Do Carbon Monoxide Detectors Need a Dedicated Circuit?

Do Carbon Monoxide Detectors Need a Dedicated Circuit?

Carbon monoxide detectors do not require a dedicated circuit. They can be plug-in units, battery-powered units, or hardwired units that share a circuit with other loads. The important requirements in Ontario are where they are installed and that they are kept functional. Here is what you need to know.

Ontario Carbon Monoxide Detector Requirements

Under the Ontario Fire Code, carbon monoxide alarms are required in residential occupancies that contain:

• A fuel-burning appliance (natural gas furnace, gas water heater, gas stove, wood-burning fireplace, etc.)
• An attached or built-in garage
• A fuel-burning fireplace of any type

Where required, a CO alarm must be installed adjacent to each sleeping area. In newer construction requiring a building permit, CO alarms must be hardwired and interconnected — the same standard as smoke alarms.

Plug-In vs Battery vs Hardwired CO Alarms

• Plug-in — plugs into a standard outlet; most include a battery backup. These satisfy the Fire Code requirement for existing homes and do not require electrical work.
• Battery-only — acceptable for existing homes; the battery must be maintained and replaced as needed. Some jurisdictions recommend sealed 10-year lithium battery units to reduce maintenance.
• Hardwired — connects to the home’s electrical system on a shared circuit; uses battery backup during outages. Required in new construction and renovations requiring a building permit. These do not need a dedicated circuit — they can share a circuit with lighting or other loads.

Combination Smoke and CO Alarms

Combination smoke and carbon monoxide alarms are permitted under the Ontario Fire Code and Building Code and satisfy both requirements with a single device. These are available in both battery and hardwired configurations and can simplify installation in homes where both types of detection are required in the same location.

How Often Should CO Alarms Be Replaced?

The electrochemical sensing cell in a CO alarm has a limited lifespan — typically 5 to 7 years. Replace CO alarms according to the manufacturer’s end-of-life date printed on the unit, regardless of whether the alarm is still responding to test. An alarm that passes the test button check but has an expired sensor may not reliably detect CO.

EZSMART installs hardwired, interconnected smoke and CO alarm systems for residential and commercial properties across Ontario. Contact us if your building permit requires hardwired alarm installation.

Amir Azimipour

Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp