What is a HEPA Air Purifier?

A HEPA grade purifier is an air cleaning machine that is engineered containing a High-Efficiency Particulate Arrestance cleaning filter. It is a reputable beneficial appliance in homes with asthma patients and generally allergy-inclined people. These machines are useful to anyone who wants to breathe happily in their home. In fact, the Environment Protection Agency found that the level of air pollutants in your home is often two to five times higher than outdoor levels.

You might be wondering what exactly is in an air purifier?

An air purifier is a portable machine that you put in your house, that cleans the air with a filter. So if you're spending a lot of time indoors, you may want to invest in an air purifier. If you have a problem with dust or smoke, a respiratory system condition - this is the machine that will solve the problem.

Did you know that an air purifier can catch all the stuff floating through the air in your home and it also catches particles that cannot be cleaned any other way?

To get clean air you need to buy an air purifier with a good filter. There are a lot of different models out there. But when you buy an air purifier, always check that among other filters (basic, charcoal, anti-bacterial) it also has a high-efficiency particulate arrestance filter.

Why is HEPA any different than a traditional, anti-bacterial or charcoal air filter?

Compared to a regular furnace filter (that only captures large and medium dust particles), the HEPA grade filters capture everything from the size of a pollen grain down to virus particles (virions) and smoke (a mix of airborne solid and liquid particulates). Traditional air filters simply do not possess the capacity to eradicate tiny micron size particles from the indoor air.

HEPA is a standard performance for any Association of Home Appliance Manufacturers verified machine. Keep in mind, anything not as HEPA level will not clean your home air from a range of finely dispersed particulate.

HEPA Construction

The construction and materials of HEPA filters are in continuous development. The results are less airflow resistance and lower energy consumption. HEPA filters are built with a net of randomly intertwined fibers. Filter fibers are made of micro glass fiber paper, that are between 0.5 and 2.0 micrometers in diameter. Generally, HEPA filters are very well-constructed and have proven their sturdy quality even under critical conditions. HEPA filters are very reliable thanks to the strict quality control and production standards.

HEPA Process

Being an essential part of pharmaceutical, healthcare, food industries and in micromechanics: everywhere where sterile environments are mandatory.

The HEPA system is a few stage process that is started out by filtering the larger particles through a sieving mechanism. The next step takes air through a finer mesh fiber to take out smaller particles. To complete the particle capturing process the air flow is taken through a fiber collider.

Once the air comes out of a HEPA grade filter, it is supposed to be deprived of 99.97% of contaminants and airborne particles.

HEPA Scale

To put into perspective a human eye can detect a particle that is 10 micron in size. Pollen grains and plant spores are still visible to the eye with a considerably precise detection. But let's take a look at other particles that float in the air of a home, hospital, school. Bacteria is usually as small as 0.3 microns. Viruses are as well. Even though they usually do not float air on their own but on the microparticles of organic materials from human bodies, like spit. This is the number one reason why HEPA filters are so widely used in the pharmaceutical industry and medicine. Airborne virons are very easily spread through the air that was not properly HEPA filtered.

A significant reason why a 0.3 micron HEPA is used in pharmaceutical companies is that in research labs full of scientists, medical staff and clinicians who work with bacteria and viruses the air should be as clean as it possibly can be to contain the research particles. In operation theaters and surgery rooms where open wounds are handled, it is necessary to avoid as much airborne bacteria and virons as possible to avoid severe intrabody contamination.

Authentic HEPA Air Purifiers

The idea of High-Efficiency Particulate Arrestance air purification was implemented originally back in the 40s of the last century. At the time of nuclear weapon testing and the military project required a machine that would filter out radiation particles from the air.

It eventually turned out that HEPA did almost nothing to clarify air of radiation, but it was discovered that the filter cleared the air of almost every possible airborne contaminant there was. The brilliant air purifying innovation idea hit the commercial cleaners market in ten years. By 1951 the term HEPA became a trademark and became a widely-used descriptor word to define highly efficient air filters.

These days genuine HEPA grade filters have grown immensely in structure, material quality, and work stability. To define a true HEPA grade filter you need to make sure there is a real HEPA filter built into the machine you're shopping for. Avoid buying items that are marketed as HEPA-like or HEPA-type. Search for providers and manufacturers that have been on the market for a while and would unlikely sacrifice their reputation.

True HEPA Filtration

In order to meet the HEPA grade requirements and wear a HEPA label, air purifier machines of a manufacturer have to first follow through a strict multi-stage standardization procedure. This is done to comply with demands set by the U.S. Department of Energy. According to the requirements, the alleged HEPA purifier must have the capacity to capture up to 99.97% of airborne particles that vary in origin. If an air purification machine has been manufactured, tested, certified, and labeled according to current HEPA standards, it will arrest all particles that are even 0.3 microns small. For the sake of reference, 0.3 microns equals 0.000012-inch.

