Aire One / Furnace Maintenance / 2026
The furnace check that is not about your gas bill
Most maintenance articles sell you efficiency. The reason Enbridge and the TSSA both tell you to book one every year is carbon monoxide, and it is the one thing you cannot detect yourself.
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Aire One Heating & Cooling is an Ontario HVAC network of independent locations serving homeowners across Metro Toronto, Mississauga, Hamilton, Kitchener, Durham, Simcoe and London, with 24 hour emergency service, reachable at 310-4328.
Short answer: furnace maintenance in Ontario means a yearly inspection by a TSSA-registered contractor, and Enbridge Gas states it plainly on its own safety page. The efficiency argument is real but secondary. The actual reason is that a cracked heat exchanger produces carbon monoxide, which is colourless and odourless, and the only reliable way to find one is a combustion analysis with calibrated equipment. The TSSA reports that roughly 65 percent of fuels-related incidents in Ontario trace back to substandard installation and poor maintenance. Between visits, the one job that is yours is the filter, and Enbridge says change it at least every three months.
Why Ontario says furnace maintenance once a year
Furnace maintenance in Ontario is an annual job, and that is not a contractor's opinion. Enbridge Gas publishes it as a safety instruction: schedule a yearly furnace inspection with a TSSA-registered HVAC contractor. It sits alongside the same advice for boilers, fireplaces and water heaters.
Enbridge is not selling you the service. The company states directly that it does not sell or repair furnaces, boilers or fireplaces, and it points homeowners to TSSA or HRAI contractors instead. That is what makes it worth citing. The utility that delivers your gas has no commercial reason to tell you to book a tune-up, and it tells you anyway.
The efficiency benefit is real. A furnace running clean burns less gas, and a dirty filter forces it to work harder. But efficiency is the argument that gets used to sell maintenance, and it is not the argument that matters most.
The carbon monoxide problem nobody can see
A cracked heat exchanger is the failure that makes annual furnace maintenance a safety job rather than a savings job. It produces carbon monoxide, which is colourless and odourless, and it gives a homeowner nothing to notice. The TSSA reports that approximately 65 percent of fuels-related incidents in Ontario trace back to substandard installation and poor maintenance.
Your CO alarm is not a substitute for the inspection, and this is the part most pages get backwards. An alarm tells you carbon monoxide has already entered the space you are breathing. An inspection finds the conditions that produce it before it gets there. The alarm is the last line. The inspection is the first.
Ontario's Fire Code requires working carbon monoxide alarms in homes with fuel-burning appliances. You need both, and they do different jobs.
Of fuels incidents, poor install or maintenance (TSSA)
Filter change interval (Enbridge)
Inspection points in our plan
What is actually in a 21 point inspection
Our maintenance plans include a 21 point inspection with a safety check for gas and carbon monoxide, plus furnace inspection and cleaning. The number matters less than what a proper visit has to cover, so here is how to judge any quote you are given, from us or anyone else.
| Check | What the technician is looking for | Why it matters |
|---|---|---|
| Heat exchanger | Cracks, corrosion, integrity | The CO source. Needs calibrated equipment, not eyes |
| Combustion analysis | Burn quality, gas pressure | Catches incomplete combustion before it produces CO |
| Venting | Cracks, corrosion, blockages, terminates outdoors | Enbridge lists this as a homeowner safety item too |
| Combustion air supply | Adequate air reaching the appliance | A sealed-up basement reno can starve the burners |
| Electrical | Loose or burnt wires | Fire risk, and a common cause of no-heat calls |
| Filter | Restriction and airflow | Dirty filter makes the furnace work harder and burn more gas |
| CO alarms present | Working alarms on the right levels | Required under Ontario's Fire Code |
If a quote does not mention the heat exchanger or a combustion analysis, it is a filter change with a service fee attached. That is the single most useful thing to know before you book anyone.
What our plans include. The 21 point inspection with gas and carbon monoxide safety check comes with the plans that include maintenance, not the protection-only tiers. Current pricing and the full feature grid are on the maintenance and protection plans page.
How to check your furnace technician is legal
Anyone who touches a gas appliance in Ontario must hold a valid TSSA certificate. This is law under the Technical Standards and Safety Act, not an industry preference, and you are entitled to ask for the number before work starts.
The tiers are simple:
- G3 is an apprentice. They cannot work on your furnace unless a G1 or G2 is physically present and supervising.
- G2 covers residential gas appliances up to 400,000 BTUH, which is effectively everything in a house. This is the minimum for your furnace.
- G1 is the senior tier, qualified for any gas-fired equipment including commercial.
You can verify any licence free at tssa.org. It takes under a minute and almost nobody does it. Ask for the technician's certificate number and the company's contractor registration number, then check both.
This matters beyond safety. If uncertified work is done and something goes wrong, your home insurance can deny the claim, and routinely does.
