Dyson uses their own private in-house test instead of the industry-standard CADR test to rate their air purifiers. They explain that the CADR rating is not useful as the tests are performed in a lab room, which is very different from a real-world room.
This is true, however the CADR test still holds value. It allows users to compare different purifiers in a standard way and make informed choices on which air purifier is best for them. CADR ratings are an easy and simple way to compare purifiers. Think of CADR like the ‘wattage’ of a lightbulb. A lightbulbs wattage allows you to easily compare different lightbulbs with each other. Sure, it doesn’t tell you everything, but it’s a good start.
CADR ratings should also always be used alongside data from real-world tests, in order to get the fullest picture about an air purifier.
Dyson also got a few other facts about CADR wrong in their marketing. Such as claiming the CADR test cannot test for gases, and that the CADR test does not provide efficiency ratings for different sized particles. Both these claims are wrong.