In short
The TSSA, or Technical Standards and Safety Authority, is Ontario's public-safety regulator for fuels, boilers and pressure vessels, elevators and amusement rides. For a homeowner it means two things to check before gas work starts: the company's TSSA fuels contractor registration and the technician's own G1, G2 or G3 gas certificate. One without the other is not enough.
Every gas furnace, boiler, water heater, fireplace and gas line in Ontario falls under rules the TSSA enforces. The authority sells nothing and does not work for contractors; it administers the Technical Standards and Safety Act, 2000 and the fuel regulations made under it on the province's behalf. The installation rulebook those regulations adopt for natural gas and propane is the CSA B149.1 code.
What the TSSA regulates on a home gas job
Two separate credentials apply to a furnace, boiler, water heater or gas line job, one held by the company and one by the person doing the work.
- Contractor registration: the business must be registered with the TSSA as a fuels contractor before it offers to install, service or remove a gas appliance
- G3 certificate: the entry level, held by a technician who installs and repairs under the supervision of a G2 or G1
- G2 certificate: a technician who may work alone on appliances rated up to 400,000 BTU per hour, which takes in the furnaces, boilers and water heaters found in houses
- G1 certificate: no input limit, the class needed for large commercial and industrial equipment
What the TSSA does not do
The TSSA does not inspect every residential installation. A furnace or water heater replacement is the responsibility of the registered contractor and the certified technician who did it, and TSSA inspectors audit contractors and investigate incidents and complaints instead of visiting each house.
It also does not set prices, referee billing disputes or cover refrigerant and electrical work. Refrigerant handling needs an ODP card, wiring falls under the Electrical Safety Authority, and building permits come from your municipal building department. A disagreement over an invoice is a consumer-protection matter, not a TSSA one.
Where the TSSA does reach into a house is the warning tag. A gas technician who finds an unsafe appliance is required to tag it and, when the hazard is immediate, shut off its gas; our answer on what a red tag on a furnace means covers what happens next.
What to ask for before gas work starts
Ask for the paperwork before the job, not after.
- The TSSA contractor registration number, written on the quote
- The technician's certificate card on site, showing the class (G1, G2 or G3) and an expiry date that has not passed
- Proof of liability insurance and WSIB coverage, which are separate from any TSSA document
- A written scope naming the appliance, the venting and the gas piping being touched
The step-by-step lookup is in our guide on how to verify a TSSA licence, and the wider checklist is in should my HVAC technician be licensed and insured. If you believe gas work in your home was done unsafely, or by someone working for pay without a certificate, you can report it to the TSSA directly. If you smell gas, leave the house first and call Enbridge Gas or 911 from outside.
What hiring an unregistered installer costs you
An uncertified installer leaves you holding the risk. Manufacturers can refuse warranty on equipment that was not installed by a certified technician, an insurer can question a claim that traces back to the work, and the next licensed technician who finds a hazard has to tag it. Correcting someone else's venting or gas piping is billed on top of the original job.
ZK Mechanical is owner-operated by a TSSA-licensed gas technician, and a high-efficiency furnace installation runs $4,500–$7,500 with the price fixed in writing before work starts. Ask for the registration number and the certificate card when we quote; we expect the question. Other paperwork terms are in the HVAC glossary, and quotes are free through our contact page.
Questions people ask about TSSA
Does the TSSA inspect my new furnace after it is installed?
Not as a routine step. The registered contractor and the certified technician are responsible for an installation that meets the gas code, and the TSSA audits contractors and investigates incidents and complaints. A building permit, where your municipality requires one, is a separate process with its own inspection. Keep the invoice, the contractor's registration number and the technician's name with your furnace paperwork.
What is the difference between a G1, G2 and G3 gas licence?
They are certificate classes for individual gas technicians. A G3 is the entry level and works under supervision. A G2 may work independently on appliances rated up to 400,000 BTU per hour, which takes in residential furnaces, boilers, water heaters, fireplaces and their gas piping. A G1 has no input limit and handles large commercial and industrial equipment. In a house, a G2 or G1 should be the one responsible for the job.
Is TSSA registration the same as a business licence or insurance?
No. TSSA registration says only that the company is permitted to do fuel work in Ontario. It is not a municipal business licence, liability insurance, WSIB coverage or a refrigerant ODP card, and it says nothing about price or workmanship warranty. A contractor replacing a furnace and an air conditioner together needs gas credentials for the furnace and an ODP-certified technician for the refrigerant side.