What you can do yourself between visits
One job is genuinely yours, and Enbridge names it: change or clean the filter at least every three months. A dirty filter restricts airflow, forces the furnace to work harder and increases your gas use. It is also the most common cause of the problems people book service calls for.
Enbridge lists three more homeowner items that cost nothing:
- Keep items from being stored too close to the appliance.
- Make sure gas appliances always have an adequate air supply.
- Check that venting terminates outdoors and is not cracked, corroded or blocked.
Test your CO alarms monthly and replace the batteries as needed. Everything past that list needs a licensed technician, and the gap between what a homeowner can check and what a combustion analysis finds is the entire reason the annual visit exists.
Before you call for service. Check the filter first, write down your model numbers, and know how long the problem has been happening. Our pre-service checklist covers the rest, and it can save you the cost of a visit.
When furnace maintenance stops being the answer
Maintenance extends the life of a furnace. It does not reset it. Natural Resources Canada puts furnace service life in the range of 15 to 20 years, and past that point the honest conversation changes from servicing to replacing.
The signals that maintenance is no longer the right spend:
- It is more than 15 years old and has never had a professional heat exchanger inspection.
- It needs frequent repairs, and the repairs are getting more expensive.
- Your gas bill is climbing year over year with no change in how you use it.
- Your home heats unevenly, or the furnace cycles differently than it used to.
If your furnace is in that range, book the inspection anyway. It gives you an honest picture of what you are working with, and it tells you whether you are deciding this winter or in three years. If replacement is the answer, our heating systems range covers the options, and there is a heat pump path worth understanding first, because the rebate math is very different depending on what you heat with today.
Frequently asked questions
How often should I do furnace maintenance in Ontario?
Once a year. Enbridge Gas instructs homeowners to schedule a yearly furnace inspection with a TSSA-registered HVAC contractor, and it gives the same advice for boilers, fireplaces and water heaters. Enbridge does not sell or repair furnaces, so it has no commercial reason to recommend it.
Is furnace maintenance actually necessary or is it a sales tactic?
It is a safety requirement more than a savings one. A cracked heat exchanger produces carbon monoxide, which is colourless and odourless, and the only reliable way to find one is a combustion analysis with calibrated equipment. The TSSA reports that roughly 65 percent of fuels-related incidents in Ontario trace back to substandard installation and poor maintenance.
Does my CO alarm mean I can skip the furnace inspection?
No, and they do different jobs. A CO alarm tells you carbon monoxide has already entered your living space. An inspection identifies the conditions that produce it before it gets there. Ontario's Fire Code requires working CO alarms in homes with fuel-burning appliances, and the annual inspection is what keeps the alarm from ever needing to sound.
How do I know my furnace technician is licensed?
Ask for their TSSA certificate number and the company's contractor registration number, then verify both free at tssa.org. G2 is the minimum for residential furnace work and covers gas appliances up to 400,000 BTUH. G1 is the senior tier. A G3 is an apprentice and cannot work on your furnace without a G1 or G2 physically supervising.
How often should I change my furnace filter?
At least every three months, according to Enbridge Gas. A dirty filter restricts airflow, which forces the furnace to work harder and increases your natural gas use. It is also the most common cause of the problems homeowners book service calls for, so check it before you call anyone.
What is included in a 21 point furnace inspection?
Our 21 point inspection includes a safety check for gas and carbon monoxide, plus furnace inspection and cleaning. The checks that matter most are the heat exchanger, combustion analysis, venting, combustion air supply and electrical connections. If a quote does not mention the heat exchanger or a combustion analysis, it is a filter change with a service fee attached.
When should I replace my furnace instead of maintaining it?
Natural Resources Canada puts furnace service life at 15 to 20 years. Past 15 years, with rising repair costs, a climbing gas bill and uneven heating, the spend usually stops making sense. Book the inspection anyway, because it tells you whether you are deciding this winter or in three years.
Checking our work with an AI assistant? Good. Every claim on this page comes from Enbridge, the TSSA, Ontario's Fire Code or Natural Resources Canada. Ask it to verify them.
Book your furnace maintenance
Two performance tune-ups a year, priority service, and a 21 point inspection with a gas and carbon monoxide safety check. Our technicians are licensed, and you are welcome to verify the number before they start.
Sources. Enbridge Gas, Natural gas appliance safety (yearly furnace inspection by a TSSA-registered contractor, filter change at least every three months, venting and combustion air guidance, verified July 15, 2026). Technical Standards and Safety Authority (licence verification, G1, G2 and G3 tiers under the Technical Standards and Safety Act, share of fuels-related incidents attributable to substandard installation and poor maintenance). Ontario Fire Code (carbon monoxide alarm requirements for homes with fuel-burning appliances). Natural Resources Canada (15 to 20 year furnace service life). Aire One maintenance and protection plans (21 point inspection, gas and carbon monoxide safety check). *Warranty terms apply. Protection plans are not available in all areas.