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What Does an Air Purifier Do?

Last updated November 7, 2022

This post may contain affiliate links.

Author avatar Danny Ashton

Danny as been writing about air purifiers for 10+ years. He is a major fan of home technology, which makes him the perfect person to test and evaluate products for HouseFresh

Just as we need to breathe to live, so do we need clean air to thrive. Unfortunately, the air we breathe is not always as clean as it could be – especially in large cities. This is where air purifiers come in, helping to clean the air we inhale.

As experts in the field, many readers ask us “what does an air purifier actually do?” among many other inquiries. 

So for the beginners, we’d like to take this opportunity to answer some of these questions and provide further information about air purifiers. 

We’ll discuss what air purifiers do, how they work, and their benefits. And while we’re at it, we’ll dispel some myths about air purifiers.

What Does an Air Purifier Do?

Air purifiers work to clean the air by using a combination of filters and a fan. The filters trap particles like dust, pollen, and smoke, while the fan circulates the air in the room. This helps to improve air quality and reduce allergens. Some purifiers can also get rid of gases and odors from the air.

Air purifiers come in all shapes and sizes and with various features. But do you know how they work? 

Let’s break down the four main stages through which an air purifier cleans the air.

Stage 1: Pre-filtration

The pre-filter is typically a pleated filter that is easy to replace. It is the first step in the purification process. 

🤔 What does this step do? 

The pre-filter removes large particles from the air, such as:

  • Dust
  • Hair
  • Pet dander
Maintenance Tip: It is important to clean the pre-filter regularly, as it becomes clogged with dirt and debris over time.

Stage 2: Activated Carbon Filtration

This filter uses a type of carbon that has been treated to make it more porous. This allows it to adsorb more pollutants from the air. 

🤔 What does this step do? 

The activated carbon filter is effective at removing volatile organic compounds (VOCs) and odors. 

Here’s what the process looks like:

  1. Contaminated air enters the filtration system
  2. The air passes through the activated carbon air filter
  3. Contaminants stick to the outside of the carbon
  4. Purified air flows out of the activated carbon filter and back into the room

🤔 What does an activated carbon filter remove?

The activated carbon filter removes odors from:

  • Cooking
  • Cigarette smoke
  • Bathroom
  • Pets
  • Weed smoke

It also removes Volatile Organic Compounds (VOCs) such as:

  • Formaldehyde
  • Benzene
  • Naphthalene
  • Chloroform
  • Acetaldehyde

Be sure to check out our detailed write-up on activated carbon for more information. 

Buying Tip: The general rule when looking for a decent activated carbon filter for an air purifier is the more carbon it contains, the more efficient the filter will be.

Stage 3: HEPA Filtration

HEPA filters (High-Performance Particle Air) are a mat of randomly arranged woven fibers. They form a maze of sorts, which have allow airflow but trap particles as they try to pass through. 

To put it simply, they filter minuscule pollutants from the air. 

There are three types of HEPA filters:

  • Classic HEPA — 99% of particles removed
  • True HEPA — 99.97% of particles removed
  • Medical-Grade HEPA — 99.995% of particles removed

🤔 What does this step do? 

The HEPA filter removes tiny common household airborne particles that can harm our health, including:

  • Bacteria
  • Viruses 
  • Mold
  • Pollen
  • Smoke
Buying Tip: It’s worth doing a bit of reading to help you decide which kind of HEPA filter is right for you before taking the plunge.To help, check out our guide here.

Should I Buy an Air Purifier?

The simple answer is, yes. 

Air purifiers have a wide range of uses, which benefits the occupants of a room greatly. They can improve air quality, which is especially important if you suffer from allergies or asthma. Air purifiers can also help reduce the amount of pet dander in your home and eliminate unpleasant odors.

You don’t have to take our word for it, though. Here are five scientific facts and stats that back up our claims. 

Air purifiers can reduce the amount of pollen in the air by up to 60%The Journal of BMC Public Health. 

An air purifier can help remove smoke particles from the air and improve your healthThe Centers for Disease Control and Prevention.

An air purifier can help reduce exposure to mold spores and improve indoor air quality — The Centers for Disease Control and Prevention. 

For people with asthma, an air purifier can help improve their breathing by removing allergens and other particles from the air —  Allergo Journal International

People with allergies who used an air purifier had reduced symptoms and improved quality of life — National Library of Medicine  

More scientific evidence of the benefits of having an air purifier can be found here

The Questions We Get Asked The Most

As industry experts we get our fair share of questions from consumers who are looking to buy an air purifier but don’t know where to start. Below we’ve compiled the questions we get asked the most and provided clear answers for each one. 

