How London is built
- Before 1961 25%
- 1961–1990 41%
- 1991–2000 11%
- 2001 or later 24%
The rule in Ontario
Ontario's Fire Code requires CO alarms in existing homes that have a fuel-burning appliance, a fireplace or an attached garage: next to every sleeping area and, since January 1, 2026, on every storey as well.
Where CO alarms go: installation rules in Ontario
What the rules say about installing alarms:
- Required in every home with a fuel-burning appliance, a fireplace or an attached garage, and since January 1, 2026 also in homes served by a forced-air fuel-burning appliance located outside the building.
- Put an alarm next to each sleeping area and, since January 1, 2026, on every storey that has no sleeping area.
- Hardwired, battery and plug-in alarms are all allowed.
- The homeowner is responsible in an owner-occupied home, and the landlord in a rental.
- For new houses, the National Building Code 2020 (Article 9.32.3.9) requires a CO alarm inside each bedroom or within 5 m outside each bedroom door when the home has a fuel-burning appliance or an attached garage, an alarm in any room with a solid-fuel-burning appliance (on or near the ceiling unless the maker's instructions say otherwise), and interconnected alarms in a house with a secondary suite.
CO sources in London homes
In the London area, the main heating energy is natural gas for 61% of households (Statistics Canada, 2023). Any fuel-burning appliance, fireplace or attached garage is a potential CO source.
Single-detached houses make up 49% of London's households; many have an attached garage, another reason to put an alarm near the door into the house.
What a CO check involves
- Alarms next to sleeping areas and on every storey, tested monthly and replaced by their end-of-life date (usually 7 to 10 years).
- Annual service of fuel-burning appliances by a licensed technician.
- A combustion spillage test during an energy evaluation, which catches a venting problem before it produces CO.
Our carbon monoxide guide · Combustion safety testing in London
Carbon monoxide testing in London: common questions
Are carbon monoxide alarms mandatory in London?
Ontario's Fire Code requires CO alarms in existing homes that have a fuel-burning appliance, a fireplace or an attached garage: next to every sleeping area and, since January 1, 2026, on every storey as well.
Where should CO alarms go in Ontario?
Required in every home with a fuel-burning appliance, a fireplace or an attached garage, and since January 1, 2026 also in homes served by a forced-air fuel-burning appliance located outside the building. Put an alarm next to each sleeping area and, since January 1, 2026, on every storey that has no sleeping area. For new houses, the National Building Code 2020 (Article 9.32.3.9) requires a CO alarm inside each bedroom or within 5 m outside each bedroom door when the home has a fuel-burning appliance or an attached garage, an alarm in any room with a solid-fuel-burning appliance (on or near the ceiling unless the maker's instructions say otherwise), and interconnected alarms in a house with a secondary suite.
How long do CO alarms last?
Most have an end-of-life date of 7 to 10 years printed on the unit; replace them by then even if they still beep when tested.