What is a HEPA filter and how does it work?

A HEPA filter is a type of air filter that removes at least 99.97% of the particles in the air from 0.3 microns to 10 microns which are commonly known as allergens, dust, mold spores, pollens, and other irritants. These filters can be found in many homes or offices to help people with allergies or respiratory conditions breathe easier by managing indoor air quality better.

It’s important to note that not all filters labeled “HEPA” are actually true HEPA filters, so it’s best to purchase one made by an established company you trust for your family’s health and safety!

This blog post will discuss what a HEPA filter is and how they work. We’ll also touch on some common misconceptions about these filters and how they work in order to help you better understand if they are right for your home or office.


What is a HEPA filter?

A high-efficiency particulate arresting filter (HEPA) is a type of air filter that removes 99.97% of the particles from the air 0.3 microns to 10 microns in size. This includes allergens, dust, mold spores, pollens, and other irritants.

What Does HEPA Mean?

HEPA stands for high-efficiency particulate air filters, often found in the home and office air conditioner/heating systems to help circulate clean, filtered air inside a house or business. These filters are capable of removing 99 % of all particles that are 0.3 microns and larger in size from the air. This includes common allergens, dust, mold spores, pollens, and other irritants, which can often cause respiratory problems for people with allergies or sensitivities.

How Does a HEPA Filter Work?

A HEPA filter works by forcing the air through a series of filters, screens, and/or fibres that remove or trap microscopic particles in the air. These filters are complex to create, so it’s important you buy your HEPA filter from a name brand company you trust, which can ensure quality control and effectiveness within these devices.

There are several ways HEPA filters work to capture particles from the air, but the three most common methods are diffusion, interception, and impaction.

 Tiny Particles: 

Diffusion– This is one of the oldest and most common methods of HEPA filtration. In this method, tiny particles that are airborne, such as dust, pollens, mold spores, and allergens, are pushed through the filter by the passing air, causing them to be captured on the filter medium, which may include a number of different materials. If the particle is large enough or has a large enough surface area, it may not be able to pass through the filter.

Medium-Sized Particles: 

Interception– The second HEPA filtration method works best to remove medium-sized particles like pollen, dander, dust mites, and other allergens. This type of HEPA filter includes a collection bag or container attached to the top of the device. As the air passes through the filter, the airborne particles become trapped in the collection container. As the collection container becomes filled up with these particles, the pressure within the unit increases. This causes a door or flap in the front of the filter to open and release the collection container so you can remove and replace it when it is full.

If the particle is too large or has a large enough surface area to make it past the filter, it will be too large to be captured by the collection container and will simply fall through the unit and out the bottom.

Large Particles: 

Impaction– The third and most effective method of HEPA filtration works best for removing large particles such as smoke, pollen, dust, and other irritants. This type of HEPA filter uses a specially-designed material called a “precoat” on the inside of the filter. As the air passes through the filter, the airborne particles become trapped on the precoat material.

This type of HEPA filter also has a very high-pressure drop across the filter, which means less air flows through the filter. This makes it more efficient at removing larger particles from the air.

If the particle is too large or has a large enough surface area to pass through the filter, it will be too large to be captured by the precoat material and will simply fall through the filter and out the bottom.


Different Types of HEPA Filters:

HEPA filters are used in both commercial and residential applications, but they can also be used in other industrial applications, such as manufacturing, warehousing, and food processing plants.

In addition, they can be used in a number of different environments, including schools, offices, restaurants, hospitals, hotels, and healthcare facilities. They can also be used in a number of different applications, including dryer vents, HVAC systems, home air purification units, commercial air cleaners, air scrubbers, and more.

In general, there are three types of HEPA filters: bag-style, plate-style, and pleated.


Bag-Style HEPA Filters:

Bag-style HEPA filters are by far the most popular type of HEPA filter in use today. They are made out of a synthetic material called polypropylene and have an average efficiency rating of 95% or better.

Bag-style HEPA filters come in a variety of sizes and are available with or without an integral bypass mechanism. Without a bypass mechanism, when the collection container becomes full, you should remove and replace it as described above. When the collection container becomes full, you should remove and replace it with a bypass mechanism, but the filter will continue to operate until it is completely clogged.

