Here’s why you want a carbon monoxide detector in your home. In Elliot Lake the three CO alarms went off in a house and an inspection of the readings show they were at life threatening levels. Firefighters evacuated the homeowners and the source of the deadly gas was traced to the furnace. The unit was shut down until it could be fixed. In Ontario it’s now the law that homes with gas-burning appliances need to be equipped with CO alarms.