A ventilation standard debate : Should pollutant source strengths be added when calculating ventilation rates ?

Fundamental to the design of residential and commercial buildings is the calculation of appropriate levels of ventilation. Since 1989, ANSI/ASHRAE Standard 62-1989, Ventilation for Acceptable Indoor Air Quality, has provided guidelines for design engineers in specifying adequate ventilation. Standard 62-1989 and other international ventilation standards incorporate the Maximum Source Principle, which states that diluting the strongest pollution source in a room will naturally provide enough ventilation to dilute other pollution sources present as well. However, a recently proposed change to Standard 62-1989 would forgo the Maximum Source Principle in favor of the Additivity Principle, which states that each pollution source in a room requires its own dilution ventilation, and thus the strengths of all pollution sources, no matter how different, should be added together and ventilation provided for this total source. The use of the Additivity Principle, which we will show is unsupported, represents a radical departure from the established utility of the Maximum Source Principle. This would result in standards that require dramatically increased amounts of ventilation relative to current standards. However, the Additivity Principle has been the subject of much debate within the engineering community. In the remainder of this article we examine the background of evidence for and problems with the use of the Additivity Principle in setting ventilation standards.