Plate-style HEPA Filters:

Plate-style HEPA filters are much less common than bag-style HEPA filters. They are also made out of polypropylene and have an average efficiency rating of 90% or better. The plates in these filters are usually made from aluminum, but they can also be made of other materials such as stainless steel, carbon fiber, or ceramic.

Plate-style HEPA filters are also available with or without an integral bypass mechanism. Pleated HEPA Filters: Pleated HEPA filters are the most efficient and reliable type of HEPA filter available today.

Pleated HEPA Filters:

Pleated HEPA filters use a very thin, high-quality material called a “pleat” to create a very high filtration area for a very low-pressure drop. These filters are by far the most efficient and reliable type of HEPA filter available today. However, they are also the most expensive filters to manufacture. They can only be used in applications where the airflow rate is extremely low (less than.1 cfm) and should not be used in environments with higher airflow rates, or else the pleats will be damaged or destroyed.


What Makes a Filter a HEPA Filter?

A HEPA filter must meet certain standards in order to be called a HEPA filter. A HEPA filter must remove 99.95% of particles in the European Union. In the United States, it must remove 99.97% of particles. To be called a ULPA filter, it must remove 99.999% of particles. The American standard (MIL-STD-282) is very similar to the European standard (ISO 29463).

A HEPA filter goes through rigorous testing to ensure that it gets rid of 99.97% of particles 0.3 micrometers in size, 90% or more of particles 1 micrometer in size, and at least 80% of particles between 1 and 10 micrometers in size. Standard air filters, which do not use a HEPA filter, only go through testing on the 0.3 micrometer-sized particles because those are most likely to enter your lungs once inhaled.

To be considered “ultra-low penetration,” or ULPA, a filter must remove 99.999% of all particles, including those as small as 0.1 micrometers.

HEPA filters can also be called “high-efficiency particulate air filters” or “EPA filters.” Filters that capture between 85% and 99.95% of particles are called EPA filters, while filters that capture more than 99.95% of particles are called HEPA filters.

HEPA stands for the high-efficiency particulate air filter. The acronym was coined by the U.S. Atomic Energy Commission in the late 1940s to describe a very efficient air-cleaning device originally made for use in its nuclear facilities. The commission’s criteria for a HEPA filter were that it must remove at least 99.7% of all particles from the air, including dust, pollen, smoke, and other solid or liquid pollutants.

The original HEPA filters met the commission’s tough requirements by capturing 99.97% of all particles down to 0.3 micrometers in size. Today’s HEPA filters still meet that standard and can also remove particles as small as 0.1 micrometers.

While there are no official government or industry standards for the term “HEPA filter,” most filters marketed as such must meet stringent performance ratings set by organizations such as the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) or the European Committee for Standardization (CEN).

Many “HEPA” air filters are actually at least 99.5% effective in removing particles 0.3 micrometers and larger, but they may not meet the more demanding requirements of HEPA standards to remove smaller particles as well.


What’s the smallest particle size that a HEPA air filter can capture?

The answer to this question is a little trickier because it depends on the filter. Some filters can capture particles as small as 0.1 microns, while others can only capture particles down to 0.3 microns.

As we mentioned earlier, the most penetrating particle size is the size of particle that a HEPA air filter is the least effective in capturing. This is because diffusion is most effective under about 0.3 microns, and straining is most effective above 0.3 microns.

The size of the smallest particle that a HEPA filter can trap depends on the size of the MPPS. The MPPS is the size of particle that a HEPA air filter is the least effective in capturing. This can depend on a number of factors, such as air pressure and airflow rate, so it’s difficult to give an exact answer to this question without knowing all of these factors.

The most important thing to remember is that a HEPA filter with a larger particle size will be able to capture more particles–including smaller particles–than a HEPA filter with smaller particle sizes. So it’s important to pick the best HEPA filter depending on your requirements.


The Difference Between True and HEPA-Type Filters

When looking for a HEPA filter, it’s important to know the difference between true and HEPA-type filters.

