What a Red Tag on Your Furnace or Water Heater Means in Ontario

Short answer: A red tag means your furnace or water heater was found unsafe or out of code. In Ontario, Enbridge Gas uses two levels: an immediate hazard, where gas is shut off right away, and a lesser violation, where you have up to 42 days to repair or replace. Either way, hire a TSSA-registered contractor.

If you smell gas, stop reading

Leave the building right away, leaving the door open behind you if you can do it without delay. Once you're outside and away from the house, call the Enbridge Gas 24-hour emergency line at 1-866-763-5427, or dial 911. Don't turn lights or appliances on or off, don't use your phone inside, and don't assume someone else has already called.

What a red tag is

When a gas utility technician or a gas contractor finds a problem with a gas appliance, they attach a tag to it and give you written notice. The tag records what's wrong and how serious it is. It's there to protect you and anyone who works on the appliance after.

Common reasons include venting problems, signs of spillage of exhaust gases, a cracked or damaged part, a gas leak, or an installation that doesn't meet code.

The two levels of red tag

Enbridge Gas describes two categories of safety violation:

The wording on your notice may differ, but the key point is the same: a Category B tag is not optional, and the clock is running.

What you should never do

• Don't remove the tag. It stays on until a qualified contractor fixes the problem and the repair is reported.
• Don't turn the gas back on or relight the appliance if it was shut off. Leave that to a TSSA-registered gas technician.
• Don't try to repair it yourself. Gas work in Ontario must be done by certified technicians working for a registered contractor.

What to do next

1. Read the notice. Note the category, the problem listed and any deadline.
2. Keep the paperwork. Take a photo of the tag and the notice. Your contractor will need the details.
3. Call a TSSA-registered contractor. Enbridge Gas does not repair or service appliances, so this is up to you. Here's how to check a contractor is registered.
4. Decide: repair or replace. Some problems are a simple fix. Others, like a failed heat exchanger on an older furnace or a leaking water heater tank, usually mean replacement.
5. Close it out. After the work, the contractor sends the required documentation to Enbridge Gas. For a Category B violation, Enbridge says it must visit to verify the repair, and a service charge may apply.

Repair or replace?

If your furnace or water heater is older and the fix is expensive, replacing it is often the better value. It also means the new appliance is installed to current code from the start.

• For furnaces, see furnace replacement cost in the GTA and Southern Ontario.
• For water heaters, see water heater replacement cost in the GTA and Southern Ontario.

Mr. Heating & Home installs Lennox furnaces and tank water heaters across the GTA and Southern Ontario, including Toronto, Mississauga, Oakville, Markham, Durham Region, Kitchener-Waterloo, Guelph and Peterborough. Our installs are done by TSSA-registered, insured and bonded gas technicians. In the GTA, same-day installs are often available when you order early, which matters when the heat or hot water is off, though we can't guarantee it.

Frequently asked questions

Can I still use a red-tagged furnace or water heater?

Not if the gas has been shut off. With a Category B tag, the appliance may stay on for up to 42 days, but only so you have time to arrange the repair. Don't relight or restart anything that's been shut off.

Who can remove a red tag?

Not the homeowner. A TSSA-registered contractor fixes the problem and sends the required paperwork to Enbridge Gas, which may inspect before the matter is closed.

Does Enbridge fix the problem?

No. Enbridge Gas states that it does not repair or service natural gas appliances. You need to hire a TSSA-registered HVAC contractor.

Is there a charge for the follow-up inspection?

For Category B violations, Enbridge says a service charge may apply for the visit to verify repairs.

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Tag categories, the 42-day timeline and follow-up process from Enbridge Gas: Safety violations. Gas-leak steps and emergency number from Enbridge Gas: Smell gas. Checked September 2026. If your gas comes from another utility, follow the instructions on your notice.