Filters have ratings and a well rated filter can make a big difference in the cleanliness of the air circulated through your house. We’ve explained these ratings below to help you better understand what to look for when replacing the filters throughout your home.
Clean Air Delivery Rate (CADR) – The CADR is a measurement of performance of an air filter in removing particles from a given space. It is calculated by multiplying the fraction of particles that have been removed times the CFM (cubic feet per minute) air flow rate through the filter. It sounds complicated, but the Association of Home Appliance Manufacturers makes it simple for customers by placing their AHAM Certified seal on the filter. Their seal has a rating for the filter’s performance in removing particles from 3 different sources: dust, tobacco smoke, and pollen.
Minimum Efficiency Reporting Value (MERV) – The MERV rating is like the CADR measurement in that it ranks an air filter’s ability to trap particles of varying sizes on a scale of 1-20. A filter with a MERV rating of 16 captures more than 95% of particles on a given pass. This handy dandy rating was created by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). For a deep dive into the MERV parameters you can check out the Residential Air Cleaners section on the EPA’s website. Table 2 has a great breakdown of each of the ratings and corresponding particle size captured.
Replacing your air filters is an important step in keeping good air quality in your home. A filter with the best CADR and MERV rating doesn’t mean you don’t ever need to replace it. Also, keep size in mind when replacing your filter. Be sure to look at the measurement of the current filter in your system before you head to the store. Home Depot has a great filter buying guide that can help you with the process.
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