Do I Need an Air Purifier if I Have AC? AC vs Air Purifiers

That air conditioner hanging from the window of your apartment has a filter, likely a thin layer of foam attached to the inside of it. So does the central air unit that pushes refrigerated air through the ducts of your home, only it’s probably a cellulose or fiberglass style that slides in next to the main ductwork.

They’re filters, right? Why should you worry about an air purifier if you already have filters working with your air conditioning unit?

“Do you need an air purifier if you have AC?” is a thought many homeowners and renters have when they think about air quality.

The answer to the question do I need air purifier if I have AC is emphatically, yes.

What is an air conditioner?

There are two types of air conditioners, the window mount, and the central air system. Both work by pumping cold air into a room, and hot air out. If you want to feel the process all you have to do is stand inside a room next to the incoming airflow and feel the cool air, then go outside and feel the hot exhaust being driven out of the air conditioner into the surrounding environment.

They are essentially heat exchangers that force air over Freon-filled, refrigerated tubes via a fan, cooling the room.

They are designed to lower humidity and lower temperature simultaneously.

Step back outside and watch the water drip out of a window mount air conditioner. What you’re seeing is the humidity removed from the inside air.

The byproduct is distilled water. Water that is dripped to the ground or an underground drain via a drain tube.

Air conditioners have a rudimentary filter system to protect the unit, but they’re not designed to purify the air.

Window mount air conditioners

Let’s take a look at what the filter on an air conditioner is designed to do. On a window mount unit, it prevents dust, pollen, and plant residue from entering the room.

If you’ve ever taken a look at a window mount air conditioner on a late spring day you’ve probably noticed a heavy layer of what looks like lint covering the fins on the evaporative unit at the back of the air conditioner. It’s not lint, but something similar.

Pollen, plant dander, and in the West and Midwest it’s the cotton from the cottonwood trees that dominate the landscape.

If you leave it, the performance of your air conditioner will diminish, it will heat up, take more electricity to run, and become less efficient. That’s just the airborne particles you can see.

The filter just behind the fins blowing air into your room captures smaller particles, but it can’t catch them all, and it sure can’t compete with the air cleansing capabilities of a dedicated air purifier.

Central air conditioners

Central air works the same way, only on a larger scale. The compressor/condenser assembly that sits outside your home can have the entire evaporative unit covered with the same airborne particles. It will diminish the cooling effects of your household system quickly and can overheat and damage the unit.

Once the air is spun inside your home it is forced through a cellulose or sometimes spun fiberglass filter before it enters the ductwork.

In most homes, the same filter works with the heater in winter as it does with the air conditioner in summer. It can be packed with dust after just a few days, but is it really purifying the air?

Once, again, the answer is no. The most complex, expensive air conditioning systems on the market can’t compete with the air cleaning process taking place with an air purifier.

What is an air purifier?

An air purifier is a device solely dedicated to improving air quality inside a room, or an entire home. They remove airborne particles and contaminants from the air.

The benefits to everyone are obvious, but if a person has a compromised immune system, is prone to respiratory illness, or suffers from allergies, the benefits are much more valuable.

Air purifiers remove dust, smoke, mold spores, pollen, bacteria, pet hair, and dander, and can even remove odors.

There are two primary styles of air purifiers, the HEPA filter, and the Ionizer. They can work as a standalone device in a single room, or like the central air conditioner, they can purify an entire home using the existing ductwork in an HVAC system.

HEPA filter purifiers

A HEPA filtering system forces air through a filter, or series of filters to trap pollutants. There are various ratings of HEPA filters, with the best claiming a success rate of 99.97% in capturing pollen, dust, bacteria, etc. from the air.

HEPA filters do a good job of purifying the air, but they must be monitored and changed to be effective. They can become clogged with airborne particles, rendering them useless.

Most modern HEPA systems have a built-in alarm that lets you know when the filter needs to be changed.

They work very well in single rooms, where they should be placed away from the primary occupation area. In laymen’s terms, keep the filter across the room from your bed or from the desk where you spend most of your time.


If you like to see something working, you’ll love an ionizer. The results are a sudden increase in the dust on furniture and wood surfaces around your room.

Ionizers work by applying a negative charge to the pollutants in the air. This removes them from the air by making them adhere to the positively charges items in your room, hence the dust buildup.

That extra layer of dust on the top of the refrigerator or dresser might be annoying, but remember that was floating in the air before you had an ionizer and you were breathing that directly into your lungs.

Ionizers don’t have filters, so they don’t need monitoring as HEPA systems do. They do produce dust and they have another caveat to be aware of, ozone generation.

Ozone is dangerous, while it has anti-bacterial properties, it can build up to dangerously high levels when left running continuously.

An ionizer should never run 24/7 and should never run while you’re sleeping.

Ionizers work well in large buildings, and in central air purifying systems, but are heavily regulated as a standalone device.

They’re cheaper to operate since they have no consumable components, like filters, but they require close maintenance and well-placed ozone sensors in a home.

Do I need an air purifier if I have AC?

After reviewing the capabilities of air conditioners and air purifiers, do you need an air purifier if you have AC?

Yes, you do.

Lowering humidity and cooling a room or a home on a hot summer day is one of the niceties of modern existence, but that lower humidity and cool air isn’t free of bacteria, pollen, pet hair, smoke, or smell, to get to that state requires an air purifier.

Air purification is essential in the modern world where industrial-based pollutants commonly float in the air.

Bacteria, smoke, pollen, pet dander, and even skin cells from other people float on the air we breathe.

If you’re lucky enough to have no allergies at all, you won’t notice much difference with an air purifier, but if you’re like most of us, and have allergies to the wide variety of things that float invisibly in the air, you’ll notice the difference immediately.

Commercial airliners have specially designed air purification systems that can completely recycle and cleanse the air in the passenger cabin and crew compartments every three minutes while in flight.

The FAA and commercial airlines take air purification seriously for their passengers.

Large public buildings like libraries, museums, and even indoor sports stadiums filter the air through huge fans and extensive ductwork for the same reason.

That swooshing sound you hear when you enter a building with revolving doors is the air rushing in to equalize pressure between the inside and outside of a building. It is evident that a purification and air conditioning process is present and working simultaneously.

The three “P’s” of air quality

“P’s”Air ConditionerAir Purifier
PrimaryLowers humidity, coolsCleans air, removes odors, reduces bacteria and allergens
PositivesComfortLowers allergen exposure
ProcessRoom / CentralHEPA / Ionizer

Air conditioners and air purifiers a winning combination

Rather than looking at air conditioners and air purifiers as competitors, you as a homeowner or renter should see them as partners in a mutual effort to make life better for you.

Humans have always heated homes in the winter, but in the last century with advancing technology we’ve been able to cool them in the summer too.

Witness the expansion in Texas, Arizona, Southern California, and Las Vegas in particular. Without air conditioning, you wouldn’t have that influx of people.

Stepping the game up with air purifying combined with air conditioning creates not only a comfortable environment but a safer one as well.

Use the two technologies together, and reap the benefits.