Air Conditioning Supply AIr

[mtCDCcb]

We have an R-2 building that has an air conditioning system that was retrofitted about 10 years ago. They pull the supply air from the enclosed parking garage on the bottom level. Is this allowed by the IBC/IMC?

[Jerry Peck - Codeman]

As I am reading the question, you are asking about fresh air intake (ventilation air) which is drawn into the building,

If so, I would start with IMC 404 Enclosed Parking Garages, 404.2, which requires the occupied structures accessory to the garage to be maintained at a positive pressure relative to the garage, and shall be provided with ventilation per 403.3.1, where 403 is Outdoor air and local exhaust airflow rates ... with the key being "outdoor air" ... and a parking garage, enclosed or open, is not "outdoor air".

Going back to 404.2, the intent is that the occupied structure accessory to the parking garage are maintained at a positive pressure to the parking garage so air from the parking garage is not drawn into the other occupied spaces.

To intentionally draw air from the parking garage into the other occupied areas of the structure defeats the purpose of maintaining of positive pressure in the other occupied areas of the structure accessory to the parking garage.

The term "Occupied spaces accessory to parking garages." may be what brings confusion as the parking garage is more accessory to the rest of the structure than the rest of the structure is accessory to the parking garage, however, the code states, in 404.2, "connecting offices, waiting rooms, ticket booths, and similar uses that are accessory to a parking garage ... " would also include elevators and elevator lobbies, stairways and their lobbies, and the building areas to which those lead.

Keep the parking garage air out of the other occupied areas, even areas as small as "ticket booths" (which are occupied) need to be maintained at a positive pressure to the parking garage.