The Minimum Efficiency Reporting Value (MERV) is a nationally recognized system used to evaluate air filters, and it ranges from 1 to 20. This rating is determined by testing 12 particles of different sizes, from 0.3 to 10 micrometers (µm) in diameter, in a laboratory environment. The particles are divided into three different size ranges (E1, E2 and E3) and four subranges that exist within each range. The first range, E1, includes particles with a size of 0.3 to 1.0 μm.
E2 includes particles of a size of 1.0 to 3.0 μm, and E3 encompasses particles of a size of 3.0 to 10.0 μm. According to the U. S. Environmental Protection Agency, a MERV rating of 5 to 8 can capture and remove particles that could otherwise be harmful to health. A MERV rating of 5 to 8 effectively captures pollen and other particles ranging in size from 3.0 to 10.0 microns, while a MERV rating of 9 to 12 is sufficient to capture particles smaller than 1 and no more than 3 microns.
The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) determines the MERV rating through a series of tests. A higher MERV rating often means lower airflow, which can make the system work harder and use more energy to do its job. You can check your HVAC system's owner's manual to determine the appropriate MERV rating for your system, or consult an HVAC professional for advice. Filters with a MERV rating of 17 to 20 tend to be bulkier because they are designed for heavy-duty filtration, such as in manufacturing buildings. If you want to save money on your energy bills, a filter with a MERV rating lower than 7 would be ideal. One of the best ways to determine which MERV classification you should use is to compare the options side by side. It's best to follow the oven manufacturer's recommendations or consult an HVAC professional for advice on which MERV rating is best for your specific system.
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