Frequently Asked Questions What is the specification CADR in my Philips Air Purifier? If you would like to know what the specification CADR mentioned in your Philips Air Purifier’s package or leaflet is, read here about it. What is CADR? CADR stands for Clean Air Delivery Rate. It indicates the volume of filtered air delivered by your Philips Air Purifier. Your Air Purifier will run faster when the amount of particles, tobacco smoke, pollen and dust increases.