Designed by the Association of Home Appliance Manufacturers (AHAM, the Clean Air Delivery Rate (CADR) is the volume of filtered air delivered by an air purifier. It measures three factors; smoke, pollen, and dust. The higher the number, the better. Along with these numbers, will be a suggested size of the room that the air purifier in question will clean. You’ll want to be sure that the air purifier you buy, can handle the room you plan on placing it in. Higher number ratings, for each of the three factors; smoke, pollen, and dust, means the purifier will filter the air faster than when these numbers are lower. You can read a bit more about the (CADR) here.
Consumer Reports released an air purifier buying guide that not only helps you select the right purifier for your specific needs, but also provides some tips to reduce indoor air pollution.
Live Science wrote an article that outlines the best air purifiers and also provides some specific tips for those suffering from allergies as well as pet-specific allergies.
James, from Plenty Air wrote an article reviewing the top 20 air purifiers for 2016. In the article are some explanations for other factors to take into consideration when buying an air purifier.
I hope this article helped you to better understand the health benefits of having an air purifier, and helped with some further resources to do comparisons of air purifiers.