liverpool households heating with mains gas alone, and more than half renting their home. That puts a lot of gas appliances in homes where the appliance belongs to someone other than the person living there. The annual gas safety check and the 2022 alarm rules exist for exactly that situation. If you rent and don't have a working CO alarm in a room with a boiler or gas fire, ask your landlord about it.
Worth it
A small cost against a serious risk
An alarm and an annual service are modest, predictable costs. Set against a risk HSE measures in deaths each year, they're among the most sensible spending in a gas-heated home. If you're a landlord, they're also part of meeting your legal duties. See boiler servicing and landlord gas safety.
Other fuels
Not just gas
Carbon monoxide can come from any fuel-burning appliance, including oil boilers, wood-burners, coal fires and some portable heaters. HSE advises that appliances burning other fuels are serviced and maintained by a competent person and their chimneys regularly swept. In rented homes, the 2022 alarm rules apply to any fixed combustion appliance, not only gas. If you use more than one kind of appliance, think about each one when deciding where alarms should go, and follow the alarm manufacturer's instructions on placement.
Portable gas heaters and appliances used in caravans, boats or outbuildings need the same care: good ventilation, regular checks by a competent person, and an alarm where people sleep or spend long periods.
Carbon monoxide questions
What are the symptoms of carbon monoxide poisoning?
HSE lists headaches or dizziness, breathlessness, nausea, loss of consciousness, tiredness, chest or stomach pains, erratic behaviour and visual problems. They can be mistaken for flu or food poisoning.
Do landlords have to fit carbon monoxide alarms?
Yes, in England since 1 October 2022: in any room used as living accommodation with a fixed combustion appliance, excluding gas cookers. This applies to private and social landlords.
Where should a CO alarm go?
In the room with the appliance. Follow the alarm manufacturer’s instructions on height and distance from the appliance.
What causes carbon monoxide in a home?
Appliances that burn fuel and aren’t properly installed, maintained or ventilated, or whose flues are blocked. HSE says around seven people a year die from gas-related CO poisoning.
Testing
Look after the alarm
Test a carbon monoxide alarm regularly using its test button, replace it when the manufacturer says, and never take the batteries out. If you rent, tell your landlord straight away if an alarm stops working.
Sources used on this page
- Carbon monoxide poisoning · HSE (3 November 2026)
- Domestic gas: frequently asked questions · HSE (3 November 2026)
- Smoke and carbon monoxide alarm regulations: Q&A for the private rented sector · GOV.UK (3 November 2026)
- Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022: guidance · GOV.UK (3 November 2026)
- Landlords’ responsibility for gas safety · HSE (3 November 2026)
- Census 2021 TS046, central heating, Liverpool and England · Nomis (3 November 2026)
- Census 2021 TS054, tenure, Liverpool and England · Nomis (3 November 2026)
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