What Is A HEPA Air Purifier?- The Most Important Knowledge About a HEPA Air Purifier

“HEPA”, “HEPA-type”, “True HEPA”, “HEPA technology”, etc. We bet that none of us here haven’t seen or heard about these when we look for an air purifier to buy.

So, what is a HEPA air purifier? How does it work? Should you use it? Is there any note about purchasing and using it?

Well, we seem to have numerous questions about this equipment before buying an air purifier. That’s why we wrote this article and now give it to you as a gift.

Let’s check it out!

HEPA air purifier
Are you curious about what a HEPA air purifier is and how it works? 

What Is A Hepa Air Purifier?

HEPA stands for high-efficiency particulate air. As such, a HEPA filter air purifier is a high-efficiency particulate air purifier.

A True High-efficiency particulate air purifier cleans the air by using a mechanical filter that can capture air pollutants down to 0.3 microns in size (e.g., mold dust, pollen dust, dust smoke, dust mites, etc.) at an efficiency rate of 99.97%.

Yet, several HEPA air purifying machines may use HEPA filters at different quality.

For instance, a premium HyperHEPA filter in IQAir air purifiers has a 99.99% efficiency of trapping 0.003-micron particles (100 times smaller), while Coway Airmega and Austin Air models merely use standard True HEPA filters above.

Besides, there are HEPA-type and HEPA-like filters that only work against airborne particles at the size of 2 microns.

The effectiveness of air filters is measured in MERV (Minimum Efficiency Reporting Value), and a True HEPA filter is around 17-20 MERV.

What is a HEPA filter made of?

A standard HEPA filter is crafted from countless thin and fine fibers in high density so that microparticles like dust mites, mold, pet dander, bacteria, germs, and viruses cannot get through.

Materials used to make a HEPA filter are often borosilicate glass or plastics like polypropylene since they are easily melted and reshaped into a mesh. Perhaps you cannot imagine, but a HEPA filter that is 2.5 mm (or 0.10 inch) in width can be made from 2.500 layers of glass threads.

With around 5% acrylic binder (the compound used to bind latex paint to the walls), manufacturers bind and compress these glass threads together to create a filter mat. Due to the microscopic size of separate threads, the majority of the mat comprises air.

The holes on the mat are extremely small, typically smaller than 0.5 microns (equal to 0.0005 mm or 0.00002 inches). However, they are still able to capture particles as small as 0.3 microns (0.0003 mm or 0.00001 inches) in diameter.

The glass threads used to produce a HEPA air filter are often smaller than 1 micron (equal to 0.001 mm or 0.00004 inches) in diameter. To compare, a human hair is approximately 75 microns (0.07 mm or 0.003 inches) in diameter.

How do HEPA Filters Work?

HEPA filters
The filtration mechanisms of HEPA filters

You might think a HEPA filter works just like a filter media, but it is not so simple. In brief, you can look at the above picture that shows the four ways in which a HEPA filtration system purifies the air.

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To specify, a True HEPA air purifier might use up to four air cleaning methods at the same time to improve the air quality in your home, including:

  • Diffusion: Smallest particles will collide with ambient gas molecules, hence cannot get through the filter.
  • Interception: Big particles run into and are stopped by the fibers directly
  • Inertial impaction: Particles will adhere to fibers that are close to them
  • Electrostatic attraction: The filter may be charged with negative ions to attract positive ions of pollutants.

Advantages and disadvantages of a HEPA air purifier?


  • A HEPA air purifier uses powerful fans to pull the air around and get filters to remove airborne particles. Therefore, they can cover a wide area of up to nearly 2000 sq ft while others typically sanitize your indoor air within a room.
  • If you want to alleviate allergies, you can rely on a HEPA filter for allergies.

They improve your indoor air quality by using a particulate arresting method that is effective against dust dander pollen, pollen mold, dander pollen, dust mold, and other factors causing allergy and asthma.

HEPA filters are the best filters for allergies.

  • It does not emit ozone like an ozone generator or pose any other potential risks for human health.
  • HEPA filters can be combined with other technologies such as Ultraviolet lights, ionizers, etc.


  • A True HEPA filter only traps instead of destroying viruses, germs, and bacteria without a UV light. This may lead to mold growth on your HEPA filter if you do not clean mold spores, dust dander trapped on it regularly.
  • A High-efficiency particulate air purifier is not good at removing smoke or getting rid of pet odors, volatile organic compounds without carbon filters.

To eliminate odors, odors smoke, or odor smoke dust, a model must include extra activated carbon filters with the activated carbon components.

  • The replacement filter may cost you quite a lot in the long run. You will have to change new filters every month to maintain the device’s performance.


A HEPA air purifier is still a good choice to filter air and enhance your home air quality because its benefits outweigh its drawbacks.

Moreover, if you buy a HEPA air purifier with additional activated carbon filters and UV lights, they will no longer have any disadvantages except for the high expense.

Who uses a HEPA air purifier?

HEPA air purifier
Finding groups of people who need HEPA air purifiers will help you a lot.

Normally, if the level of contaminants and odors like dust dander, dust pollen mold, or smoke dust in your house is low, you can purchase air cleaners, or even an air conditioner can remove odors and remove particles at a certain level.

Nevertheless, if the problems you have to face are more serious, you should use a HEPA air purifier. But if you might not even realize these invisible issues, we will list some groups of people that often need a HEPA air purifier for you to consult. These people include:

  • Those in hospitals, laboratories.
  • Workers in factories.
  • Babies and older people.
  • People who are suffering from respiratory issues.
  • Those who live in the city center, especially near the crowded roads and construction sites.
  • People participate in activities in restaurants, bars, hotels, commercial centers, and other indoor public places.
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How long does a HEPA filter last?

This is the air purifier FAQ that receives the most concern from consumers, but it may have several different answers.

Depending on the indoor air quality, type of air purifier the filter is installed in, other filters in the filter system, your HEPA filter may last from a half to even ten years.

For example, if the model you are using provides a prefilter to trap larger particles before they reach the True HEPA filter, and the indoor air quality is medium, a HEPA air filter can last for around two years before you need to replace them.

If you use your a HEPA filter air purifier to handle extreme indoor air pollution without the help of other filters, you should change HEPA filters within 6 months to ensure the air filtration capacity of your devices.

This might never happen, but we can use another funny example. Assumed that your True HEPA air purifier is used in a Manhattan Project, its filtration system would be broken down by radioactive particles in seconds!

Are HEPA filters washable?

There are several types of HEPA filters, but only one of them is washable while the rest is not.

Except for permanent HEPA filters, no other HEPA filter should be washed. These permanent HEPA filters are specially designed to endure water so that they can be washed again and again to be used for many years.

Meanwhile, to clean non-washable HEPA air filters, you can only vacuum them.

What is the difference between HEPA and HEPA-type filters?

The most significant difference between a True HEPA and a HEPA-type filter is their filtration performance (the particle size that they can trap).

In particular, a HEPA-type filter captures particles at the size of 2 microns (e.g., pet dander, human hair) at an efficiency rate of 99%. Meanwhile, a True HEPA filter offers a 99.97% efficiency rate of trapping particulate air pollutants down to 0.3 microns in size (e.g., dust pollen).

As such, they use the same air purifier technology, but a HEPA-type filter structure is not as dense as a True HEPA filter.


Now you know what is a HEPA air purifier, what HEPA standards are, whether you should buy an air purifier using a HEPA air filter or not, as well as much other essential information about this type of filter.

Hopefully, you can make the right decision after this article. Thanks for reading!

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