Firefighters are warning people not to keep ash from wood-burning stoves inside because of the danger of carbon monoxide (CO) poisoning.
It follows an incident in Newton Abbot on Saturday when a CO alarm went off, but the log burner had "zero readings".
Crews discovered the colourless, odourless and tasteless gas was coming from a bucket of ash in the lounge.
Embers in the bucket gave off potentially-lethal readings of 378 parts per million (ppm).
Health effects from exposure to CO levels of approximately 1 to 70 ppm are uncertain, but as levels increase and remain above 70 ppm, symptoms including headaches, fatigue and nausea will become more noticeable and can become life-threatening within three hours.
"The occupier empties the old ash from the log burner into the bucket regularly but does not take it outside until its full," the brigade said on its Facebook page.
"The embers were producing CO into the lounge which caused the CO alarm to sound - luckily for this person they had an alarm."