The most important things to know about air cleaners are:

• They cannot be used by themselves to clean the air. Pollutants have to be controlled at their source, and indoor air has to be well ventilated.
• Air cleaners have to be well maintained. Dirty air filters, for example, are not going to help you clean the air.
• Buy the right size of unit for the space you want to clean. The airflow should be sufficient to exchange the air in the room five or six times per hour; therefore, the size and efficiency of the filtering device should be determined in part by the size of the room. Do not waste your money buying models that sit on a table or hang around your neck.
• Make sure the unit you buy does not emit more than 0.05 ppm of ozone.