7 Reliable Tips in Selecting the Best HEPA Filter

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You might have plans on looking for best HEPA Filter there is in the market, but before you do so, you must have an insight how it works and its application so keep reading for more insight about HEPA Filters.

Also, here’s a video that might help you understand the basic importance of a HEPA Filtration System.


The air that you breathe is filled with all manner of things, from visible dust to invisible (but stinky) chemicals. Most of these things are harmless, but some can be harmful to your health, especially for those with conditions such as asthma. For these people, relief can come in the form of a HEPA (short for “High Efficiency Particulate Arrestance or Air,” depending on who you ask) filter that removes the ick, pumping out clean, stink and dust-free air.

HEPA is a US government standard, first set in 1983. The standard says that to earn the name, a filter must capture at least 99.97 percent of particles larger than 0.3 µm (micrometers, or microns) in size, while only impeding the flow of air by a relatively small amount. The progression of modern of air filters design goes back much further, though: the technology behind them was developed to capture tiny radioactive particles released in the making of atomic bombs for the Manhattan Project in World War II. Post-war, it was used in industry, and eventually found a home in consumer devices like your air filter, vacuum cleaner and car.

Via – Appliance Science: HEPA filters and the physicsof fresh air



It is actually made from a tiny fiber glass fiber that is made into a woven paper that consist of very small sieves that can capture extremely small particles usually, used in some vacuum cleaners.


The fibers in HEPA filters (shown here as gray bars) trap dust and dirt particles in three ways. Some particles crash into filter fibers and are absorbed by impact. Some are caught as they flow along in the moving airstream, move too close to a fiber and are trapped by interception. At lower air speeds, some are trapped by diffusion(when randomly moving dust and air particles crash into one another and some are pushed into the filter fibers).


Via – HEPA filters


In order to make a HEPA filter glass fibers are used, and thanks to the unique configuration they’re arranged in air is able to pass through the filter while large contaminants such as allergens, mold or dust are captured. The pollutant particles are captured using several different principles. For the most part particles come into contact with the filter, and are then trapped based on the principle of adhesion while clean air is free to circulate.

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Other cases include contaminants being trapped after achieving partial contact with the glass fibers, or being pressed up against the filter because of the strong air flow inside the purifier. Furthermore, airborne particles are attracted by other particles which are already trapped by the HEPA filter. Thanks to these various ways of stopping contaminant particles before they are able to pass through, HEPA filters can collect 99.9% of airborne impurities as long as they’re larger than 0.3 microns in diameter.

Since most contaminants fall into that category, just imagine how much of an impact these filters have on the quality of air you breathe. Stuff like dust, allergens, pollen, dust mites, pet dander, mildew and mildew spores are eliminated with the use of a HEPA filter(especially useful for people who suffer with asthma or hay fever).

Via – How Exactly Does HEPA Filtration Work?


You may also read this article to understand more on the Effects of Decontamination Agents on HEPA Filters (PDF)

There are several types of HEPA Filters in the market and some may not be reliable as they seem and may not be applicable to you so it is very important for you to identify them and know the basic components in it so you could ask the right questions to the seller or manufacturer about it.



According to NIOSH (the US National Institute for Occupational Safety and Health), a true HEPA filter is one that can trap 99.97 percent of dust particles that are 0.3 microns in diameter (where a micron is one millionth of a meter). There’s nothing particularly significant about particles 0.3 microns in diameter: they are simply the ones most likely to get through the filter, and smaller and larger particles than this are trapped even more effectively. To put 0.3 microns in perspective, it’s worth remembering that a typical human hair is roughly 50–150 microns in diameter, so a HEPA filter is trapping dust several hundred times thinner. A genuine HEPA filter is much more hygienic than an ordinary one because it will stop mold spores and even some bacteria and viruses.

When it comes to filters used in respiratory equipment, NIOSH recognizes nine different grades, based on three different levels of efficiency (95, 99, and 99.97 percent) and three levels of resistance to filter degradation (N, R, and P). N means not resistant to oil, R is oil resistant, and P is oil proof. So you might see a filter labeled N95 (95 percent efficient and not resistant to oil) or P100 (99.97 percent efficient and oil proof).

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You might also see HEPA filters classified using the five letters A through E, based on how well they capture particles and resist airflow. Type A are the least effective that still meet the basic criteria for HEPA, while type E (at the opposite end of the scale) are military grade filters capable of coping with chemical, radiological, or biological particles. There’s also a classification based on whether filters are fire resistant (type 1) or semi-combustible (type 2).

Via – HEPA filters


The most important thing you should always consider is that HEPA-type Filters are sometimes advertised to prevent 99.9% of air contaminants that is larger than 3.0 microns but doesn’t really meet the standards so it is your responsibility to gather the facts about these HEPA Filters.


The ultra-fine, glass-fiber medium captures microscopic particles that can easily pass through other filters by a combination of diffusion, interception and inertial impaction. To meet the minimum requirements of a HEPA filter, the filter must be tested and certified to prove that it will remove at least 99.97% (9,997 out of 10,000) of particles 0.3-micron in diameter from the air passing through the filter. Particles that size are about 300 times smaller than the diameter of a human hair, and 25 to 50 times smaller than we can see. To a HEPA filter, catching a one-micron particle (1/1,000,000 of a meter) is the equivalent of stopping a cotton ball with a door screen.

Via – Facts About True HEPA Filtration


Before deciding what to buy, here are some quick tips to remember. And I highly recommend you follow these tips to ensure the efficiency of your air filtration system.



Make sure it is a “True” HEPA filter, and not just “HEPA-like”. All Surround Air purifiers include a True HEPA filter.


Make sure the HEPA air purifier comes with a germicidal UV lamp, otherwise, your HEPA filter could become a breeding ground for microbes with all the particulate it will capture. All Surround Air purifiers include a UV lamp as well.


Make sure the air purifier has strong air flow. Somewhere between 100 and 200 cfm is ideal. If it is lower than this, it will be effective for smaller spaces. If it is too high, it will be far too noisy to tolerate, while also consuming far too much electricity. Plus, if it is too high, it can push the air past the UV lamp too quickly to be properly disinfected.


Replacement costs. Know how much it will cost to replace the HEPA filter before you buy.


If possible, find a HEPA filter that comes with an ionizer. A Journal of Hygiene study found that negative ions increase the efficiency of HEPA filters. Almost every Surround Air purifier includes an ionizer.


Permanent or Cleanable versus Disposable. Most HEPA filters will last about a year before needing to be replaced. But there are permanent/cleanable HEPA filters designed to last the life of the unit. Ideally, even “permanent” HEPA filters should be replaced every 2-3 years, for optimal effectiveness. You may not get quite the same effectiveness as a HEPA that is replaced annually, but it will provide you the convenience and cost-savings of a longer-lasting filter.


Pre-filter. Although not a necessity, a pre-filter can prolong the life of a HEPA filter.

Via – About HEPA Air Filtration


You must make sure you are buying a genuine HEPA Filter from the manufacturer. Always check if you have the upper hand and know how much it would cost you for the replacement in the long run.