ASHRAE Standard 62-1999, Ventilation for Acceptable Indoor Air Quality, contains requirements for minimum ventilation rates in buildings. As this standard is being revised, proposals are being discussed to modify these ventilation rates. In reviewing the current rates and proposals to revise them, it is important to understand the scientific research behind these rates and the engineering experience that supports them. Among the relevant research are numerous studies conducted in both chambers and in occupied buildings in which body odor perception was measured as a function of ventilation rate. These studies have shown consistently that 80% of adapted occupants are satisfied in terms of their perception of human body odor at ventilation rates of 2.5 L/s (5 cfm) per person. In addition, about 80% of unadapted visitors are satisfied at 7.5 L/s (15 cfin) per person. Of course, there are other indoor pollutants that impact perception and health besides the bioeffluents associated with body odor. In establishing ventilation rate requirements, a number of key decisions must be made including whether the requirements are established based on adapted occupants or visitors and how non-occupant related pollutants are factored into the required rates.