Download all the return air codes from the B149.1-10 Gas Code and 2012 Ontario Building Code below.
The B1491.1-10 Gas Code states,
QuoteClause 4.17.2 - Return air ducts installed in an enclosure shall be in accordance with the provisions set out for duct systems in the National Building Code of Canada.
Clause 7.13.3 - Return-air inlets shall not be installed in an enclosure or crawl space that provides combustion air to a furnace.
The Building Code Section states,
QuoteSection 6.2.3.20(6) - Return-air inlets shall not be installed in an enclosed room or crawl space that provides combustion air to a fuel-fired appliance.
QuoteSection 6.2.4.7(13) - Return-air inlets shall not be installed in an enclosed room or crawl space that provides combustion air to a furnace.
Clause 7.13.3 should be amended to say;
Quote(7.13.3) Return-air inlets shall not be installed in an enclosure or crawl space that provides combustion air to a fuel-fired appliance.