Steven Poole, who has since died, often fitted flue connections incorrectly and failed to supply and fit carbon monoxide detectors.
At Haverfordwest Magistrates' Court before his death, he admitted regularly breaching legal requirements.
The council said the burners should be checked as they could be dangerous.
The council said Poole, of Johnston, who traded as SM Poole, also falsely claimed he had correctly carried out the installation and that his work met Hetas (Heating Equipment Testing and Approval Scheme) safety requirements.
Cllr Huw George, cabinet member for environmental and regulatory services, said the council was "very concerned that there could be several hundred incorrectly fitted stoves in the county, which may very likely be unsafe".
Hetas said any stoves fitted by Mr Poole should be tested to ensure they are safe to use.
It has written to 500 people warning them to get their burners checked, but the council said it was not convinced many people had responded.
"We are concerned that a significant number of people may not have responded to the letters and we urge anyone affected to contact Hetas without delay," Mr George added.
Hundreds of homes in Pembrokeshire could have had wood or coal burners fitted incorrectly leaving them "unsafe", the council has said.