Aberdare contractor Ken Parry pleaded guilty to carrying out work while not Corgi registered and making false entries on landlords' gas safety records.
 
Parry, and his company Ken Parry Heating and Construction, were served with prohibition notices by HSE in January 2005 as a result of an investigation into gas fitting work undertaken, where there was a spillage of combustion products from the appliances concerned.
 
However Parry had been carrying out work across South Wales since the issue of the prohibition notice.
 
HSE inspector Hugh Emment said: "While gas appliances which are correctly fitted and maintained are extremely safe, incorrectly fitted or poorly maintained appliances can give rise to carbon monoxide which is odourless, colourless and can result in illness or death.
 
"This case also provides a salutary warning for anyone doing gas work without the correct training or registration - HSE will take the strongest action possible against anyone who does not comply with the law. Their behaviour is putting lives at risk."