At Haddington Sheriff Court, in East Lothian, John Martin Riva was fined £15,000 after pleading guilty to a contravention of Sections 3 and 33 (1) of the Health and Safety at Work Act 1974.
The case was brought by the Crown Office and Procurator Fiscal Service, which has sole responsibility for raising criminal proceedings for breaches of health and safety legislation in Scotland.
The court heard how Riva, having been contracted to rebuild the chimney on a property in Gifford in August 2009, failed to ensure that it was fully cleared of any debris and masonry materials that had fallen in. The chimney was thus left blocked when the fire in the living room of the house was brought into use by the Ross family who lived there.
The blockage impeded the combustion process of the solid fuel fireplace in the living room, and caused the fumes from the fireplace to build up, causing an accumulation of carbon monoxide to which the three occupants of the house were exposed
Mrs Ceridwen Ross, aged 60 years, died on 26 October 2009 as a result of the exposure.
Following the case, Elaine Taylor, Head of the COPFS Health and Safety Division, said: "This case demonstrates yet again the importance of employers and contractors being aware of the risks not only to their own employees, but to all of those who may be affected by the work they carry out.
"If Riva had taken the simple steps necessary to identify the risks associated with his work and acted upon them, Mrs Ross would not have lost her life in an entirely avoidable incident.
"Today our thoughts are with her family."
HSE Inspector Gillian McLean said: "This was a tragic incident which could easily have been prevented if the accused had carried out simple and well-established tests to ensure the chimney was free from obstruction following building work he had carried out.
"These are standard and recognised tests well known to the building industry and we hope this successful prosecution will draw attention to these tests to ensure workers carry them out in the future in order to avoid similar devastating consequences."