nans:
For many years, the model codes, ANSI/ASHRAE Standard 62,
and its predecessor standards have recommended a flat exhaust rate of either 1.5 cfm/ft2 or 6 air changes per hour (ACH) for enclosed parking garages. But because vehicle emissions have been reduced over the years, ASHRAE sponsored a study to determine ventilation
rates required to control contaminant levels in enclosed parking facilities (Krarti and Ayari 1998). The study found that, in some cases, much less ventilation than 1.5 cfm/ft2 was satisfactory. However, local codes may still require 1.5 cfm/ft2 or 6 ACH, so the engineer may be required to request a variation, or waiver, from authorities having jurisdiction before implementing a lesser ventilation
system design. NFPA 88A recommends a minimum of 1.0 cfm/ft2

Imok2

Does ASHRAE standard 62 include formulas etc based on the study by Krarti and Ayari, for multi storey enclosed carparks????

I remember reading the ASHARE guide on thier findings but it was only an example for a single story basement car park however a friend of mine used it as his justification on a variation of the local codes here in Sydeny ( and he succeeded), and it reduced the ventilation requirements by about 30-50% of the Australian Standards.

billyq, I don't have that info, however you may find it here:"Parking Garages", M. Krarti and A. Ayari, Part of Chapter 12 (Enclosed Vehicular Facilities) of ASHRAE Handbook of HVAC Applications, (1999). Hope this helps.