Certain air purifiers can help provide allergy relief; those purifiers have a Clean Air Delivery Rate, a rating standard developed by the Association of Home Appliance Manufacturers, according to EverydayHealth. It's important to avoid air purifiers that release ozone.
The CADR numbers are usually placed on the back of an air purifier's box, states EverydayHealth. These numbers rate the purification of air with tobacco smoke, dust and pollen. A higher CADR number means that the purifier can clean the air more quickly. It helps to know the room dimensions to select a purifier with the necessary filtering ability. Larger rooms require higher CADR numbers, says EverydayHealth.