“The carbon monoxide in Lindvig’s shop came from a natural gas heater. Lindvig told the Tribune that he called a technician who said the gas buildup likely was due to an issue with the chimney…he had taken detectors in his home that were about to reach the end of their lifespan and put them out in the shop, and they had enough life left to alert him and his wife…”

Bismarck couple’s close call, other incidents renew attention on carbon monoxide dangers | State & Regional | bismarcktribune.com