At least two people have been treated in hospital, after a potentially deadly gas flooded through their south east Cornwall home.
But their lives may have been saved by a carbon monoxide detector.
A fire crew from Polruan was called to the alarm sounding at Lanteglos on Wednesday night.
A spokesperson for Cornwall Fire and Rescue Service said: “At 1930 this evening Cornwall Fire and Rescue Service were called to a Carbon Monoxide detector sounding.
“One crew from Polruan and an Officer attended. The crew made the property safe and ventilated.
“West Country Ambulance Service also attended. The occupants of the property have attended hospital.”