Minimum Efficiency Reporting Value. This corresponds to you systems air filters. The higher the Merv rating, the finer the filtration, and the fewer dust particles and contaminants can pass through the filter. Pure Air recommends that the customer buys the highest rated filter they can reasonably afford. A higher Merv rating insures that your air handler can stay cleaner longer, resulting in better air quality inside of your home. Pure Air also has an agreement with FilterFetch.com allowing its customers to log in with a company and filter code, making the reorder much easier with shipping to the home.