Building Ventilation Background

This section of the web site reviews what is known about the influence of building ventilation rates on occupant health and performance. As indicated in the following list, many features of buildings, outdoor environmental conditions, and occupants will affect whether and how ventilation rates influence health and performance:

• If a building has strong indoor sources of air pollutants, increased ventilation will more strongly reduce indoor concentrations of these pollutants, increasing the potential for health benefits.
• If the outdoor air is highly polluted, increased ventilation may increase indoor concentrations of outdoor air pollutants, diminishing the health benefits of increased ventilation or making increased ventilation harmful to health.
• If the outdoor air supplied by a building ventilation system passes through an efficient particle filter, increased ventilation will only slightly increase indoor concentrations of outdoor air particles, reducing the potential adverse health effects of outdoor air particles.
• If the outdoor air is highly humid, increases in ventilation may increase indoor humidity sufficiently to increase indoor levels of house dust mites or molds, posing health risks.
• If the outdoor air is cool and dry, increased ventilation may help to maintain indoor humidity below the levels that support survival of house dust mites, potentially reducing mite-related allergies and asthma.
• The influence of ventilation rates on health may depend on the susceptibility of occupants to pollutant-caused health effects. Occupant age, and preexisting health conditions, such as allergies, asthma, and cardiovascular diseases, may affect whether and how much ventilation rates influence occupant health.

Given the many influencing factors, we must expect a range of findings among studies of the relationship of ventilation rates with occupant health and performance. By pooling the results of multiple studies, we can gain an understanding of the typical or most common effects of changing ventilation rates, while maintaining an awareness of the expected variability.