Smoke and carbon monoxide alarms are the most-installed and most-misunderstood pieces of safety equipment in Ontario homes. The Ontario Fire Code (OFC) and the OESC have specific requirements about where alarms go, what kind of alarms they must be, and how they have to be interconnected. Most homeowners assume they comply; most homes actually do not. Here is what the rule actually says.
The Ontario smoke alarm rule
The Ontario Fire Code requires smoke alarms in every dwelling unit in the following locations:
- One smoke alarm on every storey of the home
- One smoke alarm in every sleeping area
- One smoke alarm in every hallway leading to sleeping areas
Alarms must be either hardwired (with battery backup) or 10-year sealed lithium battery type. For new construction and major renovations, the OESC requires alarms to be hardwired AND interconnected - meaning when one alarm sounds, every alarm in the home sounds. The reason: a smoke alarm sounding in the basement does no good if the residents in the upstairs bedrooms cannot hear it.
The CO alarm rule
Carbon monoxide alarms are required in any home that has a fuel-burning appliance (gas furnace, propane furnace, oil furnace, gas water heater, gas stove, gas fireplace, wood stove) or an attached garage. Locations:
- Within 5 metres of every sleeping area
- On every storey containing a fuel-burning appliance or that is adjacent to an attached garage
CO alarms must be CSA 6.19 certified. Many homeowners use combination smoke/CO alarms, which is allowed and convenient - one device, two functions.
Interconnection - the part most homes get wrong
For homes built or substantially renovated after 2006 (the rule date varies a bit by jurisdiction), the OESC requires alarms to be interconnected. The interconnection can be:
- Hardwired interconnection - a third wire (the "interconnect" lead) ties every alarm together so they all sound simultaneously. This is the standard for new construction.
- Wireless interconnection - newer alarms (Kidde Wireless, BRK SC9120B-WiFi, Nest Protect) can interconnect over radio without running new wire. Useful for retrofits where running new wire would mean opening drywall.
If you have hardwired alarms that don't sound together when one is triggered, the interconnect lead is either not landed or not present. We see this often during electrical inspections - the alarm wiring runs to every device but the interconnect was never connected.
What needs to change in older homes
The OFC's smoke alarm location rules apply to every home in Ontario, regardless of age. The hardwiring and interconnection requirement only applies to construction and renovation built after the rule came into force. So an older home that has battery-only alarms in the right locations is code-compliant; an older home missing alarms in any required location is not.
If you are renovating a home built before the hardwiring rule came in, the renovation itself may trigger the requirement to upgrade alarms in the renovated portion. The municipal building department or your renovation electrician will tell you.
10-year sealed lithium alarms - the easy path for retrofits
Battery-replacement alarms have a real failure mode: nobody changes the batteries. A 10-year sealed lithium alarm (Kidde Worry-Free, First Alert SA710CN, BRK SC7010BV) eliminates the battery-changing chore for a decade - the battery is sealed inside, you install the alarm, and you replace the whole unit in year 10. For older homes that do not have hardwired alarms, this is the practical retrofit path.
Important caveat: 10-year sealed alarms are NOT interconnected. If your jurisdiction requires interconnection (new construction or major reno), you need hardwired or wireless-interconnected alarms.
Common mistakes we find
- Alarm in the kitchen. Nuisance trips from cooking. The OFC actually prohibits ionization-type alarms within 6 feet of cooking equipment for this reason. Photoelectric alarms tolerate cooking better; even better, place the alarm in the hallway outside the kitchen.
- Alarm in the bathroom or beside the shower. Steam triggers the alarm. Move it outside the bathroom door.
- Alarms wired but interconnect never landed. Common in homes wired by less-experienced electricians. We test the interconnect on every safety inspection.
- CO alarm missing or in the wrong place. CO alarms are the most-forgotten device. They are required in homes with fuel-burning appliances, and the location rules are specific.
- Alarms past their service life. Smoke alarms expire (typically 10 years from manufacture date). CO alarms typically 7-10 years. Check the date on the back of every alarm in your home.
What we install
For new builds and major renovations: BRK SC7010B series (hardwired smoke+CO combo with battery backup), wired and interconnected per the OESC. For retrofits: Kidde or BRK 10-year sealed wireless-interconnect alarms where running new wire is not practical, or hardwired retrofits where the wiring is accessible. For luxury homes that want smart integration: Nest Protect (the integration story is good, the unit cost is higher).
When to call us
If you are not sure whether your home complies with current code, or you are planning a renovation and the contractor is asking about alarm requirements, request a safety inspection. We document the current state, identify any compliance gaps, and quote the corrections. ESA permit and Certificate of Inspection if any new wiring is involved - and if the work overlaps with a panel upgrade we can roll it into the same visit.