True HEPA filters are certified to meet specific performance ratings at a size of 0.3 microns. All particles down to 0.3 microns are captured with a 99.97% efficiency or higher.

HEPA-type filters are marketed as HEPA filters because they have the ability to capture particles 0.3 microns and larger, but they may not meet true HEPA standards for capturing smaller particles.

When choosing an air filter for allergy sufferers or other sensitive individuals, the difference between true HEPA and HEPA-type filters is important to understand. HEPA-type filters are not certified to capture the smallest particles, which means they may still harbor bacteria and mold spores.

It is best to choose a true HEPA filter when wanting to remove dust mites from your home while also being able to reduce allergy symptoms. For example, if you have allergies but do not want a sealed system, a true HEPA filter may be the best option. If you are looking for a vacuum with a sealed system, then you will need to find a vacuum that is specifically labeled as “true HEPA.”

HEPA-Type Filter – Dust particles as small as 0.3 microns (0.00001 inches) are captured by the filter, such as pollen and dust mites, pet dander, and mold spores; however, not all particles that cause respiratory issues will be caught in a HEPA-type filter.

True HEPA Filter – A certified True HEPA filter is able to trap particles in the range of 0.3 microns with a 99.97% efficiency or better. These filters are able to remove tiny particles such as mold spores, pet dander, smoke, and bacteria from the air.

The size of the MPPS also depends on the type of filter. For example, a pleated filter with a high MPPS will have more surface area to capture particles than a non-pleated filter.

When picking a filter, it is necessary to assess the size of the particles that will be captured. Many filters claim to capture small particles, but only true HEPA filters are certified to do so. True HEPA filters have a higher minimum particulate-penetrability specification (MPPS) than other types of filters. This means that they are able to capture a higher percentage of particles as small as 0.3 microns.

Most filters sold in home improvement stores are not true HEPA filters and will not meet the standard for capturing small particles. However, some filters marketed as HEPA-type filters may perform similarly to a true HEPA filter. It is important to read the filter specifications before purchasing to be sure you are getting the level of filtration you need.

HEPA filters are an important part of keeping your home healthy by removing allergens and other particles from the air. Be sure to understand the differences between true HEPA and HEPA-type filters before making one purchase.

True HEPA filters are certified to capture particles as small as 0.3 microns with a 99.97% efficiency or higher, while HEPA-type filters may not meet these same standards. When considering a type of filter, remember to figure out the scale you need to catch and what you are trying to capture. Filters that claim to capture small particles must be true HEPA filters to do so.

Do you Really Need a HEPA Filter?

It’s important to note that while many health problems are caused by the presence of allergens, dust, mold spores, or pollutants in the air, not all can be solved with a HEPA filter alone. For example, while you might find relief from these particles in your home.

Should I buy a HEPA air purifier for my home?

Yes, if you want to capture large particles (dust, pollen) and do not mind the drawbacks of high-pressure drops, limited surface area for filter media, recirculation issues, etc.

No, if you are concerned about particles sized in the submicron range that HEPA does not address, such as VOCs, viruses, and bacteria.

When is a HEPA Filter Important? 

There are many reasons for using air filters in an indoor environment. They can be used to clean the air of common particles that may cause asthma or allergies, or they can simply be used to reduce odors and improve the quality of the air we breathe. Of course, there is a big difference between types of filters and their ability to do their job.

A HEPA filter is a good method of cleaning the air in your house or office. It removes many harmful particles from the atmosphere, making them easier to breathe and less dangerous for you and others nearby. HEPA filters are designed to remove up to 99.97% of all particles from the air that passes through them, down to a size of 0.3 microns. This makes them ideal for filtering the air in indoor environments such as greenhouses, laboratories, and hospitals.

A large number of people who suffer from asthma or allergies may also need to employ HEPA filters in their own homes if they want to avoid symptoms. Replacing a standard filter with a HEPA filter can make all the difference between having symptoms and not having them. In fact, many experts believe that HEPA filters are the only type of filter that should be used in the home if someone wants to improve their indoor air quality.

