Does Air Conditioning Improve Air Quality?

With today’s polluted environment and airtight homes, anything in your home that can improve indoor air quality matters.

Your air conditioner seems to run constantly, so it’s obvious to ask whether your air conditioning can also improve air quality? In the majority of homes, the air conditioner does not improve air quality, at least not to an extend that would have an impact on one’s health. Only when highly rated MERV filters and ductwork adaptations are added can an air conditioning system be able to significantly improve the air quality in a home. And even then, it will likely have to be supplemented by an air purifier and dehumidifier.

Now that you know what your air conditioner is and isn’t capable of, let’s take a look in more detail what changes you can make to make it more likely to improve the air in your home as well.

Why Your Air Conditioner Doesn’t Really Improve Air Quality

The main purpose of your air conditioner is “comfort.” In other words, it’s there to keep the humidity and temperature down so you feel comfortable and aren’t breathing in sticky or dry air. Any other air-purifying benefit is considered only secondary.

In that sense, it is improving air quality, but there’s more to air quality than just humidity and temperature.

Besides those, any system that can be defined as having the ability to improve indoor air quality must address the various pollutants in the air. Those range in various sizes, from small gaseous molecules that can get lodged in your lungs and bloodstream known as volatile organic compounds (VOCs) to larger pollutants like dust mites and pollen.

And to trap or remove the majority of those pollutants, any air filter must either be extremely fine or be able to cause a physical or chemical reaction with the pollutants (such as adsorption or ionization).

The Types of Filters Most Homes Typically Use

The Typical Fiberglass Air Filter

The typical cheap fiberglass air conditioner filter is only mechanical. Its purpose isn’t to clean these fine pollutants from the air, but rather, to just trap larger particles like wood, stone, hair, carpet fibers, and some of the large dust or pollen particles.

Its real purpose is to protect the furnace from damage by trapping those large particles.

Another purpose is to improve energy efficiency so you get a lower energy bill at the end of the month. Sounds great, except that in order to push more air through and be more energy-efficient, it typically also means that the filter needs to be thinner and more permeable to pollutants.

Better air flow equals better energy bill.

Which brings us to something called a MERV (minimum efficiency reporting value) rating.

MERV Ratings

A MERV rating essentially is a measure of how good a filter is at filtering various particles compared to how well it maintains the air flow. The cheapest fiberglass filters are generally rated at only about MERV-1 to MERV-3. They’ll filter out some dust, pollen, and mold. Emphasis on some, as only the larger of these particles will get trapped.

Higher MERV-rated filters can filter out even the smaller pollutants at the expense of reducing the air flow. However, those are usually used in powerful commercial-grade air conditioning units like in hospitals. For residential use, you’ll need a filter that’s a grade above the cheap fiberglass filter, yet won’t restrict air flow too much.

Yes, we’re now talking about pleated filters.

On the lower end of the spectrum, the MERV-8 filter will be a major upgrade to the fiberglass filter. It will be able to pick up more of the larger pollutants like dust mites and some mold spores. My favorite for my home, the MERV-11 filter is able to pick up the rest of the dust particles and is great for homes with a lot of pet dander. It doesn’t restrict air flow too much.

MERV-13 is nearing more towards commercial-grade and can help you with bacteria, viruses, tobacco smoke, and cooking oil smoke, but remember that it will restrict air flow if your air conditioning unit isn’t powerful enough.

Converting MERV Ratings

MERV ratings go from 1 to 16. Anything up to MERV-11 will be reaslistic for a residential home, and even a MERV-13 filter could technically work with a more powerful air conditioning unit.

But not every air filter manufacturer and retailer uses MERV ratings.

3M filters use something called an MPR (micro particle performance rating), which primarily focuses on the particle sizes it can filter. FPR (filter performance rating), as the name implies, looks at how well a filter works in a given air conditioning system. You’ll find FPR if you purchase your filters at the Home Depot.

But don’t let these ratings confuse you. You can use the simple examples below to find the closest MERV equivalents.

MERV-6

Similar to:

• MPR 300
• FPR – too low to rate

What it means for you:

• These filters can only trap larger particles, roughly 3 microns in size and larger. Will trap large particles like dust, lint, pollen, and only some minor pet dander.

MERV-8

Similar to:

• MPR 600
• FPR 5

What it means for you:

• Intermediate filter that can pick up the rest of the dust and pollen, as well as about half of pet dander. Can also trap some mold spores.

