Eight million homes do not have potentially life-saving carbon monoxide alarms, research shows.
To help protect households, the Daily Mirror has teamed up with British Gas to give away 1,000 of the alarms to readers for free.
Of those who do not have one of the devices, one in five said it is because they keep forgetting.
One in six were unaware they need one, the British Gas survey found.
Have you got a carbon monoxide alarm? Join the discussion in the comment section
Rob Topping, a safety assurance engineer with the company, said: “Carbon monoxide poisoning is a silent killer that can easily be prevented with some simple measures.”
The steps include annual safety checks and ensuring you have a working alarm.
Carbon monoxide, a poisonous gas with no smell, is produced when fuels such as gas and oil do not burn fully.
Each year there are about 60 deaths from accidental carbon monoxide poisoning in England and Wales.
Symptoms can include a tension-like headache, dizziness and feeling sick.
The alarms that detect the gas often cost less than £30.
Gas Safety Week runs until Sunday.
To get a free carbon monoxide alarm and for full terms and conditions, visit www.mirror.co.uk/freealarm. The offer closes on Tuesday or when availability ends.
