The efficiency of filters is measured in terms of the particle size that the device can capture. In most cases, very small particles are the ones that penetrate deep into the lungs, causing health problems. Look for mechanical filters such as HEPA filters and air cleaners that can effectively trap large and small particles.

Overall, the American Lung Association recommends that proven source control strategies be employed as a primary means of reducing exposure to pollutants. However, physical studies which do not measure health effects do show that certain filtration systems are effective in removing certain indoor, airborne pollutants. Thus, as an adjunct to effective source control and adequate ventilation, highly efficient filters can be useful in further reducing levels of certain indoor pollutants. More research on the health benefits of all air cleaners is needed to provide complete evidence that would better address the circumstances of intended use. Manufacturers, clinicians, government agencies, and private industries can all assist with providing and interpreting this research in order to better inform the public.

The reality in most residences is that total elimination of a pollutant source is not always possible or practical. Individuals with severe allergy and asthma symptoms, whose symptoms are not alleviated by other source control and ventilation strategies, may want to try an effective filter in an attempt to aid in further exposure reduction. Although there is no proven health benefit from such a measure, some individuals report that they perceive filter as useful in improving their health status.