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. A Norwegian study [39] of young children found that low home ventilation rates were not associated with an increase in bronchial obstruction (i.e., reduced breathing airflows) in children. However, the increase in risk of bronchial obstruction resulting from other factors, such as building dampness, was moderately to markedly higher in homes with ventilation rates below 0.5 ach. In other words, having low ventilation rates increased the health risks from some of the building conditions, such as dampness, that are associated with indoor pollutant emissions.

A Swedish study [40] of 390 single family homes found that children in homes with very low ventilation rates (0.05 to 0.24 ach) had twice as many allergic symptoms compared to children in homes with high ventilation rates (0.44 to 1.44 ach). However, a statistical test indicated that this finding had more than a 5% probability of being a chance finding. Another Swedish study [41] found that the risk of recurrent wheezing in children was not different for houses with measured air exchange rates above and below 0.5 ach.

One additional residential study [42] found that the risk of having asthma symptoms was increased in homes with higher indoor carbon dioxide concentrations which are indicative of less ventilation per person. Statistical tests indicated less than a 5% probability that this finding was a chance finding, However, the study relied on only 60 minutes of carbon dioxide data in each house and such limited data may not be a reliable indicator of long term average ventilation rates.

Dormitory rooms serve as the homes of many college students. A study of college student dormitory rooms in China [43] found that the proportion of students with a very high frequency of common colds, more than six colds per year, was diminished in dormitory rooms with higher ventilation rates; however, the reduction in common colds with increased ventilation rate was not quite statistically significant. Some of the rooms had very low ventilation rates, less than 3 cfm per person.

There is also indirect evidence that ventilation rates of homes will affect health. From numerous experimental studies, as well as from theoretical modeling, we know that higher ventilation rates will reduce indoor concentrations of a broad range of indoor-generated air pollutants. Because exposures to some of these air pollutants, for example, environmental tobacco smoke and formaldehyde, have been linked with adverse health [44-47], we expect that increased home ventilation rates will reduce the associated health effects.

In summary, the few studies that have directly investigated whether lower ventilation rates in homes are associated with a worsening of health have had mixed findings. These studies have considered only respiratory health outcomes such as asthma symptoms and wheeze. However, for indoor pollutants that have been clearly linked with adverse health effects, the reductions in indoor pollutant concentrations in homes with higher ventilation rates would be expected to improve health.