How Does An Air Purifier Work? (Do They Even Clean the Air?)

Josh Mitchell

Written By

Josh Mitchell

Expert Reviewed By

Holly Curell

Last Updated On

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Key Takeaways

  • Air purifiers are designed to improve the air quality index of your room by removing dust, allergens, pathogens, and other dangerous particles from the air.
  • Air purifiers work by sucking the particles from the air and capturing them in a series of filters.
  • Air purifiers with HEPA filters are effective for particles that are as small as 0.3 microns. They are less effective against smaller particles such as coronavirus which measures 0.1 microns.

I, like many people, use air purifiers to purify the air in my home. Just judging by the name, it seems pretty obvious what an air purifier does.

However, I always run into people who have never stopped to really think about what an air purifier does or exactly how it works. Even though what they do may seem fairly obvious on the surface, there’s still a lot people can learn about these machines.

Let’s dive deep into these air-cleaning machines and uncover what exactly they do and how they work.

What Exactly Does An Air Purifier Do?

Air purifiers are designed to remove airborne pollutants, including dust, pollen, smoke, pet dander, bacteria, and viruses, from the air inside your home. They use filters or other methods to capture and remove these contaminants from the air.

I’ve worked with a lot of people who are under the impression that outdoor air is dirtier than indoor air. However, indoor air pollution can be 2-5 times worse than outdoor air! This is why air purifiers are so important.

Their effectiveness depends on factors like the quality and type of the unit and the indoor environment. To ensure the air purifier continues to operate effectively, it’s essential to perform regular maintenance and replace the filters as needed.

How Air Purifiers Operate To Clean The Air

Air purifiers have an internal fan system that pulls in air from the room. The air passes through various filtration and sterilization methods before being released back into your home.

Some pollutants stick to hard surfaces in your home, but most airborne contaminants will eventually make their way into the air and through the air purifier’s system. Running an air purifier continuously for anywhere from 4 to 24 hours can purify the air in your home environment. I usually leave mine on all day.

However, it’s essential to place the purifier correctly and ensure enough room for airflow and proper circulation. With the right setup, your home’s air can be purified in just one day and continue as long as the purifier is running.

Related Article: Are Air Purifier Safe?

Filtering Properties

Air purifier filters come in various types, sizes, and styles. They are designed to capture and remove various pollutants, from dust and dander to mold, bacteria, and viruses.

Air purifier filters can catch almost microscopic particles. For example, human hair has a diameter of 70 microns, indoor allergens, and bacteria range from 2-5 microns and 3 microns, and viruses are even smaller, measuring 2 microns or less.

Air purifiers use high-density fibers, a deep-woven mesh, and other materials to capture anything as small as 1 micron from passing through. A standard paper HEPA filter in a central AC unit can only trap particles as small as 3 microns.

Effectiveness And Purifier Needs

The effectiveness of air purifiers depends on what you’re looking for and what types of pollutants you’re trying to eliminate. I used my air purifier during the recent pandemic to help protect against the coronavirus. The coronavirus is typically about 0.1 microns in size.

While the virus is too small to be captured by most air purifiers, it can become airborne by attaching to larger particles like water droplets or aerosols. This is where air purifiers can be effective, as they can capture and remove these larger particles along with the attached virus.

For smaller homes or single rooms, a single air purifier may be effective. However, larger, multi-story houses may require multiple machines or a whole-house air purifier connected to your HVAC setup.

Types Of Filtration Explained – How Does An Air Purifier Work?

As we mentioned previously, there are several different air filter types. My air purifier captures, others remove, and still others neutralize contaminants. Most air cleaners will use one or two filtration methods, often combining a capture and neutralizing filtration method.

Let’s take a look at the different possible filtration methods to learn more about them.


A pre-filter is more for the purifier than your air quality. Pre-filters protect the air purifier’s internal components, such as the fan motor, from dust and debris. They capture some contaminants in the air, but their primary purpose is to prolong the life and effectiveness of the other filters. They aren’t dense, usually a sponge material, and won’t capture small particles below about 30 microns.