What makes HEPA so effective?

HEPA filters are built with fiberglass ultra-thin folded medium that rotates and while doing so-captures super fine airborne particles. Interception, diffusion and inertial impact are the factors that manage to arrest the airborne contaminants so well.

Upon being manufactured, all HEPA filter is being thoroughly tested. Just being produced a HEPA kind does not prove its utmost efficiency. Any kind of manufacturing defect, even a collection or transportation mistake may jeopardize the purifier's performance and functionality. If every HEPA filter has not been properly tested, significant leakage can go undetected. Inspection and assessment of every filter is the only way to meet the industry standards in the field. The recommended practices for High-Efficiency Particulate Arrestance air filters (performance, maintenance, functionality, labeling) are controlled and monitored by the Institute of Environmental Sciences and Technology (IEST) and Underwriters Laboratories (UL). The major requirements are as follows: testing HEPA media, testing HEPA media and construction, HEPA filter leak tests, testing and certification for flammability requirements.

Where do they use High-Efficiency Particulate Arrestance air filters?

Since a standard HEPA filter works as a thorough mesh to capture the finest airborne particles from the airflow. These high-efficiency air cleaning machines are used in a variety of enterprise facilities, office buildings, in simple homes, in clinics and nursing homes, in kindergartens and at microelectronics plants, research laboratories, surgery rooms. And since HEPA comply with current CDC Guidelines for Environmental Infection Control, they are recommended for Healthcare facility usage too; they capture pathogens (bacteria, viruses) and clear the air of allergens and contaminants.

How do HEPA Filters Manage to Trap all the Fine Particulate?

The simplest, a traditional air filter is a sieve that catches larger dust, fuzz, dirt particles. To catch the tiniest bits you'd need to put several filters like that on top of one another. That in its turn would cause the system slowdown. Larger amounts of energy would be necessary to run the filter. And, it would easily clog and breakdown if it was constructed that way.

As it was mentioned above, HEPA filters have a radically different structure. It uses three physical powers to arrest the 0.3-micron airborne particulate efficiently.

Who is HEPA recommended for?

The biggest benefits of a standard HEPA would be very noticeable for someone with severe respiratory allergies or bronchial asthma.

The second group of people, who'd benefit from a HEPA is elderly, weak people and babies.

A dusty home, a home that is poorly ventilated, a home with a few pets and thus having odors wandering through it would appreciate a HEPA with an activated carbon filter. A truly detrimental effect is made onto mold, bacteria, and viruses by a UV light inclusive air purifier.

What is the basic efficiency testing for a HEPA air purifier?

Regular efficiency testing, performance control, general maintenance, and filter replacement, are strongly recommended. We suggest going for the first circuit of performance control in about six months after your purchase and initial installation. Since HEPA air purifiers are supposed to run 24/7, regular checkups, filter cleaning/replacement are crucial. The regular technician visits for functionality control are recommended for any HEPA filter, whether it has been installed in a business facility or in a regular home. It is of common knowledge that HEPA filters wear down and are supposed to be fully replaced in two years time.

What are the Requirements for the Shell of a HEPA Filter? If There are any?

We recommend our clients to go ahead and pick how their air purifier will look at themselves. Consider your interior design and the placement of the machine.

At the same time, we are aware of the potential possibility of spoilage of any types of frames and shells for HEPA filters apart from the metal ones. By all means, metal filter frames are considered to be the easiest to maintain and the most hygienic. We believe that if the wooden outer shell of an air purifier is left clean and dry, it should not be disturbed by any damage whatsoever. If you choose to be extra cautious and avoid potential microbial or allergen air contamination, we recommend picking the metal framed or plastic framed models of HEPA air purifiers.

Do Air Purifiers meet the CDC infection control requirements, IEST and UL requirements?

Centers of disease control and prevention, Institute of Environmental Sciences and Technology and UL LLC (Underwriters Laboratories) have issued a set of requirements for all kinds of air filters, including HEPA grade air filters. Filters have met the requirements, some of our filters even exceeded those. Ecoquest HEPA air filters have been tested and certified as being 99,99% effective at cleaning indoor air of pollutants, allergens, bacteria, contaminants, dust, fuzz and dirt. The high-efficiency filters clean the air of 0.3-micron-sized pollutants effectively. The lowest permissible leakage of dust particles contains three out of ten thousand particles. In the case of Ecoquest HEPA filters, this rate is an even lesser amount.

