Hardwired smoke and CO alarms: what homeowners should know

Why hardwired and interconnected matters

A smoke alarm is only useful if someone hears it in time. In a two-storey home with a developed basement, an alarm going off downstairs can be almost silent in a closed bedroom upstairs.

That is why newer homes have hardwired, interconnected alarms. They are powered by a household circuit, have a battery backup for outages, and are linked so that when one detects smoke, every alarm in the house sounds.

Carbon monoxide (CO) alarms matter just as much in Edmonton. Furnaces, gas water heaters, fireplaces and attached garages are all potential CO sources, and in winter our homes are sealed up tight with the heat running for months.

Where alarms belong

Requirements depend on when your home was built and what work has been done since. Current Alberta building rules for new homes generally call for smoke alarms on every storey including the basement, in each bedroom, and in the hallway or area outside sleeping rooms, all interconnected. Homes with a fuel-burning appliance or an attached garage also need CO alarms. For the exact rules that apply to your home or project, check with the permit authority.

• Mount smoke alarms on the ceiling or high on a wall, following the manufacturer's instructions.
• Keep them away from bathroom doors, cooking appliances and heating vents, where steam, cooking fumes and air flow cause false alarms or delays.
• Place CO alarms where the manufacturer recommends, usually near sleeping areas so they can be heard at night.
• Combination smoke and CO alarms save ceiling space and wiring in many homes.

How interconnection works

Hardwired alarms on the same system share power from a circuit in your panel, plus an extra interconnect conductor that carries the signal from one alarm to the rest. Some newer systems link alarms wirelessly instead, which can help in finished homes where running new cable is difficult.

Most interconnected alarms only work with the same brand and family of units. When one fails, the replacement usually has to be compatible with the others, or the whole set needs replacing.

Testing and replacing

Test every alarm monthly with its test button. On an interconnected system, pressing test on one alarm should make all of them sound. If one stays quiet, it is not connected properly or it has failed.

• Smoke alarms should be replaced 10 years from the manufacture date printed on the back.
• CO alarms have their own lifespan, often 7 to 10 years. Check the label on yours.
• A regular chirp usually means a low battery or an end-of-life warning. Check the manual for what the pattern means.
• Vacuum dust from the vents gently, as the manufacturer recommends.

Upgrading an older home

Many older Edmonton homes still rely on battery-only alarms, or on a few hardwired units that are not interconnected. Upgrading is very worthwhile, especially if you have a developed basement, a basement suite or bedrooms on more than one floor.

Options include running new cable for hardwired interconnected alarms, which is easiest during a renovation, or using alarms that link wirelessly while still being hardwired for power at each location. A licensed electrician can tell you what makes sense for your layout.

If you are developing a basement, adding a suite or doing a major renovation, alarm requirements are typically part of the permit and inspection. That is a natural time to bring the whole house up to date. See our basement renovations service and renovation electrical safety guide.

If an alarm goes off

• Smoke alarm: get everyone out, stay out and call 911 from outside.
• CO alarm: get everyone outside into fresh air and call 911 or your gas utility's emergency line. Do not go back in until it has been checked.
• False alarms from cooking or steam: ventilate and use the hush button if your unit has one. If false alarms keep happening, the alarm may be in the wrong spot or near the end of its life.

Common questions