TSSA safety checks for applicable residential natural-draft boilers
The heating-season requirement applies to a defined class of boilers—not every boiler in Ontario.
The TSSA check applies to specified residential natural-gas or propane natural-draft boilers with a draft-control device and an input of 300,000 BTU/h or less. When a gas technician attends for service, maintenance or emergency work, the check is required once per heating season unless a valid tag confirms it was already completed.
If a CO alarm sounds, you smell gas, see smoke or believe there is an immediate danger, get everyone outside and call 911 from outside.
Why the equipment description matters
Natural draft describes how combustion products move through the venting system. A boiler with different venting, input or application may fall outside this particular requirement while still needing appropriate maintenance and safety assessment.
Do not decide applicability from the boiler’s age or appearance alone. The rating plate, venting and draft-control arrangement need to be identified.
What the prescribed check includes
The TSSA requirement includes a visual inspection and a flue-gas carbon-monoxide reading for the applicable boiler. The technician documents the result and uses the prescribed process when unsafe conditions or excessive readings are found.
Once per heating season
If the check has already been completed for that heating season, a valid inspection tag provides the record. Without that confirmation, an attending gas technician may need to perform the required check even when the original call was for another service issue.
If you are unsure
Tell the shop you have a boiler when booking and, if possible, provide a clear photo of the unit and rating plate. A licensed gas technician can determine whether the rule applies. Required testing can be additional to an ordinary clean-and-service appointment.