Activated Carbon Filter

Activated charcoal is a highly effective natural odor absorbent due to its porous structure, which provides a large surface area for adsorption. They are commonly used to capture foul odors, including smoke, fumes, chemical odors, and gases from pollutants known as volatile organic compounds (VOCs). 

However, they may be less effective at capturing larger particles like dust and pet dander. For comprehensive air cleaning, an air purifier with a HEPA air filter and an activated carbon filter is recommended, as it can capture particles and eliminate odors.

HEPA Filter

HEPA (High-Efficiency Particulate Air) filters are widely regarded as the most effective filtration method for removing allergens and improving air quality. HEPA air filters use a dense weave of filter material to capture particles as small as 0.3 microns in size. 

While they only capture particles down to 0.3 microns in size, they may not capture all bacteria or viruses in the air. However, they are still highly effective at removing most airborne particles. HEPA air filters have an effectiveness rating of 99.97%, making them a reliable choice for air purification.

Alternative Filtration Types

Ionizers, UV light, and PlasmaWave are alternative air purification technologies that are not technically filters. They work differently than traditional air filters that physically capture pollutants.

While these technologies can effectively remove certain pollutants from the air, I stick with traditional filters. Alternative filtration types may not be as effective as traditional filters for removing larger particles like dust and pet dander.

Additionally, some people may be sensitive to ozone produced by ionizers and PlasmaWave technology.


Ionizers are not traditional filters that physically capture pollutants. Instead, they use negative ions to attract and neutralize airborne contaminants like allergens, molds, and bacteria. 

There are two main types of air ionizers: external and internal. External ionizers emit negative-charged ions into the air, which attach to particles and cause them to fall to the ground, where they can be cleaned up. Internal ionizers use charged plates or rods to attract pollutants, which then stick to the plates or rods and are removed from the air.

UV Light

UV light is not a filtration type but a purification method that destroys bacteria and some viruses in the air. It does not capture particles or retain dust and debris like traditional filters. Instead, it breaks down the molecules, making them harmless to humans. Like activated carbon, UV light is not very effective on its own, but it can be used with other filtration methods to enhance its effectiveness.

Related Article: Do UV Air Purifiers Work?


PlasmaWave is a patented technology from Winix. It attacks the molecular structure of pollutants, including viruses and bacteria. 

PlasmaWave technology creates a plasma discharge that breaks down water vapor in the air, producing hydroxyls, hydrogen ions, and other reactive components. These reactive components then react with and break down pollutants in the air by disrupting their molecular structure. 

While PlasmaWave technology has been shown to be effective in breaking down pollutants, further research is needed to assess the effectiveness of this technology and any potential health risks.

Currently, this method of filtration is only available in Winix products. However, if it proves viable, it may be adapted to other brands and products.

Filtration At A Glance

In the chart below, we look at all the filtration types to compare them on their filtration abilities.

Filter Type















Activated Carbon










UV light










Benefits Of An Air Purifier

Air purifiers have several benefits and can improve the overall quality of the air inside your home. By removing pollutants such as dust, pet dander, and other allergens, air cleaners can alleviate itchy eyes, runny noses, and headaches that result from poor indoor air quality. My air purifiers are especially helpful for my little guy with asthma.

Air purifiers also help to circulate your air, which can be particularly important in homes with poor ventilation. Improved circulation can keep dust and other pollutants from accumulating on flat surfaces, keeping your home cleaner.

Air purifiers with activated carbon filters can also eliminate unpleasant odors in your home, particularly those caused by pets or cooking.

How To Make Your Air Purifier More Effective

To get the most out of your air purifier, avoid blocking the vents and ensure there’s enough space for air to circulate around the unit. I run into countless people who make the mistake of putting the vents against a wall in the corner.

You should also direct the output airflow into the center of the room and avoid directing it toward walls or floors.

