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What’s the Best Air Filter for Arizona’s Allergy Season?

Monsoon season is here in Arizona which means it’s also...allergy season.

Thankfully, the right HVAC air filter can provide sweet relief from allergy symptoms when you’re inside your home. So what’s the “right” filter when it comes to reducing seasonal allergies?

Well, according to ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers), the best filter for reducing seasonal allergies is a filter with a MERV rating of 10.

We’ll explain what MERV is and why you should look for a filter with a MERV rating of 10. But first, let’s take a closer look at what causes Arizona’s allergy season in the first place.

What causes seasonal allergies in Arizona?

In Arizona, seasonal allergies are primarily caused by:

  • Dust
  • Mold spores
  • Pollen (from trees, grasses, weeds)

You see, when you inhale any of the items above, your body views them as dangerous, foreign objects. And, as a defense mechanism, your body releases “histamines”.

Think of these histamines as bouncers in a club that kick out troublemakers (the allergens). When histamines are released, they immediately tell your body to:

  • Sneeze
  • Tear up
  • Itch
  • Produce extra mucus (i.e. a runny nose)

Basically, histamines do whatever it takes to push air pollutants out of your body.

Why certain filters help reduce allergic reactions in the house

Because your HVAC filter is designed to trap air pollutants, they can help remove the dust, mold spores and pollen that cause your allergies in the first place.

But not all filters are created equal when it comes to catching airborne particles.

You see, every HVAC filter has a MERV rating anywhere from 1 to 16+. A filter’s MERV rating tells you what size particles the filter can capture. The higher the MERV rating, the smaller/finer the particles it can catch.

So what MERV is required to trap allergens like dust, pollen and mold?

Well, first off, let’s look at the size of these allergens. According to the EPA (Environmental Protection Agency), typical allergens like dust, mold and pollen are all smaller than 10 μm (microns).

Allergen Particle Sizes

This image showcases how small dust/pollen/mold are compared to a human hair or a grain of sand.


So what MERV captures particles as small as 10 microns?

Well, according to ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers), filters with a:

  • MERV rating of 10 captures 80% of particles <10 microns
  • MERV rating of 11 to 13 captures 85% to 90% particles <10 microns
  • MERV rating of 14 to 16 captures 95% of particles <10 microns

Judging from the MERV comparisons above, you’d probably be tempted to go with a higher rating than MERV 10, right? MERV-14+ filters capture up to 95% of dust, mold and pollen.

But here’s the thing: filters with a MERV higher than 10 are harmful to most HVAC systems. We’ll explain why...

Why we don’t usually suggest anything higher than MERV 10

The bottom line:any filter with a MERV higher than 10 can “suffocate” your HVAC system.

Think of an HVAC filter as a doctor’s surgical mask. Just like a surgical mask stops harmful airborne diseases from entering the doctor’s lungs/body, a filter stops dust/mold/pollen particles from circulating into your HVAC system and throughout your home.

But a filter with a MERV that’s too high can actually make it harder for clean air to pass through the HVAC system (i.e. your system quickly suffocates). And when your HVAC system can’t breathe efficiently, expensive parts of your AC/heating system get overworked, which leads to frequent repairs and high energy bills.

The answer? Choose a thick, pleated MERV-10 filter instead of anything higher.

A MERV-10 filter that’s at least 3 inches thick and pleated will capture up to 80% of the allergens in your home which will greatly reduce your allergic reactions. Plus, a MERV-10 filter won’t suffocate your HVAC system (as long as you change it every 3-4 months).

Note: The thicker the filter, the more allergens it can catch before clogging and the less likely the filter will create a pressure drop in your HVAC system.

Have more filter or indoor air quality questions?

We’re here to help. We can give you professional recommendations on the indoor air quality products that will get you through Arizona’s long allergy season.