An estimated 12 million UK homes are not protected by a carbon monoxide alarm, it has been predicted.
Nearly half (46%) of the 2,000 people questioned said they do not have the device, potentially putting themselves at risk of CO poisoning.
Families are more likely to fit a smoke alarm (83%), double glazing (76%) or window locks (70%) than have a CO alarm (54%), according to research commissioned by the Gas Safe Register.
Jonathan Samuel, Gas Safe Register chief executive, said: "We are encouraging families to ask a Gas Safe registered engineer to check that their gas appliances are safe and sound as a first line of defence from potential CO poisoning.
"Worryingly, nearly half of the people we asked didn't know the signs of dangerous gas appliances - a key cause of CO poisoning.
"The signs that your gas appliance isn't working safely are: a lazy yellow flame instead of a crisp blue flame, soot or staining on or around the appliance, or excess condensation in the room."
For more information, visit www.StayGasSafe.co.uk