Overview
This bulletin is being issued for safety purposes as it relates to an incident involving the failure of a venting system and subsequent carbon monoxide poisoning. The following refers to gas
installations utilizing Category III (positive pressure non-condensing) venting systems installed horizontally. This is commonly known to industry as sidewall vented stainless steel.
TSASK Gas Inspections is reminding all gas contractors that with the installation of category III appliances such as boilers, or unit heaters popular for storage garage heaters, that the installation
of the Category III venting systems must be in accordance with the installation instructions provided by the venting system manufacturer as directed by CSA B149.1-20 clause 8.10.4.
In Canada, Category III venting systems are certified to ULC-S636. Typically, the instructions for the horizontal installation of a Category III venting system require a continuous slope upwards as
it moves away from the appliance.
Depending upon their application, some venting systems will require that a drain fitting be installed in the venting system in accordance with the vent and/or appliance manufacturer’s
instructions.
Category III venting systems installed contrary to their installation instructions, such as horizontally sloped down and away from the appliance, will not be permitted.
If you have any questions or concerns, please contact your local inspector.