Safety checks must be carried out on gas appliances to make sure they are fit for purpose, public liability insurance holders have been told.
The warning comes after landlord Graham Barnes, 49, from Kidlington, was prosecuted by the Health and Safety Executive (HSE) for failing to have gas fittings checked at a property he rented out.
Didcot Magistrates Court heard that between January and July 2009, Mr Barnes failed to arrange annual safety checks. He was fined a total of £8,000 and ordered to pay £1,957.70 in costs.
Dozie Azubike, HSE inspector, told public liability insurance holders that this was a clear case of a landlord ignoring his responsibilities and putting people at risk.
"As a result of the boiler not being serviced, carbon monoxide leaked into the kitchen creating a very dangerous environment," he added.
Last year, public liability insurance holders were given gas appliance warnings when landlord Helen Beckett of Ilkley was fined £1,000 after she pleaded guilty to breaching Regulation 36(3) of the Gas Safety (Installations and Use) Regulations 1998.