Working smoke alarms on every storey and outside sleeping areas are required in Ontario homes, and carbon monoxide alarms are required near bedrooms in any home with a fuel-burning appliance, a fireplace, or an attached garage. As of January 1, 2026, Ontario's Fire Code expanded the CO requirement: alarms adjacent to each sleeping area and on every storey, including storeys without bedrooms. BC has parallel rules.
$30 to $100 per device DIY; ~$150 to $300 per hardwired device installedAddress immediatelyInterior
The quick answer
Working smoke alarms on every storey and outside sleeping areas are required in Ontario homes, and carbon monoxide alarms are required near bedrooms in any home with a fuel-burning appliance, a fireplace, or an attached garage. As of January 1, 2026, Ontario's Fire Code expanded the CO requirement: alarms adjacent to each sleeping area and on every storey, including storeys without bedrooms. BC has parallel rules.
This is the cheapest life-safety item in a house, and a surprisingly good tell. A home with missing, yellowed, or painted-over alarms is telling you something about how everything else was maintained. Alarms also expire: the replace-by date on the back is typically 10 years from manufacture.
How to spot it
Look at the hallway ceiling outside the bedrooms and on each floor, including the basement. Yellowed housings, paint on the unit, or a missing base plate all mean "replace." Check for a CO alarm near sleeping areas in any home with gas appliances, a fireplace, or an attached garage.
What it costs
$30 to $100 per device DIY; roughly $150 to $300 per device for hardwired replacements installed by an electrician.
What to do
Immediately on moving in, install fresh combination smoke/CO alarms wherever required, whatever the sellers had. It's the cheapest line item of the entire move.
Education and triage, not a home inspection. Placement requirements are fire-code specifics that vary by province and dwelling type, Casaroo notes what's visible; your local fire service or inspector confirms what's required.
Common questions
What is Smoke & carbon monoxide alarms?
Working smoke alarms on every storey and outside sleeping areas are required in Ontario homes, and carbon monoxide alarms are required near bedrooms in any home with a fuel-burning appliance, a fireplace, or an attached garage. As of January 1, 2026, Ontario's Fire Code expanded the CO requirement: alarms adjacent to each sleeping area and on every storey, including storeys without bedrooms. BC has parallel rules.
Why does it matter for home buyers?
This is the cheapest life-safety item in a house, and a surprisingly good tell. A home with missing, yellowed, or painted-over alarms is telling you something about how everything else was maintained. Alarms also expire: the replace-by date on the back is typically 10 years from manufacture.
How can I spot it?
Look at the hallway ceiling outside the bedrooms and on each floor, including the basement. Yellowed housings, paint on the unit, or a missing base plate all mean "replace." Check for a CO alarm near sleeping areas in any home with gas appliances, a fireplace, or an attached garage.
How much does it cost to fix?
$30 to $100 per device DIY; roughly $150 to $300 per device for hardwired replacements installed by an electrician.
Last reviewed 2026-07-10.
This guide is general education, not a home inspection and not advice for your specific property. Always
consult the appropriate licensed professional, and get a licensed home inspection before you remove conditions
or buy. Cost ranges are 2026 estimates that vary by region, size, and access; confirm specifics with a
qualified professional.