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What Does an Air Purifier Do?

Last updated March 16, 2023

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Author avatar James Booth

As an experienced content producer and editor, James makes sure our content is always compelling, clear, and useful. He also leads the production team and makes sure our writers have everything they need to keep doing their best work. On his off days, you'll find him outside hiking or searching for stone circles.

Our verdict:

Air purifiers are great for removing ultrafine particulate matter from your environment. They can do this by sucking in the air, passing it through a series of ever-finer filters, then expelling clean air back out.

With the risks of indoor air pollution, removing these from your environment using an air purifier has many health benefits. This is especially true for asthma and allergy sufferers but also for anyone in your home.

Those suffering from the following can benefit greatly (all of which is backed up by science and research):

  • Seasonal allergies
  • Asthma caused by dust mites or pet dander
  • Mold
  • Pollution, smoke (including wildfire smoke) and odors.

If you decide an air purifier is right for you, choose one fitted with activated charcoal and HEPA filters. These are most effective at removing the maximum ultrafine particulate matter from your environment.

If you’ve been wondering what the buzz is with air purifiers, you’ve come to the right place! 

With more and more people worried about indoor air quality, air purifiers have become increasingly popular. This is particularly true in the last few years.

Researchers have even found that adults exposed to poor air quality and pollutants in their early life are more likely to develop severe respiratory issues such as Chronic Obstructive Pulmonary Disease, asthma, allergies and decreased lung function.

But what — you may be wondering — does an air purifier do? Are they effective and should you invest in one for your home or workplace? In this article, we will cover what air purifiers do, how they work and how they can help your health. 

What Does an Air Purifier Do?

Much like the name suggests, air purifiers work to clean your air. They do this by drawing in the air in your environment using fans, passing them through a series of filters and then expelling the cleaned air back out again.

That, in a nutshell, is the entire process. But, of course, it’s a little more complex in reality – so we’re going to break down each stage more comprehensively!

Stage 1: Pre-Filtration

The first stage of your air filter is pre-filtration. The pre-filter has the largest filter and removes larger particles from the air. 

This could include:

  • Dust
  • Hair
  • Pet dander

Pre-filtration allows these larger particles to be removed first, which means that your HEPA filters’ (the filters that remove the finer particles from your environment) performance will be better and last longer.

The pre-filter could be made of various materials such as plastic mesh, material, or a metal grill. Depending on your air purifier, you may be able to either remove it and clean it by hand, replace it (eventually), or simply clean it within the unit.

Stage 2: Activated Carbon Filtration

The next stage in filtration is for your air to pass through an activated carbon filter. Not all devices will be fitted with this filter, but we highly recommend looking for one that is. This is because activated carbon can remove harmful air pollutants, such as Volatile Organic Compounds (VOCs).

VOCs are found in household items, such as cleaning products, aerosol sprays, paint, and more. They have a range of negative health effects, so it’s essential to minimize your contact with them — especially in the air you breathe.

Some harmful VOCs include:

  • Formaldehyde
  • Benzene
  • Naphthalene
  • Chloroform
  • Acetaldehyde.

Activated carbon filters can remove these, as well as other harmful pollutants, in your air. This is because activated carbon filters have been treated with either hot air, steam, or carbon dioxide. This creates a network of minuscule pores inside the carbon, increasing the surface area.

Essentially, the more-porous activated carbon can trap more pollutants in the air (including VOCs and odors) as the air flows through the air purifier device. Clean air then passes out of it.

Odors that your activated carbon filter can remove include:

🍳 Cooking smells and smoke

🚬 Tobacco or weed smoke

💩 Bathroom odors

🐕 Pet odors

However, while carbon filters are excellent at removing these, they cannot remove some smaller ultrafine particles, such as mold, pollen and bacteria. This is where the next stage in filtration comes in!

Pro tip: Check out our detailed post on how activated carbon filters work for a detailed breakdown.

Stage 3: HEPA Filtration

Finally, the last stage in air filtration is High-Performance Particle Air (HEPA) filters. These are the finest level of filter that your air passes through and, arguably, the most important. There are three different types of HEPA filter your purifier may be fitted with, but all of these are made up of fiberglass strands woven together tightly. 

