AHAM Certified Air Purifiers

How CADR Ratings Work

A CADR rating isn't a single number -- most certified units carry three separate ratings, one each for tobacco smoke, dust, and pollen. That's because particle size varies a lot between these three, and a filter that's excellent at capturing large pollen grains won't necessarily perform the same on much smaller smoke particles. When you're comparing units, it's worth looking at the specific CADR number for the pollutant you care most about rather than treating the ratings as one combined score.

Using CADR to Size a Unit for Your Room

AHAM publishes suggested room sizes based on CADR, and it's a solid starting point. As a general rule of thumb, a purifier's CADR should be at least two-thirds of your room's square footage for effective coverage. That said, real rooms vary in ceiling height, airflow, and how the space is actually used, so we're always happy to help you match a CADR rating to your specific space rather than relying on the room-size chart alone.

Related Reading

• Air Purifiers for Tobacco and Smoke
• Air Purifiers for Wildfire and Forest Fire Smoke
• Air Purifiers for Pet Dander and Odor
• Air Purifiers for Allergies and Asthma