Are there any additional benefits that Ecoquest HEPAs provide to the customer?

Microglass media in high-efficiency air purifiers is created on the basis of IEST engineering requirements and UL900 flammability demands.

Most air filters need replacement. At some point in their life span, some filters that are made of cellulose material can work as a harbor for a variety of bacteria and contaminants. To prevent the increasing growth of bacteria and not to compromise the filter safety itself Ecoquest had created a coating for their filter media that possesses a powerful antimicrobial effect and protects the wholeness of the filter construction.

How often do I need to replace HEPA filters?

Air purifiers have a set of definitive guides as for the replacement timelines. The cellulose filters need to be fully replaced. The fiberglass filters need to be thoroughly maintained and cleaned regularly. There is a perception in the industry that the air filter cleaning schedule should be based on the employment fashion.

It is considered normal for a HEPA air filter to run all the time. That means that you keep the air purifier on at all times, 24/7. Experts claim that efficient room air cleaning happens when the machine has taken the whole amount of air through the filter three times. With that being said, let's not forget of all the new airborne particulate that enters the room every time the door opens or a person, a pet comes in.

Regular fiberglass filter cleaning is a rather simple process. The filter itself and the outer filter shell needs to be washed with a brush and warm soapy water. Then rinsed after. If your HEPA purifier stands in the living room where most of your family spends their time, make sure to wash up at least once a month. If the air outside is especially harsh, either wash the filters more often or apply Ecoquest add-ons: harsh environment pads.

Air harshness, use duration, the density of airborne particulate, humidity and many other factors impact the cleaning and maintenance frequency.

Is there a way to improve my HEPA filter functionality?

As good as Ecoquest HEPA are, there is still a way to fix them up a little bit. To improve the functionality and prolong the longevity of your HEPA filter, try to add on lint screens, charcoal screens, activated carbon filters, and harsh environment pads.

What is the best HEPA filter placement?

The free-standing devices for air cleaning may not be a part of your overall house HVAC system, but they are a great addition to your home nonetheless. They remove all contaminants from your indoor air and, in fact, do the job that no one else does or can do.


To achieve the best filter placement and get the most bang for your hard-earned money Ecoquest recommends to do a little logistics around your house and figure out what is the most used room in the building? Think about all the people that may benefit most from an air purifier installed in their room: a baby, an elderly, a sick person, a bedroom maybe?

The best way to place a powerful HEPA air purifier would be around the major air intake flow. If you have an air conditioning unit - place your HEPA right beside it. This way air gets fully cleaned into your lungs.


If you have a smoker in the house, consider placing a separate air filtering machine with activated charcoal beside him. No matter the amount of smoke he produces, the air will get cleaner faster and the filter will absorb the pathogenic gas. Getting rid of a filter that is meant to absorb smoke and strong odors is crucial. Provide a replacement for such a filter more often than usual.


Kitchens and bathrooms are well-known air filter destinations. Intense continuous humidity, odors, mold, allergens, perfumes, cooking smokes, airborne grease particles, food scents, etc can jeopardize any homely atmosphere. Placing a high-efficiency particulate arrestance air filter on top of the kitchen cabinet where the cooking happens will remove smoke, scent, and grease from the air and reduce the odors associated with cooking. A purifier can also negatively impact the mold growth in your bathroom and make the air in your bathroom much fresher.

Things to consider before buying

If you are an asthma patient or an allergy sufferer, buying the most advanced air purifier may not save you. We mean that relying upon an air purifier itself is no good. A HEPA air purification machine can still improve your condition and breathing considerably.

The key thing to take into consideration before you buy though is the manufacturer, the licensing and the authenticity. Make sure that the air purifier you're getting is a true HEPA. Not HEPA-like or HEPA-type. The air purifier you're getting should be able to capture 99/97% of 0.3 airborne particulates from the air, full stop. Make sure the machine has a label that says that.

Air purifiers with HEPA filtration may have a higher energy consumption if compared to a traditional air filtering machine. A HEPA filter still needs regular maintenance, cleaning, and filter replacements. Ask the consultant of your options, let him show you around. Get a glimpse of the pricing for the replacement items for your HEPA filter model.

Ask warranty questions. Even if you're buying a refurbished HEPA air purifier. Confirm with your provider that you still have the warranty protection running for the machine you're getting. If you chose to maintain and clean your HEPA air filtering machine on your own, follow the manufacturer's instructions on checking the filter condition, disassembly, and cleaning.

HEPA from Ecoquest. Stages of Indoor Air Cleaning

The basis of any HEPA-filter is randomly arranged fibers of different thickness, about 0.5-5 microns. The distance between the fibers is about 5-50 microns. The diameter of fine particles lays within a few microns or even several fractions of a micron.

