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

Using CADR for air changes per hour (ACH) calculation is a more accurate method.

Using an air purifier’s airflow to calculate the air changes per hour for a given room does not take into account:

  1. Air purifiers do not remove 100% of the particles that pass through the filter. Not all air coming out of the purifier has passed through the filter.
  2. Air may not mix perfectly in a given room. Typically, some air in a room will pass multiple times through the purifier before all the air in the room is cycled through.
  3. There is no standard, well-defined testing method for air purifier airflow. Companies measure airflow differently, making it difficult to compare air purifiers using airflow.

CADR is more accurate because takes all three of these factors into account. CADR tests are also standardized and can be completed by third-party laboratories.

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


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