The 2026 B-Vent Rule: Why More Furnaces and Water Heaters Are Getting Tagged for Venting

What did the 2026 amendment change?

The amendment addresses Type B vent — the double-wall metal vent used on atmospherically vented and mid-efficiency gas appliances — where the installation does not comply with current requirements. Under the amendment, non-compliant Type B venting must be replaced with a code-compliant venting system in accordance with Ontario Regulation 212/01 unless a defined set of conditions is met.

It does not change what a red tag is or how one is cleared. What it changes is how often an inspecting technician has to write one on a venting arrangement that had been passing for years.

The specific conditions that allow existing venting to remain are set out in the amendment itself, and they should be read from the source document rather than paraphrased:

[INSERT VERIFIED CONDITION LIST FROM TSSA FS-279-26]

Red Tag Relief is not affiliated with the TSSA and does not speak for it. Confirm the current text of FS-279-26 directly from the TSSA before relying on any summary of it, including this one.

Is a B-vent tag an immediate shut-off?

Generally no. Non-compliant venting under this amendment sits in the 90-day correction category, which means a Type B tag: the appliance can usually continue to operate while you arrange the correction, and you have a deadline printed on the tag.

That changes if the technician finds an active hazard alongside the venting non-compliance — spillage into the living space, a disconnected vent, elevated carbon monoxide, a failed heat exchanger. Any of those is an immediate hazard on its own and produces a Type A tag with the gas locked.

The deadline printed on your tag governs. If it says something other than 90 days, follow the tag.

Who does this affect most?

Older homes venting into a masonry chimney. Where a mid-efficiency furnace or an atmospheric water heater vents into a clay-lined or unlined masonry chimney, the connector and liner arrangement is exactly what this amendment is aimed at.

Shared venting is the second group. A furnace and a water heater common-vented into one flue is a sizing calculation, and many of these installations were done when the connected appliances were different from what is there now — typically after a furnace was upgraded and the water heater was left orphaned in a flue far too large for it.

Mid-efficiency appliances generally. High-efficiency condensing equipment vents in plastic through a sidewall and is outside this scope. If your furnace is 80% efficient with a metal vent to a chimney, you are in the affected population.

What does the fix usually involve?

In most cases it is a venting correction, not an appliance replacement. Typical work is installing a correctly sized listed liner in the chimney, replacing or re-pitching the vent connector, correcting connector length, rise and clearances, or re-arranging a common vent so the connected appliances are properly sized to it.

Where the chimney itself has failed — spalled liner, blockage, water damage, structural movement — the correction moves into masonry or chimney specialist scope, and it is coordinated rather than handed back to you.

The correction is verified the same way any venting tag is cleared: draft and spillage testing under worst-case conditions, combustion analysis, and a written correction record.

Does a venting tag mean I need a new furnace?

No. A venting tag is about how flue products leave the building, not about whether the appliance works. A perfectly serviceable furnace can be tagged for a vent it shares with something else.

There are two situations where replacement genuinely enters the conversation. One is where the appliance itself has a separate defect, such as a cracked heat exchanger. The other is where the cost of correcting the venting on an old mid-efficiency appliance approaches the cost of moving to a condensing appliance that vents through the wall and removes the chimney problem entirely.

That is a decision with numbers attached, and you should be given both numbers. If someone quotes you a furnace off a venting tag without showing you the venting correction price, get a second opinion.