An 80-year-old man died of carbon monoxide poisoning, while his wife was taken to hospital, the day after the flue of the device was cleaned.
Robert Sinclair, a retired law lecturer from County Antrim, Northern Ireland, died after succumbing to the effects of the toxic gas in his home.
A chimney sweep had cleaned the flue of the couple's coal burning boiler the day before the incident and it is believed the flue had then become blocked.
While Mr Sinclair's wife was rushed to hospital with chest pains and headaches - which were not immediately linked to carbon monoxide poisoning - Mr Sinclair fell ill and then died later.
Carbon monoxide poisoning can be difficult to detect as its symptoms - headaches, nausea, vomiting and fainting - are similar to other more common illnesses.
Coroner Brian Sherrard said that homeowners should be wary after having their boiler flues cleaned and ensure they remain vigilant over the following days to make sure that they do not become ill.
