Why is CADR Used Instead of Airflow in Calculating Air Changes per Hour (ACH)?

Using CADR for ACH calculation is a more conservative, safer approach. If an air purifier’s air flow were to be used to calculate its ACH, it would assume that the air purifier is doing a perfect job of cleaning every part of the air in the room. In reality, some of the same air will pass multiple times through the purifier before all the air in the room is cycled through.  CADR helps take into account this factor. 

Learn More: Air changes per hour (ACH) and how to calculate it » 


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