MERV-11

Similar to:

• MPR 1,000 o MPR 1,200
• FPR 7

What it means for you:

• A great filter to alleviate respiratory effects of pollutants, usually has only a slight effect on air flow on air conditioning unit. Besides picking up the rest of pet dander, can also pick up some lead particles, smaller dust that irritates the respiratory system, the majority of bacteria, and some tobacco and cooking oil smoke.

MERV-13

Similar to:

• MPR 1,500
• FPR 10

What it means for you:

• This filter will pick up the rest of the smaller particles and is sensitive enough to even pick up viruses and smog, although it’s considered commercial grade only.

What About Electrostatic, HEPA, and Activated Carbon Filters?

You might be wondering about other filter options like electrostatic or HEPA filters.

Electrostatic filters have great appeal since they can be washable, although how long they really last is up for debate with some manufacturers. These filters typically only have a mesh of metal that trap pollutants electrostatically.

They’re an obvious option (and certainly an upgrade compared to some lower quality filters), just keep in mind that these filters rarely have a MERV rating above 8.

You might have also heard about HEPA (high efficiency particulate air) filters. Those are on the other side of the spectrum and most would even exceed an equivalent MERV-16 rating if one were to exist. HEPA filters usually aren’t made for air conditioning purposes since they would severely restrict air flow.

When they are added on, it’s usually through some modified ductwork that can only bypass the main system only. The air is pulled from the main system into a bypass duct, processed through the HEPA filter, and reintroduced back. There are also other solutions that can added on here, like adding in fresh air return ducts to introduce fresh air from the outside. This not only prevents the same stale air from recirculating, but also alleviates some pressure off your system, keeping it more efficient and prolonging its life.

Some MERV filters have an activated carbon filter mesh built into them. This helps trap some of the smaller particles like smoke and VOCs. It probably is true in most cases, just keep in mind that a thin spray-on carbon layer will be less potent than a filter with actual carbon granules inside.

The Role of Humidity

Humidity is a large factor when it comes to air conditioning and air quality for that matter.

Your air conditioning system works by removing humidity from the air. The drier the air is kept, the cooler the room temperature can be. This is why hot air typically is sticky (humid). If the humidity in your home is off balance and a faulty air conditioning system is left unchecked, it will cause an even worse problem – mold.

For that reason, it’s imperative to keep the humidity in your home under control if you want your air conditioner to last and run properly.

If you notice your air conditioner is struggling to keep up during a humid and warm summer, help it out by introducing a dehumidifier to your home. Here’s out guide on how to choose one.

You could also have a dehumidifier attached directly into the air conditioning system rather than to have a clunky free-standing unit that plugs in. Although, this typically costs thousands of dollars to have done.

And Always, Don’t Forget the Air Purifier

An air purifier can work together with your air conditioner to improve air quality in your home. If you choose the right air purifier, you’ll be able to eliminate the smaller particles, as if your home had a MERV-13 air conditioning filter.

In fact, an air purifier with a HEPA filter in addition to an activated charcoal filter will far exceed what a highly rated air conditioning filter can do. Although, keep in mind that just one air purifier won’t be able to cycle the air in an entire home like an air conditioner would. There are whole-house air purifiers, but it will be a major investment and isn’t for everyone.

Here are some resources to help you choose the right air purifier:

• How Many Air Purifiers Do I Need?
• Should I Get a Whole House Air Purifier?
• Best (Affordable) Air Purifiers For Indoor Air Quality

What You Can Do to Turn Your Air Conditioner Into an Air-Purifying Machine

Hopefully, by now you know some changes you can make to allow your air conditioner to purify the air rather than just to cycle cool air.

Obviously, an air conditioner by itself will never be an actual air purifier, but here are a few things you can do to improve the air quality in your home with it.

So in conclusion, I’ll recap a few of those ideas:

• Go for higher MERV-rated air filters. Hopefully, I’ve convinced you that MERV-11 is the right rating for most residential homes.
• Consider adding ductwork or other modifications in your air conditioning system; for example – HEPA filters and fresh air return ducts.
• Obviously, changing out your filter regularly. Maybe it’s time to change it every 1 or 2 months instead of 3 to 6 months?
• Add an air purifier or two across the home to help.
• Turn on a dehumidifier from spring to early fall, especially if you live in a humid climate or have a basement.