What is a MERV?
Minimum Efficiency Reporting Value, or MERV, is a scale that rates the effectiveness of air filters. Created by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) in 1987, air filter MERV ratings relate to the relative effectiveness of the filters they’re assigned to.
How Do MERV Ratings Work?
Filters are rated on two different performance factors as measured by testing both the upstream and downstream airflows of a given air-cleaning appliance. The first factor evaluated is how effective a filter is in removing large (greater than 1 micron in size) particles like pollen, pet dander, and byproducts from dust mites. The other factor is efficiency in filtering out particles less than 1 micron in size, such as smoke from cooking or tobacco, household dusts, bacteria, viruses, and even benzene gas. (As a matter of perspective, the eye of a needle (depending on the type of needle, of course) is somewhere in the 500-200 micron range.)
What is the Best MERV Rating for Your Needs?
Given that some 98 percent of all indoor air particles are under one micron in size, a filter’s ability to remove these minute yet potentially harmful specks is especially important when it will be used to improve the quality of indoor air. Continue reading →