Carbon Monoxide Alarms: Where to Install and What to Do

Carbon monoxide (CO) is a colourless, odourless gas produced when fuel such as natural gas, propane, oil or wood doesn't burn completely. A cracked furnace heat exchanger, a blocked chimney or vent, or a car left running in an attached garage can fill a home with CO without anyone noticing. A working CO alarm is the only reliable way to know. Since 2014, Ontario law has required CO alarms in homes with a fuel-burning appliance, a fireplace or an attached garage.

Early symptoms feel like the flu without a fever: headache, dizziness, nausea, tiredness and shortness of breath. Warning signs are several people (or pets) in the home feeling unwell at the same time, and feeling better after leaving the house. High levels cause confusion, loss of consciousness and death, and the danger is greatest at night while people are asleep.

Under the Ontario Fire Code, homes with a fuel-burning appliance, fireplace or attached garage must have a CO alarm installed outside every sleeping area. For extra protection, put one on every storey, including the basement near the furnace room, following the distance from fuel-burning appliances that the manufacturer recommends. Follow the manufacturer's instructions for mounting height. Landlords are responsible for installing and maintaining CO alarms in rental units, and tenants must tell the landlord if one is not working.

CO alarms cost about CAD $30–$60 each, and combination smoke and CO alarms about CAD $50–$80. Choose alarms certified to the Canadian standard (look for a CSA or ULC mark). Plug-in models should have a battery backup. You may also need a drill, screwdriver and wall anchors for mounting, and fresh batteries.

1. Check that you have a CO alarm outside every sleeping area, and add any that are missing.
2. Press and hold the test button on each alarm monthly until it sounds.
3. Replace batteries at least once a year, or whenever an alarm chirps for low battery. A good reminder is when the clocks change.
4. Check the manufacture or replace-by date on the back of each alarm. Most CO alarms wear out after 7 to 10 years, and many give an end-of-life signal; replace them when they reach that date.
5. Read the label on each alarm so everyone in the house knows the difference between the full alarm pattern and the low-battery or end-of-life chirp.
6. Gently vacuum the alarm vents to keep dust out.
7. Book a yearly inspection of your furnace, water heater, fireplace and venting by a qualified technician.

Treat every full alarm as an emergency. Get everyone, including pets, outside into fresh air right away and do not stop to open windows. Call 911 from outside, even if no one feels sick. Do not go back inside until firefighters say it is safe. If firefighters find CO, do not use the furnace or other fuel-burning appliances again until a TSSA-registered technician has inspected and repaired them.

Call a TSSA-registered gas technician to inspect fuel-burning appliances after any CO alarm, if you see soot or yellow flames, or if your furnace or water heater has not been serviced in over a year. Hardwired and interconnected alarms should be installed by a licensed electrician.