This forms a labyrinth that particles must pass through to be expelled back into your environment. Because the fiberglass strands are “sticky”, any ultrafine particles can become trapped against them — even particles as tiny as 0.3 microns.

📄 This study from 2020 published in Environmental International proved that HEPA purifiers were able to remove ultrafine particulate matter from the environment efficiently and could do so at a similar rate to the standards set by the Association of Home Appliance Manufacturers.

The different types of HEPA filters are:

  • Classic HEPA (able to remove 99% of particles)
  • True HEPA (able to remove 99.97% of particles)
  • Medical-Grade HEPA (able to remove 99.995% of particles).

While the other filters will have already removed larger particles by the time the air reaches the HEPA filter, they can remove even smaller pollutants. 

This includes:

🦠 Bacteria and viruses

🍄 Mold spores

🌺 Pollen

🌫️ Smoke particles

Pro tip: Check out our detailed post on how air purifiers work for more detail about every stage.

What Air Purifiers Can Do For Your Health

So now you know how air purifiers work, let’s talk about how they affect your health. 

Air Purifiers VS. Seasonal Allergies

If you suffer from seasonal allergies — also known as seasonal allergic rhinitis — then you’ll know all too well how they can affect you. According to the Asthma and Allergy Foundation of America, sufferers often complain of:

  • A runny or stuffy nose
  • Sneezing
  • An itchy nose, ears, eyes, or mouth
  • Red, watery, or swollen eyes.

According to this 2018 study in the Asian Pacific Journal of Allergy and Immunology, HEPA air filters significantly reduced both particulate matter and high-density matter allergen concentrations. This greatly improved the effects of allergic rhinitis in the 32 clinical subjects who took part.

This was also backed up by this 2020 study in the Yonsei Medical Journal, where researchers found that air filters could reduce high-density, matter-induced allergic rhinitis.

📄 Air purifiers are so good at removing allergy triggers from the home that this 2014 study in the Journal of Asthma recommended that all households with allergy sufferers should install a high-performing air filter home ventilation system!

Air Purifiers VS. Dust and Asthma

Dust and, more specifically, dust mites and their feces are a huge issue for people living with asthma. In fact, according to this 2016 article in The American Academy of Pediatrics, allergens and pollutants are a huge contributor to premature death in children caused by asthma.

One of their recommended intervention methods was using HEPA-fitted air purifiers in the home, which could positively affect the asthma-related morbidity rate.

However, this 2018 study in the Journal of Allergy and Clinical Immunology also found that using multiple home measures was important to manage indoor allergen-induced asthma effectively.

📄 As shown in this study in the European Respiratory Journal, the recommendation for people living with asthma was to combine air purifiers, and hypo-allergenic mattress covers even as far back as 1997. Doing so reduced the amount of histamine produced in the body and a significant amount of dust and dust mite allergens were caught in the filters.

And, if you were still unsure: this 2020 article from the Yonsei Medical Journal showed that air purifiers could benefit children with asthma by significantly reducing particulate matter levels in the home. 

Air Purifiers VS. Mold

Mold in the home can be unsightly and have severe health repercussions, as this 2005 study in the Annals of Allergy, Asthma, and Immunology showed.

The EPA lists various mold-related health problems, including allergic reactions and asthma. The CDC also notes that severe reactions to mold can include shortness of breath or fever.

📄 However, this study from 2018 published in Biocontrol Science concluded that HEPA-fitted air purifiers could significantly remove fungi and mold from home.

Air Purifiers VS. Pet Dander

Pet dander — the dead skin that comes off your pets (yuck!) can be a huge issue for allergy sufferers. The EPA notes that pet dander is one of a range of biological pollutants in your home that may affect indoor air quality.

Luckily, air purifiers are very effective at removing pet dander from your home — thereby reducing allergy or asthma-related problems caused by pets.

📄 This 1999 study published in Allergy found that HEPA air filters could reduce airborne dog allergens in your environment. 

Additionally, this 1999 study in the Journal of Allergy and Clinical Immunology found that air purifiers could positively affect breathing in young people living with asthma who had pets in the home

Air Purifiers VS. Odors, Pollution and Smoke (Including Wildfire Smoke)

Odors, pollution and smoke (including wildfire smoke) are all particulate matter that you could breathe in, adversely affecting your health or affecting you in other ways. Pollution and smoke can lead to heart attacks or strokes (amongst other issues), according to the American Heart Association.

