Quick answer
Yes. Get a second opinion on a red-tagged furnace whenever the fix quoted is a new furnace or a major repair and you were not shown proof. Any TSSA-licensed gas technician can assess it, but the furnace stays off and the tag stays in force until the defect is corrected or shown not to exist and Enbridge Gas is notified. Ask for the combustion printout and photos first.
You should get a second opinion on a red-tagged furnace in one situation above all: the technician who tagged it is also the one selling the replacement, and the evidence stayed in their toolbox. A red tag is a legal safety notice, and most are written honestly. It is also the strongest sales lever in the trade, which is why checking it is your right and costs little next to the price of a furnace.
You are entitled to a second TSSA-licensed assessment, but the tag stays on
Nothing in Ontario's gas rules ties you to the company that wrote the tag. You can call any TSSA-registered heating contractor and have a licensed gas technician inspect the same furnace. What you cannot do is turn the gas back on, remove the tag yourself or run the furnace while you wait.
The tag stays in force until a licensed technician either corrects the defect or documents that it does not exist, and the gas distributor, Enbridge Gas across this area, is notified. A second technician who disagrees with the first does not simply pull the tag off: they inspect, record their readings and put their own certificate number on the result. The tag types and their deadlines are explained in what a red tag means in Ontario.
The evidence to ask for before you agree to anything
A real defect leaves a record. Ask the first technician for these, and hand them to the second:
- The combustion-analysis printout, or a photo of the analyzer screen: oxygen, carbon monoxide in the flue gas and stack temperature, with the date and time.
- Ambient carbon monoxide readings, in parts per million, taken in the furnace room and at a supply register while the furnace was running.
- A photo or video of the crack, hole or corrosion, taken with an inspection camera and showing where on the heat exchanger it sits.
- The tag itself, filled in: the specific defect, the technician's name and gas certificate number, the date and the contractor's name.
- The furnace model and serial number, so the age and any heat-exchanger warranty can be checked.
A technician who found a genuine crack is usually glad to show it, because the record protects them too. "I can tell by the flame" or "it is old, so it is cracked" is an opinion, not a finding. If no printout and no picture exist, that alone is reason enough for a second visit.
Pressure-sale red flags, and Ontario's ban on door-to-door furnace sales
Be suspicious of a tag when the visit arrived uninvited or the sales pitch arrived before the evidence. Ontario bans unsolicited door-to-door sales of furnaces, air conditioners, water heaters and duct cleaning. A contract signed as a result of that kind of visit is void, and a contract signed in your home carries a 10-day cooling-off period that starts when you receive the written copy.
- A "free inspection" or "mandatory safety check" you did not book, often from someone implying they represent the utility or the government. Neither Enbridge Gas nor the TSSA sells furnaces at the door.
- A replacement quote, often a long rental contract, produced on the spot with a price that expires tonight.
- No printout, no photo, and a refusal to let you see the defect for yourself.
- A tag with no certificate number, or with "unsafe" written where the specific defect should be.
- Pressure to sign before another company can look, or a claim that a second opinion is "not allowed".
The common scripts, and how to cancel a contract signed under them, are set out in how to spot an HVAC scam in Ontario.
What a second opinion involves and what it costs
A second opinion is a full diagnostic, not a glance. The technician reads the tag, inspects the heat exchanger with a camera, checks the venting and the safety controls, runs a combustion analysis if the furnace can be fired safely while they stand at it, measures carbon monoxide in the room air and writes the result down.
- Service call and diagnosis: $90–$150, taken off the bill when you approve the fix.
- Repairs that commonly clear a tag, such as a failed pressure switch, a blocked vent, a flame sensor or an inducer motor: most fall between $150 and $800.
- Heat exchanger replacement: $1,500–$3,000 in parts and labour, money that on a furnace over 15 years old is usually better put toward a new one.
- New high-efficiency furnace, if the second inspection confirms the furnace is finished: $4,500–$7,500 installed, quoted in writing.
The decision rule is simple. If the second technician confirms the defect with the same kind of evidence, the tag was right and the only question left is repair or replace. If they cannot find it, you get that in writing, the condition is cleared through the proper channel and the furnace goes back into service.
Staying warm and safe while the furnace is tagged
Leave the furnace off until the second inspection is done. A tag for a cracked heat exchanger, a spilling vent or a failed safety control exists because the furnace can put carbon monoxide into the house. Use electric space heaters on separate circuits, keep them clear of bedding and curtains, open the cabinet doors under sinks on outside walls and confirm your CO alarms are working. Never use the oven or a barbecue for heat.
ZK Mechanical carries out furnace second opinions across Burlington, Oakville, Hamilton, Milton and Mississauga, and the readings and photos stay with you whichever way the result goes. If the tag is confirmed, furnace repair or a written replacement quote follows. Call (647) 801-1252 or book the inspection through the contact page, and have the tag in hand when you do.