HEPA filters can also help you eliminate bad smells from your house by trapping the air and removing any particles or dirt that might have settled on them. Pets, cooking, and smoking can all cause unpleasant smells in a home. Installing a HEPA filter in the ventilation system can help to remove these smells and make the home more pleasant to live in.

Where do HEPA air filters fail?

HEPA filters are not perfect and can still allow some particles through. In particular, they can be ineffective at trapping very small particles, often called nanoparticles. These tiny particles can be especially harmful to your health as they can penetrate deep into your lungs.

Some studies have shown that HEPA air filters can actually increase the number of nanoparticles in the air. This is because the filters can trap larger particles, which then break down into smaller ones. These smaller nanoparticles can be more dangerous than the original larger particles.

HEPA air filters also have a limited life span. Once they are clogged with dust and other particles, they stop working effectively. This means that they have to be replaced regularly.

Finally, HEPA filters may not reduce VOCs very well, even though they are designed to do so. Researchers have found that some HEPA air cleaners can actually increase the concentration of certain VOCs in the air. This is because their design allows the dirty exhaust from inside the machine to mix with the clean air coming in.

Despite their limitations, HEPA filters are still the most effective choice for reducing exposure to airborne contaminants. When used properly, they can help reduce your threat of suffering from respiratory problems and other health concerns.

How to choose the right HEPA air filter

When buying a HEPA air filter, you should consider how large the available space is and what type of pollutants you are trying to remove.

If your room is especially large, you’ll need a larger air filter. Suppose you are trying to remove particles from a smoke-filled room. In that case, you will need an air filter with high-efficiency particulate Arresting (HEPA) and a prefilter that can easily remove the larger particles.

It’s also advisable to lay out your budget and consider the look of your residence when selecting a HEPA air purifier. Filters made from metal will be more durable than those made from other materials, but they can also look bulky and ugly if you put them in front of your windows. Some people also find that the sound of the air filter running can be irritating.

Finally, you need to decide how often you will replace the filter. If you choose a model with a long life span, you may not have to replace it very often, but it will be more expensive. If you choose a model with a short life span, you will need to replace it more often, but the unit will be cheaper.

Given these considerations, you should choose a HEPA air filter that is appropriate for your needs and fits into your budget. Look for filters from reputable brands with good reviews from users, as they are likely to last longer and work more effectively.

There are no good air filters that can be used to clean the air in your house with 100% efficiency, but they do some things very well—and other things less so. However, when used correctly, a HEPA air filter can be an effective way to reduce your exposure to airborne pollutants.


What Are Some Common Misconceptions About HEPA Filters?

There are a few common misconceptions about the effectiveness of HEPA filters which many people believe:

  • A regular filter must be replaced with a new one in order for it to work efficiently and effectively. This is not true since regular filters need only to be cleaned out and rinsed under warm water to be effective again.
  • HEPA filters are most effective at removing airborne particles that are 10 microns or larger. This is also not true as HEPA filters are able to remove a wide range of particle sizes, including 0.3 microns and larger.
  • A HEPA filter must be installed in order for an air purifier to work. This is not true since air purifiers include a HEPA filter (and other types) already installed and working for you to help improve the quality of the air inside your home or office.


What Are Some Benefits of Having A HEPA Filter?

There are several benefits to having a HEPA filter in your home or office, including:

  • HEPA filters are effective in reducing the negative health effects of 99.7% of the airborne particles measuring 0.3 microns or larger. This can help prevent respiratory problems.
  • They provide a more professional system of keeping your home or office filtered throughout the year, cutting down on airborne irritants that may be present within your space.
  • The filters are easy to clean and reuse, saving you time and money when it comes to maintaining your air quality.



1. Do I Really Need a HEPA Filter?

Answer: We all want the best in our home or office for our family, friends, and co-workers. If you suffer from allergies or respiratory problems, then the answer is likely yes – a HEPA filter is something you should strongly consider purchasing for your space.

However, if you don’t suffer from any allergies or respiratory problems and your space is relatively new and clean, then the answer may be no. It’s important to consult with a professional about your specific needs and get their expert advice before making a purchase.

