"Return air shall not be taken from a closet, bathroom, toilet room, kitchen, garage, mechanical room, boiler room, furnace room, or unconditioned attic,” according to the 2021 International Residential Code [M1602.2(4)] and the Residential Edition of the Florida Building Code. 

    But there are also six exceptions, and the basis of most of them is that a return air opening is allowed in some forbidden locations as long as the HVAC system only serves that area:
1) Return air opening in a kitchen is allowed as long as the system serves only the kitchen and is located not less than 10-feet away from cooking appliances.
2) Return air opening in a garage is allowed as long as the system serves only the garage. A return air opening in the garage for a system that also serves the living area of a home would be a fire hazard.
3) Dedicated independent dehumidification systems can take air from closets and bathrooms as long as the air is filtered and dehumidified before reintroduced into the spaces.
4) Taking return air from a closet is allowed as long as the return air serves only the closet, and it may be taken from closets that have no dedicated supply duct. There are also several further specs for closets less than 30 square feet.
5) Return air taken from an unconditioned crawl space cannot be done by a direct connection to a forced-air furnace, but a transfer opening in the crawl space enclosure is allowed.
6) Return air from one dwelling cannot be discharged into another dwelling. 

• • • • • • • • • • • • • • • • • • • • • • • • • • • • 

  To learn more about heating and air conditioning systems, see these other blog posts:

• How can I find out the SEER of my air conditioner? 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• Does an old air conditioner use more electricity as it ages? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.