🙋 Do air purifiers actually work?

Yes, but the type and size of the purifier matter. 

🤓Research Findings 📋

According to a study published in the journal Environmental Science & Technology, small air purifiers can remove up to 82% of airborne particulate matter, while large ones can remove up to 98%. 

However, the study also found that the type of filter used made a big difference; filters with high arrestance rates were more effective than those with lower arrestance rates.

🙋 Will an air purifier help my allergies?

Yes, there is some scientific evidence that air purifiers can help people with allergies.

🤓Research Findings 📋

A study published in the journal CHEST found that air purifiers can help reduce the symptoms of allergies, such as sneezing and a runny nose. The study found that air purifiers were especially effective at reducing asthma symptoms.

For more info, we’ve researched and written about the different causes of allergies and respiratory conditions, including pet dander, dust mites, and asthma. We also looked at whether air purifiers can make allergies worse

🙋 Should I sleep with the air purifier on?

Yes, air purifiers can help improve sleep quality by removing allergens, dust, and smoke from the air. They can also help reduce the time it takes you to fall asleep and improve your overall sleep efficiency.

Important: If the filter is not replaced regularly, it can release harmful pollutants into the air. Additionally, if the machine is not correctly sized for your room, it can create negative pressure and increase the amount of dust and pollen in the air.

🙋 How effective are home air purifiers?

Research suggests that home air purifiers can effectively reduce levels of particulate matter in the home, but there is significant variability among different models.

🤓Research Findings 📋

A recent study published in the Environmental Science and Technology found that, on average, air purifiers could reduce levels of particulate matter by about 50%. However, there was significant variability among different models of air purifiers. The study also found that an air purifier’s effectiveness decreased as the particulate matter’s size decreased.

🙋 How do air purifiers work?

Air purifiers come in various shapes and sizes, but all work to improve the air quality in your home. They work by trapping particles in the air and then releasing them back into the environment when they are full. This process occurs over and over again, trapping more and more particles until the air purifier is either turned off or it runs out of filter material.

Important: All air purifiers should be certified by the Association of Home Appliance Manufacturers (AHAM) to ensure they meet safety standards.

🙋 How long should you run an air purifier a day?

The time you should run your air purifier each day depends on various factors, including the type of air purifier you have and the size of the room. In general, however, it is recommended that you run your air purifier for at least two hours per day. This will help remove pollutants from the air and improve indoor air quality.

🤓Research Findings 📋

A study published in the Journal of ScienceDirect found that running an air purifier for two hours per day reduces levels of particulate matter in the air by up to 50%. Particulate matter can cause respiratory problems, so reducing levels of this pollutant is important for your health.

🙋 How much does it cost to run an air purifier? 

The cost of running an air purifier will vary depending on the type and size of the unit. However, according to the U.S. Department of Energy, most air purifiers use about 60 watts of electricity per hour, which is about the same as a light bulb. So, running an air purifier for eight hours per day would cost about 48 cents per day (based on the national average cost of electricity).

The specific costs of running an air purifier will also vary depending on the electricity rates in your area. In general, running an air purifier costs between $0.50 and $1 per day, which is a relatively low cost compared to the health benefits of using an air purifier. 

🙋 What is a filter? 

A filter is a device that removes unwanted particles from the air. These particles can be anything from dust and pollen to smoke and bacteria. Filters are often used in air purifiers, machines that clean the air inside a home or office.

There are many filters, but they all have one purpose: to remove something from the air. Air purifiers use filters to remove pollutants from the air in your home. Different filters are effective at removing different types of pollutants. Some filters remove particles, while others remove gasses and odors.

Some filters are made of natural materials, like activated carbon, which is effective at removing gasses and odors. Other filters are made of synthetic materials, like polypropylene or fiberglass. These filters are effective at removing particles from the air.

The effectiveness of a filter depends on its size, density, and airflow rate. The size of a filter determines how much air it can cleanse in a given period. The density of a filter determines how many particles it can capture before clogging.

🙋 Do air purifiers weaken the immune system?

There is no concrete evidence to support this claim. 

🤓Research Findings 📋

A study published in the journal NCBI found that air purifiers do not remove enough air bacteria to significantly impact human health. The study looked at three different types of air purifiers and found that none of them was able to reduce bacterial counts by more than 50%.

Another study looked at whether air purifiers could increase rates of asthma and allergies. The study found no link between using an air purifier and developing asthma or allergies.

Final Thoughts

Now that you know what an air purifier is and how it works, it’s up to you to decide which one works best for you. Before settling on an air purifier, consider factors such as costs, the type of filter, and the size of your room. 


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