Furnace Red Tag in Ontario: What It Means and What Happens Next
Written by the Northland Home Comfort team — TSSA-registered heating, cooling and hydronics contractor (FS-R-50021) serving Simcoe County and Muskoka. Updated October 2026.
Short answer: A red tag in Ontario means a licensed gas technician found a condition on a gas or propane appliance that is unsafe under the Technical Standards and Safety Act and has tagged it under TSSA rules. A Type A (immediate hazard) tag means the appliance is shut off and the gas supply to it disconnected on the spot — it cannot be used until repaired or replaced. A Type B (non-immediate hazard) tag means it can keep running for a limited time, stated on the tag and typically 30 days, after which the gas supplier can shut it off if it is not fixed. The most common red-tag causes are cracked heat exchangers, venting problems, gas leaks and carbon monoxide readings.
Why appliances get red-tagged
- Cracked or corroded heat exchanger on a furnace: combustion gases can enter the house air. The most common reason an older furnace is tagged.
- Carbon monoxide in the flue gas or the house above safe limits.
- Venting defects: disconnected, corroded or improperly sized vent pipes, or a blocked chimney.
- Gas leaks at valves, unions or piping.
- Improper installation or clearances, including unapproved conversions and missing shutoffs.
- Water heater and boiler issues: backdrafting, flame rollout, failed safeties.
Type A vs Type B
| Type A: immediate hazard | Type B: non-immediate hazard | |
|---|---|---|
| What the tech does | Shuts the appliance down, disconnects or caps the gas, applies the tag | Applies the tag; appliance may run while you arrange repair |
| Can I use it? | No | Yes, for the period on the tag |
| Deadline | Immediate | Typically 30 days; the tag states it |
| Who is notified | The gas distributor (Enbridge or your propane supplier) | The gas distributor |
| If not fixed | Stays off | Supplier can lock the meter or stop delivery |
The technician is required by law to tag the appliance and notify the distributor. They cannot be talked out of it, and a second company cannot simply remove a tag without correcting the problem.
What to do when your furnace is red-tagged
- Ask for the specifics. The tag and the report should state the exact defect. Cracked heat exchanger, CO reading, venting — the fix depends on it.
- Get a second opinion if it feels wrong. You can have another licensed contractor inspect. If there is a genuine crack, any honest technician will find the same thing. We do these inspections and show you the crack on camera.
- Repair or replace. A heat exchanger on a furnace over ten years old is usually not worth replacing; the part plus labour approaches a new furnace. Venting, valve and sensor defects are normally repaired.
- Get heat back. For a Type A tag on a furnace in winter, same-day or next-day replacement is the usual answer. Our no-heat line is 705-321-9456.
Getting the tag cleared
Once the defect is corrected by a licensed technician, the technician documents the repair or replacement and the distributor is notified so gas service continues. A new furnace is installed under permit with a TSSA inspection; that closes the file.
Avoiding a red tag
Annual service catches venting, CO and heat exchanger problems before they become tags. Furnaces over 15 years old with a history of overheating or short cycling are the ones most at risk. See furnace short cycling and how much a new furnace costs.
If you ever smell gas or a CO alarm sounds: leave the house, call 911 from outside, and for natural gas call Enbridge at 1-866-763-5427. Our emergency page has the steps.
Frequently asked questions
A licensed gas technician found an unsafe condition and tagged the appliance under TSSA rules. Type A means it is shut off immediately; Type B means it can run for a stated period, typically 30 days, while the defect is fixed.
No. The tag can only be cleared by a licensed technician after the defect is corrected, and the gas distributor is notified. Running a Type A tagged appliance is illegal and dangerous.
The period is written on the tag, typically 30 days. After that the distributor can lock the meter or stop propane delivery until the repair is done.
Rarely on a furnace over ten years old. The part is expensive and the furnace is near the end of its life anyway. Replacement is usually the better value and gets you a warranty.
Yes, as long as they are licensed and correct the actual defect. What they cannot do is remove the tag without fixing the problem.
Red-tagged furnace, boiler or water heater? Call 705-321-9456. We will confirm the defect, give you repair and replacement prices in writing, and get the heat back on.
