CO Alarm Going Off? What to Do About Your Furnace

If your carbon monoxide alarm is sounding its alarm pattern, get everyone, pets included, out of the house now. From outside, call 911 or FortisBC at 1-800-663-9911. Don’t go back in until the fire department or FortisBC says it’s safe, and don’t run the furnace again until it has been checked.

Steps Right Now

1. Get everyone and every pet outside.
2. Call 911 or FortisBC at 1-800-663-9911 (24 hours) from outside.
3. If anyone has a headache, nausea, drowsiness or feels confused, tell the 911 operator and get medical help.
4. Stay out until the responders say it’s safe.
5. Leave the furnace off until a licensed gas fitter has checked it.

These steps follow FortisBC’s carbon monoxide guidance. FortisBC also notes that if several people feel the same symptoms, or feel better once they leave the house, it could be CO.

Alarm or Low-Battery Chirp?

Most CO alarms make two different sounds. A loud repeating alarm pattern means the alarm detected CO: treat it as real. A single chirp every minute or so usually means a low battery or an alarm at the end of its life. The pattern for your model is printed on the back of the alarm or in its manual. If you can’t tell which one it is, treat it as an alarm and go outside.

How a Gas Furnace Can Produce Carbon Monoxide

A gas furnace makes some carbon monoxide when it burns gas. The venting carries those gases outside, and the heat exchanger keeps them separate from the air you breathe. CO gets into the house when one of those fails:

• Blocked venting. A bird’s nest, a disconnected pipe, or snow and ice over the plastic pipes on a high-efficiency furnace.
• Poor combustion. Dirty burners or the wrong gas pressure can make the flame produce more CO.
• A cracked heat exchanger. See heat exchanger problems.
• Another appliance. The water heater, gas fireplace, gas range or a car running in an attached garage can also set off the alarm.

What David Checks After an Alarm

Once the emergency responders have cleared the house, David checks the furnace and the other gas appliances: the venting from end to end, the burners and flame, the gas pressure, the heat exchanger where he can see it, and the CO level at the furnace while it runs. You get his findings and the repair price before any work starts.

Where CO Alarms Should Go

FortisBC recommends a CO alarm in or just outside each sleeping area and on each level of the home. Test them, and if yours runs on batteries, check them at least twice a year. Most alarms have an end-of-life date printed on them.

Questions About CO Alarms and Furnaces

What should I do if my carbon monoxide alarm goes off?

Get everyone and every pet outside, then call 911 or FortisBC at 1-800-663-9911 from outside. Stay out until responders say it is safe, and leave the furnace off until a licensed gas fitter has checked it.

Can a gas furnace cause carbon monoxide?

Yes, if the venting is blocked or disconnected, the combustion is poor, or the heat exchanger is cracked. Other gas appliances and a car in an attached garage can also be the source.

My CO alarm is chirping once a minute. Is that CO?

Usually not. A single chirp often means a low battery or an alarm at the end of its life. A loud repeating pattern means it detected CO. If you are not sure, go outside and call.

Can SkyLimit check my furnace after a CO alarm?

Yes, once 911 or FortisBC has cleared the house. Call 778-892-5119. We work Monday to Saturday, 9 AM to 9 PM, and do not run a 24-hour line.