Can HVAC return air be pulled from a bathroom, kitchen, or garage?

No — return air must not be taken from a closet, bathroom, toilet room, kitchen, garage, mechanical room, or a space containing a fuel-burning appliance (IRC M1602.2).

The IRC prohibits a forced-air system from drawing return air from certain spaces. These include closets, bathrooms and toilet rooms, kitchens, garages, mechanical or furnace rooms, and rooms or spaces containing a fuel-burning appliance, among others.

The concern is spreading contaminants, odors, grease, or combustion byproducts, and depressurizing rooms in a way that could backdraft a furnace or water heater.

Pulling return air from these areas can pull flue gases (including carbon monoxide) back into the living space, which is why the prohibition is strict. Return openings must be located in conditioned, occupied areas instead.