The three most common approaches to efficient air purification:

Source Control
The first approach -- source control -- involves minimizing the use of products and materials that cause indoor air pollution, employing good hygiene practices to minimize biological contaminants (including the control of humidity and moisture, and occasional cleaning and disinfection of wet or moist surfaces), and using good housekeeping practices to control airborne particles.

Ventilation
The second approach -- outdoor ventilation -- is also effective and commonly employed. Ventilation methods include installing an exhaust fan close to the source of contaminants, increasing outdoor air flows in mechanical ventilation units, and opening windows, especially when pollutant sources are in use.

Air Purification
The third approach -- airborne contaminant purification -- is the best method used to supplement source control and ventilation. Air purification filters, electronic particle cleaners and ionizers are often used to remove airborne particles, and gas adsorbing material is sometimes used to remove gaseous contaminants.

Recommendation
The public is advised to use proven methods of controlling indoor pollution. These methods include eliminating or controlling pollutant sources, increasing outdoor ventilation, and using proven methods of cleaning airborne contaminants.

Conclusions
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 airborne contaminant cleaners are effective in removing certain indoor pollutants. Thus, as an adjunct to effective source control and adequate ventilation, highly efficient airborne contaminant cleaners can be useful in further reducing levels of certain indoor airborne pollutants. More research on the health benefits of air purification systems is needed to provide complete evidence that would better address the circumstances of intended use.