CADR takes into account air leakage, the small amount of particles the HEPA does not filter out, and how often the air purifier cleans previously cleaned air.
Another way to think about it is that a strong fan with no filter may have a high airflow number, but is not producing any clean air (CADR=0).
Also consider real-world tests:
CADR tests are done in labs, so don’t necessarily tell the performances in the real world. We recommend comparing CADR and the data from real-world tests when choosing an air purifier.
Learn more about: How to choose the best air purifier »