Directive: Appliance air intake clearance to pressure relief device vent outlet
October 1, 2022
This Directive is being issued by a Provincial Safety Manager pursuant to section 30 of the Safety Standards Act.
There are instances with-in the CSA B149.1 Natural gas and propane installation code where further clarity is required regarding minimum clearances. This directive defines the minimum clearance requirement for appliance air supply inlets (combustion air) in order to resolve installation related conflicts in British Columbia.
An appliance air intake is not defined in the CSA B149.1, therefore in British Columbia it shall be categorized in two ways, either as passive (natural draft combustion air intake) or fan/blower assisted (mechanically draws air in for combustion).
Technical Safety BC interprets the appliance air intake referenced in Table 5.3 to be as passive based on past use of the term in relation to Category I or II appliances. Combustion air for Category III or IV appliances installed as direct vent 2 pipe installations shall be considered as fan/blower assisted. Fan/blower assisted appliance air inlets for both Natural Gas and Propane installations are to be terminated no less than 10 ft (3 m) in any direction in accordance with the clearances for mechanical air intakes in Table 5.3 from a regulator relief or over pressure line relief device outlet where gas may be vented to atmosphere.
Clearances from the discharge of a certified overpressure protection device that conforms to ANSI Z21.80/CSA 6.22 are listed in the first column in Table 5.3. Passive air intakes must have a clearance of 1 ft (0.3 m). Fan/blower assisted air intakes must have a clearance of 3 ft (1 m).
Provincial Safety Manager, Gas
Safety Standards Act
Gas Safety Regulation
CSA B149.1 - Natural gas and propane installation code