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What We Think We Know About Ventilation



Andrew K. Persily


The amount of outdoor air provided to occupied spaces is one of the most important determinants of indoor air quality, but many critical questions and misunderstandings still exist regarding outdoor air ventilation. First, given the importance of ventilation, how well do we know how much outdoor air is even needed in buildings? While research has been done on ventilation and odor perception and on ventilation and symptom prevalence, is it adequate to support the ventilation requirements in our standards and regulations? While this research and many years of designing and operating buildings have been used to develop ventilation requirements in standards and regulations, these requirements treat all buildings the same. Can we provide understandable and practical ventilation requirements that address the tremendous variability in buildings and occupants? While much time and effort is spent developing and debating ventilation requirements, compliance with these requirements in design and ultimately operation is rarely given the attention that it deserves. Determination and control of actual ventilation performance in buildings requires measurement, which is extremely difficult to conduct in the field and is too often omitted from building management practice, as well as indoor air quality research. Ventilation measurements often reveal significant gaps between design intent and actual performance with serious implications for both indoor air quality and energy. Given the importance of ventilation, the research that has been done and the many questions that remain, it is reasonable to ponder how much we really know about ventilation.
Proceedings Title
Indoor Air 2005
Conference Dates
September 4-9, 2005
Conference Location
Bejing, CN
Conference Title
The 10th International Conference on IAQ and climate


airflow, building codes, indoor air quality, measurement, regulation standards, ventilation


Persily, A. (2005), What We Think We Know About Ventilation, Indoor Air 2005, Bejing, CN, [online], (Accessed May 23, 2024)


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Created September 1, 2005, Updated February 19, 2017