Ontario · Energy · checked September 28, 2026

Combustion safety testing in Markham

A combustion safety test checks that your furnace, water heater and fireplace vent their exhaust outside instead of into the house, which matters most right before and after you tighten the house up. In the Toronto area, the main heating energy is natural gas for 52% of households.

Get matched in Markham → The combustion safety and spillage check
A gloved hand inserting a combustion analyzer probe into a furnace flue pipe in a basement

Cost

Included with an evaluation

Natural gas heat

52%

Gas distributor

Enbridge Gas

CO alarms required (existing homes)

Yes

How Markham is built

Markham's houses by when they were built Ten house shapes, one for each tenth of Markham's 91,305 houses. Before 1961: 3%, 1961–1990: 38%, 1991–2000: 17%, 2001 or later: 43%. Older houses glow hotter.
  • Before 1961 3%
  • 1961–1990 38%
  • 1991–2000 17%
  • 2001 or later 43%
Each house stands for one in ten of Markham's 91,305 houses (single-detached, semi-detached, row and duplex), drawn by when it was built. The glow shows the usual pattern: older houses tend to be leakier and less insulated. Snowfall scales with heating degree-days. Sources: Statistics Canada 2021 Census (table 98-10-0233-01), NRCan HOT2000 climate data.

Why it matters in Markham

In the Toronto area, 59% of households heat mainly with a forced-air furnace, 8% with a boiler and radiators, 5% with electric baseboards and 4% with a heat pump; natural gas is the main heating energy for 52% of households and electricity for 18% (Statistics Canada, 2023).

The risk rises after air sealing: a tighter house plus a strong exhaust fan or dryer can pull exhaust back down a chimney. That's why advisors test for spillage during an evaluation and why it should be repeated after serious tightening.

The CO alarm rule in Ontario

Ontario's Fire Code requires CO alarms in existing homes that have a fuel-burning appliance, a fireplace or an attached garage: next to every sleeping area and, since January 1, 2026, on every storey as well.

What the check involves

  • Worst-case depressurization: exhaust fans and the dryer on, doors set to make the appliance room as negative as it gets.
  • A spillage and draft check at each appliance, with a CO reading.
  • A plan if anything fails: often a sealed-combustion appliance or a fix to the venting, done by a licensed gas or oil technician.

The combustion safety check in detail.

NRCan-licensed service organizations serving Markham

Energy advisors check for combustion spillage during an evaluation; fixing a venting problem is work for a licensed gas or oil technician.

Only assessments from the seven HRSP-approved organizations qualify for the $600 Home Renovation Savings rebate and its assessment-path upgrade rebates; each listing below says whether it's one of them.

Source: NRCan list of licensed service organizations, checked September 28, 2026. Call to confirm your street is covered and ask about wait times.

Programs in Markham

Provincial · needs an evaluation Home Renovation Savings — Home Energy Assessment path Up to $10,000 per home for insulation, windows and air sealing, plus $600 back on your assessments — if the follow-up assessment is done by December 31, 2026 Open · deadline

Combustion safety test in Markham: common questions

Are CO alarms required in Markham homes?

Ontario's Fire Code requires CO alarms in existing homes that have a fuel-burning appliance, a fireplace or an attached garage: next to every sleeping area and, since January 1, 2026, on every storey as well.

Who does combustion safety testing?

Energy advisors check for spillage during an EnerGuide evaluation. Repairs to venting or appliances are done by a licensed gas or oil technician.

I have CO alarms. Isn't that enough?

Alarms warn you once CO is already in the house. A spillage test finds a venting problem before it produces CO.

Combustion safety test near Markham

Combustion safety test in Richmond Hill10 kmCombustion safety test in Pickering15 kmCombustion safety test in Vaughan18 kmCombustion safety test in Toronto19 kmCombustion safety test in Ajax22 km All 70 cities →

Sources

Checked September 28, 2026. Census figures are for the municipality (Ontario); climate data is NRCan's HOT2000 station Toronto Buttonville (6 km away).

Get matched with a registered advisor in Markham

Tell us your postal code and what you’re planning. We’ll connect you with one licensed service organization serving your area. No spam, no shared lead lists.

Email us what you’re planning, your postal code and the type of building (a house, a duplex or triplex, or a larger multi-unit building) — we’ll reply with registered service organizations for your area and which rebates apply.

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