The Plumbers, Gasfitters & Drainlayers Board says unlicensed operators repairing chimneys damaged by the Canterbury earthquake could be putting lives at risk.
The organisation licences plumbers, gasfitters and drainlayers.
It says unlicensed building companies could be accidentally altering the venting systems for gas fires when they fix chimneys.
The board says that can cause toxic gasses like carbon monoxide to leak into the house.
It says fixing chimneys can be a highly technical job and it is illegal to do gasfitting work without a license.
Residents are urged to make sure the person fixing their chimney is licensed.