Specifically, wildfire smoke can affect children and cause respiratory issues or exacerbate existing allergies, asthma and other chronic health issues.

📄 This study from 2021 published in Heliyon showed that HEPA air purifiers were very efficient at removing indoor air pollutants, especially small-sized particles.

This 2022 article from Environmental Monitoring and Assessment also showed that air purifiers could effectively lower ultrafine particulate matter in smokers’ homes and significantly reduce carcinogenic exposure risks.

Researchers who wrote this 2021 study in the Journal of Hazardous Materials specifically found that air purifiers were efficient at removing ultra-fine particulate matter caused by pollution and cost-efficient.

Further Reading: Check out our 6 Science-Backed Benefits of Air Purifiers for more on this topic!

Final Thoughts

As you can see, there are so many benefits to why you should invest in an air purifier.

They are useful devices essential in any home or workplace if you’re concerned about indoor air quality. Additionally, ensuring clean air is one of the key takeaways for healthy living, according to the EPA.

Convinced? If you’re looking for recommendations for air purifiers, be sure to check out some of our air purifier reviews and our lists of best air purifiers available on the market to help you decide.


Asthma and Allergy Foundation of America. (2015). Allergies.

Asthma and Allergy Foundation of America. (2022). Pollen Allergy.

Biocontrol Science. (2018). Effectiveness of Airborne Fungi Removal by using a HEPA Air Purifier Fan in Houses.

Brown, K at al. (2014). Reducing patients’ exposures to asthma and allergy triggers in their homes: an evaluation of effectiveness of grades of forced air ventilation filters.

Centers for Disease Control and Prevention. (2022). Basic Facts about Mold and Dampness.

Dubey, S. (2021). Assessing effectiveness of air purifiers (HEPA) for controlling indoor particulate pollution.

Fazlzadeh, M. et al. (2022). Effect of portable air purifier on indoor air quality: reduced exposure to particulate matter and health risk assessment. 

Green, R. et al. (1999). The effect of air filtration on airborne dog allergen.

Heide, V.D S. et al. (1997). Allergen reduction measures in houses of allergic asthmatic patients: effects of air-cleaners and allergen-impermeable mattress covers.

Heide, V.D S. et al. (1999). Clinical effects of air cleaners in homes of asthmatic children sensitized to pet allergens.

Leas, B.F et al. (2014). Effectiveness of indoor allergen reduction in asthma management: A systematic review.

Lee, G.H et al. (2020). Effects of Indoor Air Purifiers on Children with Asthma.

Liu, Y. et al. (2021). Health benefits and cost of using air purifiers to reduce exposure to ambient fine particulate pollution in China.

Lowther, S.D et al. (2020). How efficiently can HEPA purifiers remove priority fine and ultrafine particles from indoor air?

Luo Jia-Ying et al. (2018). Efficacy of air purifier therapy in allergic rhinitis.

Matsui, E et al. (2016). Indoor Environmental Control Practices and Asthma Management.

Mocelin, H.T. (2022). Adverse early-life environmental exposures and their repercussions on adult respiratory health.

Park, K.H et al. (2020). Effects of Air Purifiers on Patients with Allergic Rhinitis: a Multicenter, Randomized, Double-Blind, and Placebo-Controlled Study.

Portnoy, J.M et al. (2005). Health effects of indoor fungi.

United States Environmental Protection Agency. (2022). Air Cleaners and Air Filters in the Home.

United States Environmental Protection Agency. (2022). Biological Pollutants’ Impact on Indoor Air Quality.

United States Environmental Protection Agency. (2015). Heart Disease, Stroke, and Outdoor Air Pollution.

United States Environmental Protection Agency. (2022). Mold and Health.

United States Environmental Protection Agency. (2023). Protecting Children from Wildfire Smoke and Ash.

United States Environmental Protection Agency. (2022). Volatile Organic Compounds’ Impact on Indoor Air Quality.

United States Environmental Protection Agency. (2022). What are volatile organic compounds (VOCs)?

United States Environmental Protection Agency. (2022). What is a HEPA Filter?