CADR, explained
The clean air delivery rate, and how to read it.
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What CADR measures
EPA says most portable air cleaners are rated by their clean air delivery rate (CADR). It says the higher the CADR, the more particles the air cleaner will remove and the larger the area it can serve. ENERGY STAR says CADR measures how quickly a unit delivers filtered air.
Smoke, dust, and pollen
EPA says some packaging shows CADRs for three pollutants: tobacco smoke, dust, and pollen. It says these stand for small, medium, and large particles. To remove small particles, EPA says to look for a high CADR for tobacco smoke.
The test method behind it
EPA's technical summary names a voluntary test standard, ANSI/AHAM AC-1-2015. EPA says it was developed by the Association of Home Appliance Manufacturers (AHAM), a private voluntary standard-setting trade association, and is recognized by the American National Standards Institute. We name it only. We do not say any air purifier meets it, was tested to it, or is certified or verified to it.
Measured at the highest speed
EPA says the CADR is typically measured at the air cleaner's highest speed. Its technical summary says the CADR at lower settings may not be known and could be considerably lower.
Particles only
EPA says the CADR rating system is for particles only. It does not rate how well a unit removes gases or odors.
A rating, not a promise
EPA's technical summary says a portable air cleaner may not achieve its rated CADR under all circumstances, but the CADR value does allow comparisons among portable air cleaners.
FAQ
General information only. An air purifier is not a substitute for ventilation, for removing the source of a pollutant, or for medical care. Read and follow the maker's manual. The California Air Resources Board strongly advises against the use of ozone generators in spaces occupied by people or animals. If you have asthma, allergies, or heart or lung disease, talk to your doctor. During wildfire smoke, follow local officials and be ready to evacuate. In an emergency, call 911.
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