Frequently Asked Questions What is the CADR specification in my Philips Air Purifier? If you would like to know what the CADR specification mentioned in your Philips Air Purifier's package or leaflet is, read about it here. 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.