Public liability insurance holders have been told that only people on the Gas Safe Register are permitted to work with gas appliances.
In the Health and Safety Executive's (HSE's) myth of the month for January, it advises that "gas and cowboys do not mix", adding that anyone working with these type of appliances has to be registered by law.
"The person you're using isn't registered then they might not be safe and they are also breaking the law. Incorrectly fitted or badly repaired gas appliances can lead to carbon monoxide poisoning, gas leaks, fires and explosions," the guide added.
Public liability insurance holders were told that gas fitters should carry a Gas Safe ID card, which will show people that they are qualified to do the work.
In November, the HSE prosecuted former Bury St Edmunds resident Jim Price after he pleaded guilty to working on a gas boiler while not registered.
Mr Price was fined £250 with £250 in costs and ordered to pay £1,150.74 in compensation to the affected householder.