Running the air purifier 24/7 can help maximize its performance, but it may not always be necessary.

Regular cleaning and maintenance are also essential to keep your air purifier working effectively. The effectiveness of air cleaners can also depend on the specific model and the pollutants present in the indoor environment.

When An Air Purifier Won’t Help Your Home

Sometimes an air purifier isn’t enough. For instance, homes with dust build-up should be cleaned before air purifiers can effectively reduce dust levels.

Air purifiers may also struggle to resolve odor problems caused by standing mold, clogged drains, or other odor-producing sources. Even if an air purifier can help reduce the odor, it may not completely eliminate the source of the problem.

Also, if doors and windows remain open, the air purifier may not effectively circulate and replace the contaminated air with cleaner air.

HEPA air purifiers can help capture and reduce the spread of bacteria and viruses in the air. However, it is essential to note that air cleaners alone cannot completely eliminate the risk of infection or transmission. Following other preventive measures, such as regular hand washing, is recommended to minimize the spread of infectious diseases.

What To Look For In An Air Purifier?

To ensure that you are investing in an effective air purifier, it is essential to take into account the following factors before buying an air purifier:

  1. 1
    AHAM verification:
    The Association of Home Appliance Manufacturers (AHAM) sets standards that ensure the safety, efficiency, and performance of various home appliances, including air purifiers. Most reputable air purifiers undergo this voluntary certification program, including a CADR rating and size guidelines.
  2. 2
    Size guidelines:
    It is important to select an air purifier designed for a room larger than the one you plan to use if you wish to operate it in a lower, quieter setting.
  3. 3
    True HEPA air filters:
    These filters effectively eliminate ultra-fine particles like dust mites, dander, pollen, mold, and other common allergens in the home. A true HEPA air filter is required to remove at least 99.97% of particulates that are 0.3 microns in diameter in a lab setting. The effectiveness of these filters is lower in real-life settings as new air pollutants are constantly emerging. Beware of HEPA air purifiers that use marketing ploys such as “HEPA-like” or “HEPA-type,” as these terms are not standardized in the industry.
  4. 4
    CADR (clean-air delivery rate) rating:
    This rating measures the speed at which the purifier can clean the air of smoke, dust mites, and pollen. It is recommended to choose an air purifier with a CADR rating of at least 300. Air purifiers with a CADR rating above 350 are considered to be more effective.

People Also Ask (FAQs)

Can air purifiers prevent coronavirus?

Air purifiers can help minimize the spread of coronavirus by reducing the amount of airborne virus particles, but they cannot completely prevent infection. HVAC filters can also help minimize the spread.

Where should you place an air purifier in your home?

Air purifiers should be placed in a central area with proper circulation. It is best to have a few feet of clearance on all sides. However, air purifiers can be placed in living rooms, bedrooms, or even hallways to help move air and improve indoor air quality.

How long does it take an air purifier to clean a room?

The time it takes for an air purifier to clean a room is typically between 30 minutes and 2 hours. The time it takes depends on several factors, including the room’s size, the air purifier’s CADR rating, and the air pollution level in the room.

Do air purifiers help you sleep better?

Air purifiers can help you sleep better by improving air quality and removing air pollutants and allergens. Clean air leads to better breathing and improved sleep quality for some individuals.


My air purifier has been fantastic and it has really helped improve my indoor air. Once I educate my clients on how they work, they all have a newfound appreciation for what these little (and big) machines can accomplish.

By reducing contaminants and allergens, air purifiers promote fresher and cleaner air, making your home a more comfortable and healthy space. Investing in an air purifier is a great way to ensure long-term health benefits for you and your family.

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Josh Mitchell


Josh Mitchell
My name is Josh and I am obsessed with home appliances. From portable AC units to heaters and air purifiers, I enjoy testing, learning and using these devices to improve the air quality inside my family home.

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Midea U Shaped Window Air Conditioner

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