How Markham is built
- Before 1961 3%
- 1961–1990 38%
- 1991–2000 17%
- 2001 or later 43%
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 Markham homes
In the Toronto area, the main heating energy is natural gas for 52% of households (Statistics Canada, 2023). Any fuel-burning appliance, fireplace or attached garage is a potential CO source.
Single-detached houses make up 56% of Markham'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 Markham
Communities served
Markham's page covers the whole City of Markham, including Locust Hill and Unionville.
The organizations and professionals listed for Markham may or may not travel to every community, so ask when you call.
Area guide for the surrounding region, with every town and hamlet listed: York Region area guide (Newmarket, Aurora, Stouffville, Georgina and more).
Carbon monoxide testing in Markham: common questions
Are carbon monoxide alarms mandatory in Markham?
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.