David Ian Douglas-Law of Penally, Tenby, was fined £8,500 and ordered to pay costs of £1,500 at Haverfordwest Magistrates' Court following a prosecution brought by the Health and Safety Executive (HSE).
The court heard Mr Douglas-Law's tenant had originally raised a complaint with Pembrokeshire County Council environmental health officers over cold and damp conditions at the property.
On viewing the conditions at the property, council officers served Mr Douglas-Law an Improvements Notice under the Housing Act and reported concerns about the condition of the gas appliances to the HSE.
A HSE investigation discovered he had failed to maintain the gas fire in a safe condition, as well as failing, over a period of six years, to ensure the appliance was checked for safety every 12 months.
While no injuries were sustained, Mr Douglas-Law's tenant and her son were prompted to visit the hospital to check for exposure to carbon monoxide (CO) after an alarm at the property indicated a high CO reading.
In summing up today, the magistrate said Mr Douglas-Law had been extremely lucky that no harm had come to his tenants.
David Ian Douglas-Law, 63, of Penally, Tenby, pleaded guilty to breaching regulations 36 (2), 36 (3) (a), 36 (3) (b) and 36 (4) of the Gas Safety (Installation & Use) Regulations 1998. He was fined a total of £8,500 and ordered to pay costs of £1,500, plus a £15 victim surcharge.
Read comments from HSE inspector Stephen Jones and Paul Johnston, chief executive of Gas Safe Register.