The house is getting cold and the furnace is not doing anything. Before you call, a few checks take five minutes and sometimes fix it. Some situations, though, mean stop checking and get out. This guide covers both, for homeowners in Toronto and the GTA.
Stop first: gas smell or a CO alarm
If you smell gas, leave the house right away, do not touch light switches, and call 911 from outside. Then call Enbridge's emergency line at 1-866-763-5427.
If a carbon monoxide alarm sounds, Health Canada's advice is to get everyone out immediately, not to try to find the source, to call 911, and to go back in only after a professional has fixed the problem. None of the checks below apply in either case.
The Ontario CO alarm rule
Since January 1, 2026, Ontario's Fire Code requires a working carbon monoxide alarm on every storey of a home that has a fuel-burning appliance (a furnace, water heater or gas stove), a fireplace or an attached garage. That includes storeys with no bedrooms. There must also still be an alarm next to sleeping areas. Test alarms monthly and replace them on the manufacturer's schedule. Details are at Ontario.ca.
Five safe checks
- The thermostat. Confirm it is set to Heat, and turn it up a few degrees above the room temperature. If it takes batteries, replace them.
- The power. Most furnaces have a switch that looks like a light switch, on or near the unit. Check that it is on, then check the breaker or fuse.
- The filter. Turn the furnace off at the switch, pull the filter and look at it. If it is packed with dust, replace it before restarting. Natural Resources Canada says to change or clean forced-air filters every three months or when they are loaded.
- The vents. Look at the outdoor intake and exhaust pipes on a high-efficiency furnace and clear snow or ice with a soft broom, as Enbridge recommends after every storm. Check indoor vents and registers are open. If the gas meter is iced over, call Enbridge rather than breaking the ice yourself.
- The gas shut-off and pilot. Confirm the shut-off valve at the furnace has not been knocked closed. If your furnace has a standing pilot light, relight it only by following the owner's manual. If it will not stay lit, or you are unsure at any step, stop.
If the furnace starts and the house warms up, you have saved a service call. Most modern furnaces light with an electronic ignitor rather than a pilot, and the ignitor and flame sensor are inside the cabinet. Leave the panels closed. Pulling them off is how a dead furnace becomes a gas or electrical hazard.
Stop and call a licensed gas technician when
- The furnace clicks or starts up, then shuts off, or keeps starting and stopping.
- The flame is yellow or flickering instead of steady blue, or you see soot around the unit.
- There is water around the furnace, or the plastic drain line or vent pipe looks frozen. Turn the furnace off and call. Do not try to thaw it yourself. Manufacturer manuals note that frozen condensate blocks drains and shuts the furnace down.
- Nothing above fixed it, or you are not sure what you are looking at.
In Ontario, gas appliance work should be done by a TSSA-certified gas technician. Enbridge does not repair furnaces; it points customers to a registered HVAC contractor and suggests verifying TSSA registration.
What to tell us when you call
- The furnace brand and roughly how old it is.
- What it did: silent, clicking, blowing cold air, or starting and stopping.
- What you already checked, and any blinking light or code on the control board.
- Who is in the house. Infants, seniors and anyone with a medical condition change how urgent it is.
Quotes by phone are free, and in-person inspections start at $150. Call (647) 852-2359 or see our furnace repair page. We work across Toronto and the GTA, including North York and Scarborough.
Once it is running again
Enbridge recommends an annual inspection by a licensed contractor before the heating season, and it is the best way to stop a repeat. Our furnace maintenance page covers what is included. If the furnace keeps failing, our furnace replacement cost guide shows what other installers publish and when replacing starts to make sense.