Summary

Ventilation, as defined here, is the supply of outdoor air to a building. Ventilation rates vary considerably from building to building and over time within individual buildings. Throughout the normal range of ventilation rates encountered in buildings, increased ventilation rates are, on average, associated, with fewer adverse health effects and with superior work and school performance. There is also some limited evidence that occupants of buildings with higher ventilation rates have lower rates of absence from work or school. The main findings of related scientific research are as follows:

Ventilation Rates and Office Work Performance: Performance (speed and accuracy) of typical office tasks improves with increased ventilation rate. For initial ventilation rates between 6.5 and 15 L/s per person, the average performance increases by approximately 1.0% per 5 L/s per person increase in ventilation rate. At higher ventilation rates, the average performance increase is smaller, approximately 0.3% per 5 L/s per person increase in ventilation rate. For ventilation rates less than 6.5 L/s per person, performance increases with ventilation rate seem likely; however, sufficient data are not yet available to confirm this hypothesis.

Ventilation Rates and School Performance: Increases in classroom ventilation rates up to approximately 10 L/s per student are associated with improvements in student performance of a few to several percent, with the magnitude of the improvement depending on the initial ventilation rate. Increases in ventilation rates up to approximately 7 L/s per student are associated with a higher proportion of students passing standardized reading and math tests. However, data relating ventilation rate with school performance are not extensive.

Ventilation Rates and Respiratory Illness: Substantially higher rates of respiratory illness (e.g., 50% - 370%) in high density buildings (barracks, jails, nursing homes, and health care facilities) have been associated with very low ventilation rates, presumably because lower ventilation rates are likely to result in higher airborne concentrations of infectious viruses and bacteria. Only a few studies have been performed.

Ventilation Rates and Absences in Offices and Schools: In offices, a 35% decrease in short term absence was associated with a doubling of ventilation rate from 12 to 24 L/s per person. In two elementary grade classroom studies, for each 1 L/s per person increase in ventilation rate, absence rates decreased by approximately 1% to 4%. This relationship applies over an estimated ventilation rate range of 2.5 to 15 L/s per person, and should not be applied outside those limits. Data relating building ventilation rates and absence rates are very limited.

Ventilation Rates and Sick Building Syndrome Symptoms: Many studies have found that occupants of office buildings with above-average ventilation rates (up to 20 L/s per person) have 10% to 80% fewer sick building syndrome (SBS) symptoms at work. A statistical analysis of existing data has provided a central estimate of the average relationship between SBS symptom prevalence in office workers and building ventilation rate. This analysis indicates a 23% increase in symptom prevalence as the ventilation rate drops from 10 to 5 L/s per person and a 29% decrease in symptom prevalence rates as ventilation rate increases from 10 to 25 L/s per person. The uncertainty in these central estimates is considerable.

Ventilation Rates and Health in Homes: Very little research has been conducted on the relationship of ventilation rates in homes with the health of the occupants of the homes. The results of a few studies suggest that children in homes with low ventilation rates have more allergic or respiratory symptoms compared to children in homes with high ventilation rates. There is also indirect evidence that ventilation rates of homes will affect health by modifying the indoor concentrations of a broad range of indoor-generated air pollutants.