Understanding an Air Purifier's CADR Rating

A practical estimate is:

Recommended room area ≈ CADR × 0.1

For example, a 20 m² room generally requires a CADR of at least 200 m³/h.

The current standard distinguishes between two CADR values: one for particulate matter, such as PM2.5 and dust, and another for formaldehyde.

Air purifiers use different materials and mechanisms for different pollutants, so a single model may have very different CADR values for PM2.5 and formaldehyde.

Manufacturers often display the particulate CADR prominently, while the formaldehyde CADR may be less visible or even omitted from some product information. This can create the impression that a purifier performs equally well against every pollutant. A capable all-round purifier should maintain a reasonably strong formaldehyde CADR even if particle removal is its main strength, except for models designed for only one purpose. When choosing a purifier, review the complete test data rather than relying on a single headline number.

Although air purifiers can reduce formaldehyde, their capacity is limited. Formaldehyde removal relies mainly on activated carbon, which works by adsorption. Once the carbon becomes saturated, it may release previously captured formaldehyde. Strong, sustained ventilation remains the fundamental way to reduce formaldehyde when outdoor conditions allow.