While shopping for a new air filter, you may have come across this curious phrase: “MERV rating.” So what the heck does it mean?

MERV stands for Minimum Efficiency Reporting Value. Basically, it translates to “This is how efficient an air filter is at catching particles.” MERV ratings are on a scale of 1-16 and measure what size of particles a filter can catch between 10 to .3 microns. To put that in perspective, a single hair is 70 microns in diameter. A high MERV rating means a filter can catch smaller particles and can also catch larger particles more effectively. Here’s why that’s important for homeowners.

How smaller particles affect your family’s health

The obsession with particle size has to do with how smaller particles affect your health. According to the EPA,

“The size of particles is directly linked to their potential for causing health problems. Small particles less than 10 micrometers in diameter pose the greatest problems, because they can get deep into your lungs, and some may even get into your bloodstream. Exposure to such particles can affect both your lungs and your heart.”

So, a filter with a higher MERV rating protects your family’s health from a wider variety of health issues. If you have allergies or asthma symptoms, this especially applies to you.

Different tiers of MERV ratings

These are the 4 tiers of MERV ratings, according to American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) tests:

  • MERV 1-4: A typical cheap fiberglass filter. Catches particles 10 microns and larger—including dust, pollen and carpet fibers. Meant to protect your heating/cooling system—not your health.
  • MERV 5-8: Catches particles as small as 3-10 microns—including mold spores, animal dander and dust mites.
  • MERV 9-12: Catches particles as small as 1-3 microns—including legionella and lead dust.
  • MERV 13-16: Catches particles as small as 1-0.3 microns—including tobacco smoke and bacteria.

Is higher always better? No, not always. Some high MERV-rated filters have smaller pores and therefore restrict airflow in your ducts. This forces your heating/cooling system to work harder to push air through the ducts. It’s the equivalent of you trying to breathe normally through a straw. But some air cleaners can catch 99.98% of particles (a ridiculously high MERV rating) without a high air pressure drop. While air cleaners are allergy and asthma sufferers’ best friend, they’re also the most expensive air cleaning option. So, when buying a high-efficiency air cleaner, what MERV rating should you buy? It depends on your goals. Are you trying to save money? Get cheap fiberglass filters with a 1-4 MERV rating. Is there a particular particle that’s agitating your allergies? Find a filter or air cleaner with a high enough MERV rating to catch those particles.

Need help finding a filter that fits your needs? We can help. Ragsdale Heating, Plumbing and Air has been serving the metro Atlanta area for over 25 years. Contact us online for more information on how we can help you.

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