Contaminated air is caused by various pollution sources floating in the air. Because of the diversity of pollution sources, a air purifier is relevant at different times. Whereas a person with hay fever symptoms is primarily affected by pollution sources such as pollen in the spring, for a person with asthma symptoms, this is less dependent on the season. But people without allergies also benefit from using a air purifier.

In addition to pollen, a air purifier filters the following substances:
- Fine dust
- Cooking odors
- House dust mite
- Chemicals
- Dander
- Smoke