MERV Ratings and How to Use Them

Don’t you just love acronyms? MERV is an especially colorful one, reminding us – if you’re old enough – of the funny guy who hosted talk shows and wrote the Jeopardy! theme song. But in the realm of indoor air quality, especially for those of us who suffer from allergies, MERV stands for “Minimum Efficiency Reporting Value” -- whew, that’s a mouthful. In English, MERV really just means, “how well does your air filter work?”

MERV rating was developed by The American Society of Heating, Refrigerating and Air-Conditioning Engineers to indicate a filter’s worst performance possible at removing particles ranging in size from .3 to 10 microns (in other words, really tiny!).

Pollen – 10+ microns

Dust Mites – 10+ microns

Textile and Carpet Fibers – 10+ microns

Mold Spores – 2.0 to 10 microns

Pet Dander – 1.5 to 10+ microns

Dust – 0.5 to 10 microns

Bacteria – 0.3 to 10+ microns

Tobacco Smoke – 0.3 to 2 microns

Most home systems can remove airborne contaminants with filters rated MERV 7-12. Higher rated filters, from 13-16, are usually found in hospital or surgery environments.

Illustration: Filterfast.com

Higher Is Not Better

You might think that a higher MERV rating would automatically be better, but it’s not. The higher the MERV rating, the smaller the pores are for air to flow through an HVAC filter. This can create more resistance in airflow than a system is designed to manage, thus making it inefficient. Reducing the air flow in your system can actually worsen the air quality in your home and put a damaging amount of pressure on the fan of your furnace or AC system. So it is worth doing some research. Find out what the highest MERV rated filter is that still allows for maximum airflow in your system.

May 3rd 2017 Jessica

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