Ecoquest Air Purifiers include several air cleansing stages.

Stage one: pre-filter that catches large particles from the air: lint, pet hair, dander, bigger dust particles.


Stage two: Charcoal filter and Activated Carbon Filter. These are the filters that are taking out all the nasty scents from your home, kitchen, lavatory. Keep in mind that the principle of an odor absorbing filter lies in the filter's nature


Stage three: the HEPA filter with Antibacterial treatment, it works effectively to eliminate dust, pollen, mold spores, smoke (cigarettes, cooking, open fires), pet dander, odors, bacteria, germs, allergens. This stage is able to filter air pollution of 0.3 microns. All those particles get trapped in the filter.

A High-Efficiency HEPA filter enables the purifier machine to capture up to 99.97% of dust, allergens and other solid airborne pollutant particles that are sometimes as small as 0.1 microns.

How does the HEPA filter catch the finest particulate?

The main difference between HEPA from other filters is that particles do not have to be stuck in the fibers to filter. If the speck of dust just touched the filter material, this is sufficient for it to be effectively trapped in the filter. This is due to two processes: adhesion and autohesion.

Adhesion is the interaction of dust with a precipitating surface, in our case with HEPA fibers. Due to the adhesion on clean fibers, the first layer of dust appears. Autohesion, or stickiness - is the interaction of dust particles with each other. Due to the autogenous interaction, the particles continue to accumulate on each other, forming multi-layer conglomerates on the fibers. They look something like this:

Thanks to the forces of attraction (Van der Waals force), the particle almost adheres to the HEPA filter fiber, just touch its surface. This explains the retention of particles on the filter, but there is still no answer to the question:

How do the smallest particles touch the fiber of a HEPA filter?

As we found out, the effect of the sieve has nothing to do with it - the smallest particles freely fly through the pores. There are other mechanisms in the HEPA filters.

Any particle is held in the air flow, and if there are no forces in the filter deflecting the particle from the air flow line towards the fiber, then there will be no deposition. As a result, the particle will slip through the filter along with the flow.

Depending on the size and mass of the particle they leave the airflow and stick to the filter differently.
The smallest particles (with a diameter of fewer than 0.1 μm) have a small mass and are constantly in a chaotic Brownian motion. Their movement pattern constantly fluctuates in accordance with the air flow. While the particle rotates it leaves the flow, touches the fiber and settles down. This is the diffusion effect:

Larger particles (with a diameter greater than 0.3 microns) weigh more, so they rotate in a much weaker fashion or do not rotate at all. These particles are deposited by another mechanism. The model shows that the airflow lines are bent near the fiber, bending around an obstacle. Large and heavy particles collide with the fiber and are deposited thanks to inertia. This is the effect:
Diffusion and inertia complement each other: one is responsible for filtering the smallest particles, the other larger ones:

What does the effectiveness of the HEPA filter depend on?

The effectiveness of HEPA depends not only on the size of the particles being filtered but also on the parameters of the filter itself:

  • fiber diameter in the HEPA filter
  • fiber packing density
  • fiber material.

The thinner the fibers are, the denser they are packed, the greater the area of their contact with the particles. And the better the fibers cling together, the more effective the settling. If the filter material is highly conductive then the fibers can be charged in the air stream. In this case, electrostatic attraction forces (Coulomb forces) appear between the fibers and particles. They increase the effectiveness of the HEPA filter further. As particles are settling down, the distance between the fibers decreases. It looks something like this:
As a result, the overall fiber surface increases, and, incredibly so, over time, the efficacy of HEPA does not decrease, it grows. On the other hand, when the filter gets rather dirty, the airflow resistance of the filter increases and, as a result, the performance of the device goes down. If the filter is completely clogged and the machine's performance drops to almost zero, the only way out is to replace the filter. Replacement frequency depends on filter capacity. Overall filter capacity determines how much dust can settle down in a HEPA before the pressure drop across the machine becomes critical.

Conclusion

Now, when we have an idea about the HEPA-filter, let's put together its working principles:


  1. air flow with various size dust particles, from 10 microns and less gets into the filter;

  2. large particles settle from the air flow due to inertia, small particles settle due to diffusion;

  3. all particles that have left the air flow and touched the fiber settle on the filter;

  4. particles are firmly held on the fiber due to the forces of attraction (Van der Waals).


All the unobvious facts about the HEPA filter:

  • a HEPA filter can trap particles of all sizes;

  • dust is trapped in the HEPA filter almost forever

  • HEPA vacuuming is useless - just replace the filter when fully clogged;

  • the effectiveness of the HEPA filter only grows over time.

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