lets first understand what is CADR. CADR is Clean air delivery rate. As you may have understand we are talking about portable air purifier/ air cleaners clean air delivery rate. CADR is specific to pollutants of specific size. For example if i am talking about a portable air purifier unit And said its CADR is 450 CFM (Cubic feet per minute) Which means it cleans 450 Cubic feet air in a minute.
But the statement will be complete with one more line. It clean dust/pollen/smoke any of these particle with 450 cubic feet per minute rate. (Not the complete air pollutants only one specific pollutant) I hope i am able to make you understand CADR is not meant for all air borne particles (Which lots of air purifier manufactures hides) they show their Air flow as CADR value. Which is wrong.
Why Clean air delivery rate
AHAM, Usa first find a test ANSI/AHAM-AC-1 where they test air purifier in a small room and test with 3 common air pollutants which you may find in your home commonly DUST/Pollen and smoke. because there is no way we can filter out gases so no test attempt on it. This test tells about air purifier filters capability to filter out air on these three major air pollutants and gives report about how much faster these air purifiers capture these pollutants.. It also provide the information about coverage area the machine covers with effective 5 air changes in an hour.