The three most common approaches to air purification systems are:

Source Control
The first approach -- source control -- involves minimizing the use of products and materials that cause indoor 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 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 airflows in mechanical ventilation units, and opening windows, especially when pollutant sources are in use.

Air Purification Systems
The third approach -- is the best method used to supplement source control and ventilation. Filters, electronic airborne 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 airborne pollution. These methods include eliminating or controlling pollutant sources, increasing outdoor ventilation, and using proven methods of cleaning airborne contaminants.