Outside or return air for a heating or cooling air systems shall not be taken from the following locations:
- less than 10 feet (3048 mm) in distance from an appliance vent outlet, a vent opening of a plumbing drainage system, or the discharge outlet of an exhaust fan or a medical-surgical vacuum outlet, unless the outlet is 3 feet (914 mm) above the outside-air inlet.
- Less than 10 feet (3048 mm) above the surface of an abutting public way, sidewalk, street, alley, or driveway.
- A hazardous or insanitary location, or a refrigeration machinery room as defined in this code.
- An area, the volume of which is less than 25 percent of
the entire volume served by such system, unless there is
a permanent opening to an area the volume of which is
equal to 25 percent of the entire volume served.
Exception: Such openings where used for a heating or cooling air system in a dwelling unit shall be permitted to be reduced to not less than 50 percent of the required area, provided the balance of the required return air is taken from a room or hall having not less than three doors leading to other rooms served by the furnace. - A closet, bathroom, toilet room, or kitchen.
- Rooms or spaces containing a fuel-burning appliance
therein. Where such room or space serves as source of
return-air.
Exceptions:
- This shall not apply to fireplaces, fireplace appliances, residential cooking appliances, direct-vent appliances, enclosed furnaces, and domestic-type clothes dryers installed within the room or space.
- This shall not apply to a gravity-type or listed vented wall heating or cooling air system.
- This shall not apply to a blower-type heating or
cooling air system installed in accordance with the
following requirements:
- Where the return air is taken from a room or space having a volume exceeding 1 cubic foot (0.03 m3) for each 10 Btu/h (0.003 kW) fuel input rating of fuel-burning appliances therein.
- Not less than 75 percent of the supply air is discharged back into the same room or space.
- Return-air inlets shall not be located within 10 feet (3048 mm) from an appliance firebox or draft diverter in the same enclosed room or confined space.