A bird's nest which partially blocked a chimney led to a man dying of carbon monoxide poisoning from a coal fire, an inquest has heard.
Christopher Joseph Hegarty, 19, a trainee mechanic died after falling asleep in the living room of his home in Castlederg on 2 April, 2004.
The Coroner's Court in Limavady heard Mr Hegarty's father found him dead.
He became worried when he could not contact his son and let himself into his house with a spare key.
Mr Hegarty lit a fire in his living room and fell asleep, the inquest heard.
A witness from the Coal Advisory Board said he had not seen a similar fatality caused by an open fire in 30 years.