2. How often do I need to replace my HEPA filter?

Answer: The HEPA filter should be replaced every 6 to 12 months, depending on the conditions and how much you use your air conditioner. You need to look at the model or brand that comes with it before deciding when is a good time for a replacement.

3. Will a HEPA filter remove dust from the air?

Answer:  No, a HEPA filter will not remove dust from the air because it only filters particles in the air that are 0.3 microns and larger in size, including pollen, pet dander, household allergens, smoke, and mold spores, etc. In order to remove common dust from the air, you will need a dust filter.

4. I have an air purifier – do I need a HEPA filter?

Answer: It depends on the make and model of your air purifier. Many air purifiers come with a HEPA filter included, but many don’t, so it’s essential to consult the manufacturer before purchasing.

5. What’s The Best Way To Ensure Your HEPA Filter Is Functioning Effectively?

Answer: The best way to ensure your HEPA filter is functioning properly and effectively is by regularly cleaning it out with warm water. This will help remove any trapped particles that your filter couldn’t get rid of on its own. You can also consult with a professional about your specific brand or model in order to get their advice.

6. What Do I Need To Know Before Buying A HEPA Filter?

Answer: It’s always best to check with a professional before making a purchase to find out which type of filter will work best for your space, the make and model of your current air purifier if you have one, etc. There are many types of HEPA filters available on the market today with different sizes, filtration abilities, and functions. You need to find out which way is going to provide the most useful results in improving your environment and making it better, or at least different from what it was before!

7. How Much Will A Good Quality HEPA Filter Cost?

Answer: The price of HEPA filters is going to vary depending on the size, quality, and brand or model. You can usually expect to pay between $30-50 for a single household use filter, but if you want higher quality, be prepared to spend closer to $70-80.

It would be best to look for a strong build and good quality materials when you are looking for a HEPA filter.

Durability is important so that the filter can last longer. The best filters also come with a warranty in case they do not work as advertised or something goes wrong with them. You should also check how often the filter needs to be replaced to make sure that it is affordable.

8. What Are Some Good Brands Of HEPA Filters?

Answer: Many good brands of HEPA filters are on the market today, including Trane, Honeywell, 3M Filtrete, Rowenta, Sharp Plasmacluster, and many more. You need to determine what one will work best for your needs or the area in which you live.

9. Do HEPA filters stop coronavirus?

Answer: No, HEPA filters do not stop coronavirus.

HEPA filters are an important part of air purification and work to remove allergens, smoke, and other particles from the air. If you are allergic to and/or endure respiratory ailments, consult with a physician before buying a HEPA filter for your space. Nevertheless, you’ll want to know that the HEPA filter does not eliminate the coronavirus.

10. How do I know if my filter is HEPA?

Answer:  Not all filters are created equal, and it is important to consult with the manufacturer of your air purifier before making a purchase to find out if the filter is indeed a HEPA filter.

The term HEPA is not trademarked, so any filter can use the term even if it doesn’t meet the true definition of a HEPA filter. A reliable way to know if your filter is a true HEPA filter is to check the Micron rating. A true HEPA filter will have a rating of .3 microns or higher.

11. Can I clean a HEPA filter?

Answer:  No, you can not clean a HEPA filter.

It is important to never clean a HEPA filter since physical filtration cannot be cleaned, and it will lose its efficiency if wet. It is also advised that you do not try to wash the outer shell of your filter, as this can cause damage to the integrity of the unit. The best way to clean your air purifier is to vacuum the outside and empty the collection bin regularly.



A HEPA filter is a certain kind of air filtration system that can remove dust, pollen, and other allergens from the air. It’s often used in places with large amounts of airborne particles like factories or hospitals because it has such low levels of resistance to airflow. The best way to understand how a HEPA filter works is by breaking down its components and seeing what each does individually.

We recommend reading this article on our blog: “What Is A HEPA Filter And How Does It Work?” You should do your research into account the benefits and drawbacks of each of the available options before making your decision about which option will best suit your needs! Home

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