Quick answer
Yes, absolutely. In Ontario, anyone working on gas appliances must hold a valid TSSA gas licence (G1 or G2), and your contractor should carry liability insurance and WSIB coverage. Licensed work also means permits get pulled where required. Unlicensed gas work is illegal, voids warranties and insurance, and creates real safety risks — always verify before anyone touches your furnace.
Yes — and in Ontario it isn't a preference. Work on a gas appliance may only be done by a technician holding a valid TSSA gas licence, so before anyone opens your furnace, ask for three things: the technician's licence card, proof of liability insurance and WSIB coverage in the company's name, and confirmation that the permit is included in the price. Those three take five minutes to check and are the difference between a repair your insurer will stand behind and one it can refuse.
The credentials that matter
- TSSA gas licence — the Technical Standards and Safety Authority licenses gas technicians in Ontario. G3 is the entry-level certificate and must work under the supervision of a G2 or G1; G2 covers residential and light commercial appliances; G1 is the unrestricted licence. A house furnace, boiler or gas water heater is G2 work
- Fuels contractor registration — the business itself registers with TSSA, separately from the individual's licence. Ask for both, because a registered company can still send an uncertified helper
- Liability insurance — covers damage to your property if something goes wrong during the work
- WSIB coverage — protects you from liability if a worker is injured on your property. A contractor can produce a clearance certificate on request
- Refrigerant handling (ODP) certification — required for anyone opening an AC or heat-pump refrigerant circuit, and more relevant now that new systems ship on A2L refrigerants
Permits are part of doing it right
Furnace and AC replacements require municipal permits in most GTA cities, and a licensed contractor pulls them as a matter of course rather than asking you to skip them. A permit means an inspector verifies the work is safe — it protects you, not just the city. See do I need a permit to replace a furnace for the specifics.
How to verify before they start
- Ask to see the technician's TSSA card — legitimate techs carry it, and the card shows the name, the licence class and an expiry date worth glancing at
- Confirm the company name on the insurance certificate and the WSIB clearance matches the name on the invoice, not a similar one
- Ask whether they'll pull the permit — the right answer is yes, included, with the number written on the paperwork
- Check that quotes are itemized and in writing, a sign you're dealing with a real licensed business; more in how to choose an HVAC contractor
The real risks of unlicensed work
- Safety — improper gas or venting work can cause gas leaks or carbon-monoxide hazards
- Voided warranties — most manufacturers void equipment warranties if installed by an unlicensed party
- Insurance trouble — your home insurer can deny a claim tied to unpermitted or unlicensed gas work
- No recourse — an uninsured, cash-only operator who botches the job leaves you paying twice to fix it
- A resale problem later — an unpermitted furnace or venting change is exactly what a buyer's home inspection flags, and it gets settled out of your sale price
What licensed work looks like on the invoice
- Equipment model and serial numbers, so the warranty can be registered and looked up years later
- Readings, not adjectives: manifold gas pressure, temperature rise, and a carbon monoxide result after commissioning
- The permit number, and who is booking the inspection
- The technician's name — the same name you saw on the licence card at the door
Questions homeowners ask about licensing
- Can a handyman legally replace my furnace? No. Installing, repairing or disconnecting a gas appliance in Ontario requires a licensed gas technician, no matter how simple the job looks.
- Does a licensed contractor cost more? Not meaningfully. Installation and replacement quotes are free across the GTA, and a repair diagnostic runs $90–$150 whoever you call — the savings on unlicensed work come out of the parts of the job you can't see.
- What about the gas water heater the rental company installed? Rental installers are licensed too. Ask for the same card and the same permit answer you'd ask of anyone else, especially on a chimney-vented tank.
- Is a G3 technician allowed in my house? Yes, working under the supervision of a G2 or G1. The supervising licence-holder is who you should ask about.
- Who do I call if something feels wrong? If you smell gas, leave the house and call Enbridge Gas from outside — see what to do if you smell gas. Concerns about the work itself go to TSSA.
ZK Mechanical's technicians are TSSA-licensed and the company is fully insured and WSIB-covered, and we pull the permits your install requires across the GTA and Hamilton — see why a licensed, insured contractor matters. Request a free quote and we'll show you the credentials before we show you the price.