Many air purifier makers will state very high CADR (Clean Air Delivery Rate) to promote their products.
Some even exaggerate the spec sheets and claim they can remove 100% contaminants.
Just look at the size of the air purifier & how big is the filter in use? Is it really logic to match the CADR & claims they made?
Better do some studies not by just listen to what they claim.

For CADR you can check at http://www.ahamdir.com/aham_cm/site/pages/...boutThisProgram
AllergyUK also certify air purifier for what the manufacturer claims http://www.allergyuk.org/products-and-serv...g/air-purifiers