An existing open parking garage undergoing renovations fell just short of the required free area to not require mechanical exhaust, based on current prescriptive code requirements.
The historic structure proved difficult to meet the prescriptiveness of the code; any additional modifications would be proven to be difficult to achieve and costly.
Computational fluid dynamics (CFD) through Fire Dynamics Simulator (FDS) examined a conservative amount of vehicles operating simultaneously within the parking garage. The results indicated that the currently proposed arrangement and free area of opening provided equivalent results to that of which of the prescriptive solution (i.e. slightly more free area on the exterior perimeter).
The results of this modeling effort resulted in additional openings in the exterior boundary being required; additional locations were limited to tenant spaces, and thus loss of leasable space and cost implications would had been significant.
International Building Code (IBC) Section 406.5, Open Parking Garages
International Mechanical Code (IMC) Parking Garage Ventilation
Fire Dynamics Simulator (FDS)