There are many air pollutants, both indoors and outdoors. Automobile emission and industrial discharge are one of the well-known polluting sources, and many other polluting sources are ignored by the people, such as bacteria, mold, dust mite, pollen, domestic cleaning detergent, daily cleaning products, paint remover, cigarette, thick smoke released by combustion of gasoline, natural gas, wood or carbon, and even decoration materials and building materials themselves. A research by EU shows that, many ordinary articles at home are main sources of volatile organics. Of them,formaldehyde, benzene and naphthalene are three worrying harmful gases. Besides, some organic compounds react with ozone to produce secondary pollutants, such as fine particles and super-fine particles. Some secondary pollutants lower indoor air quality obviously and bring pungent odors.

To remove air pollution efficiently, there are three approaches available: 

1. Remove polluting source or control pollutant discharge;

2. Ventilation equipment;

3. Air purifier

Removal of polluting sources or control of pollutant discharge is not a simple choice, in particular to urban area. Comparatively, air purifier is a simple and feasible approach.