AHAM’s standard for measuring a filter’s efficacy is the Clean Air Delivery Rate (CADR). The CADR indicates the volume of filtered air an air cleaner delivers, with separate scores for smoke, pollen and dust. The higher the CADR number for each pollutant, the faster the unit filters the air.
Always look for the AHAM Verifide® seal when shopping for air filters, which is usually found on the back of an air cleaner’s box.
Follow the 2/3 Rule
As a rule of thumb, the CADR of your air filter should be equal to at least two-thirds of the room’s area.
For example, a room with the dimensions of 10 feet by 12 feet has an area of 120 square feet. It would be best to have an air cleaner with a smoke CADR of at least 80.
Using an air filter with a higher CADR in that room will simply clean the air more often and faster. If your ceilings are higher than 8 feet, an air cleaner rated for a larger room will be necessary.
For more technical information, download the report Method for Measuring the Performance of Portable Household Electric Room Air Cleaners; Understanding its Scope and the Related AHAM Industry Certification Program