HEPA Filter: What It Is, What It Does and What It Doesn't Do

HEPA filters are one of the most widely-known methods of air cleaning. In fact, when most people think of an air cleaner, they think of a HEPA filter. However, HEPA filters - and ALL filters, for that matter - have limitations that must be taken into consideration when choosing an air cleaning unit for your home or office.

Because filtration systems (HEPA and other filters) dilute contaminated air with cleaner air, their effectiveness depends largely upon how much filtered air they deliver over a given period into a specified space. Consequently, most filtration-type air cleaners (they are NOT air purifiers because the cannot purify the ambient air of very small contaminants like viruses!) have large, often loud fans because they only clean the air they can actually filter through them. 

The History of HEPA Filters

HEPA is an acronym for High Efficiency Particulate Air Filter, which was used in U.S. military specifications beginning around World War II. The precise definition of a HEPA varies somewhat from country to country and from specifier to specifier with respect to the efficiency for a particular test method.

A conventional HEPA filter consists of a continuous sheet of a special paper-like, glass-fiber filter medium which is pleated into a "V" configuration with corrugated aluminum separators between the pleats. This forms the filter element, which is then bonded into a rigid frame using a special polyurethane compound. Standard filters are produced in a range of face dimensions and in two standard depths of nominally 150 mm and 300 mm.

Drawbacks to HEPA Filters

HEPA filters cannot be cleaned to remove particulate and dust loading and must be replaced as a complete assembly, often at significant yearly cost. As the particle load increases, so will the resistance to flow and hence the pressure drop across the filter. In some applications, uneven filter loading will cause non-uniform airflow through the filter and decreased effectiveness. Additionally, inexpensive HEPA filter systems often do not seal the filter chamber properly, so contaminated air simply passes through the holes and back into the ambient air.

Some manufacturers will void your warranty on filtration systems if you do not replace the filter according to a very specific schedule, and most will not cover damage caused to the unit by clogged filters, which can cause the fan motor to burn up.

Even the larger HEPA air filters cover only a single room, or at most a small apartment. This is because in order for the air to be cleaned, it must pass through the filter. As a result, they can only clean the air that is nearby. While some filtration systems do incorporate flimsy charcoal or other filtration media that can absorb odors, they tend to have little effect on odors and virtually none on bacteria, viruses, germs and fungi like mold.

Other Disadvantages to Filtration Systems

• HEPA filters are extremely fragile and can easily be damaged during installation, cleaning, and even when the unit is moved. HEPA filters should be tested at least annually. Replacement filters can cost as much as $200 (average is $75 - $150). Many air cleaner brands using HEPA filters now require that you change the filters at least once and often twice a year in order to validate the unit's warranty. 
• HEPA units are usually loud - often sounding like a window air conditioner. Some even sound like small lawnmowers!
• HEPA filters are costly to operate - from $100 - $300 annually in energy usage. Filter-less air purification devices cost, on average, approximately $30 to 50 per year to operate.
• HEPA filters may cost less "up front," but actually purify less air, less effectively. Cost per square foot of filtration with a HEPA unit ranges from .35 cents to as much as $1.10 (or more); filter-less air purifiers units average .18 - .25 cents per square foot (not including electricity costs).

A key point to consider is that HEPA filters are simply that -- filters -- and are designed ONLY to FILTER larger (0.3 and above) micron-sized particulates from the air, and they can do it quickly. It is true that they can remove mold spores and bacteria from the air, but unless the filter is treated with an anti-microbial substance -- which is often, in itself, a contaminant -- the still-living microbials continue to grow and multiply on the HEPA filter. And when you pull out the filter to change it, guess where those microbials go.

Some air cleaner models offer optional filters for smoke and odors, but these simply trap chemicals and odor vapors in activated charcoal or carbon, and are not very effective unless they have a sizeable carbon, like in the Airpura models. However, it is nearly impossible to know at what point the carbon becomes saturated and can no longer absorber chemicals and odors.

By contrast, filter-less air purification devices based on Germicidal UV technology, like the Air Oasis, oxidize odors and vapors, removing them permanently, and they are effective on even microscopic particulates, bacteria, and viruses as small as .001 microns (many viruses, herbicides and pesticides are that small).

HEPA filter effectiveness significantly diminishes as the particles become smaller. As particles become very small, they cease to behave so much like particles as they do gas phase molecules. It is difficult to tell whether such small particles are actually suspended in air (particles) or diffused throughout it (gas or vapor). The bottom boundary where particles act as true particles is about 0.01 micron. The normal theory of separation does not apply to particles below this size and removing them from air requires techniques reserved for gaseous materials, like the Air Oasis technology. Particles above 0.01 micron are usually considered to be filterable. Particulates smaller than 0.01 include pesticides, herbicides, some atmospheric dust and nearly all viruses. Plus HEPA filters do not remove gases or VOCs (volatile organic chemical) off gassed from most new carpeting, building materials, furniture, etc.

To see the actual micron size of common particles
found in your home Click Here

We offer two brands that include HEPA filtration in combination with other technologies. Surround models are great for residential applications, while Airpura are excellent for larger spaces and commercial applications:

Airpura Commercial HEPA and Carbon Air Cleaners

Airpura is a completely new air cleaner with all the design improvements lacking in other similar technology systems. Airpura design principles include a simplified unobstructed air flow for quieter more efficient performance and reduced noise. The prefilter can be vacuumed through the mesh for easy monthly maintenance, then replaced every 12 months. Two special microbial (bacteria and viruses) suppressing filters help to protect the hefty 18 or 26 pound carbon bed. Felt gaskets are used to seal the filter chamber, eliminating rubber seal off gassing. The metal capped HEPA filter removes the possibility of any plastic vapors from non-metal caps.

Airpura uses a powerful, variable speed integrated fan/motor, letting you choose the rate you clean your air from super quiet to premium power filtering with 560 CFM capacity. With Airpura's effective pressure sealed filter chamber, all air is filtered; NO particles or gases escape. Other systems allow leakage and can't achieve the claimed 99.97% HEPA efficiency. And, Airpura offers the cleanest air, using superior quality true HEPA and activated carbon (special carbon blends are available) with optional UV sterilization to deliver truly clean air for home, office and industrial applications. Airpura is available in eight models and three colors: Cream, white and black. more info

Surround Air Multi-Tech Ionizers

Negative ions clean the air by magnetically attracting to pollutants until these newly-formed larger particles become too heavy to remain in the air you breathe and they fall to the ground. Surround Air Ionizers continually produce negative ions, without creating the "black-wall" effect of older ionization technologies, so even if one of these fallen particles is kicked up into the air, it is quickly removed again. The most important thing, though, is that they are taken out of the air, preventing you from inhaling them into your lungs, which is how they cause problems.

Since certain technologies are much better than others at removing different types of air pollutants, all Surround Ionizers are multi-technology. All models include ionization, a prefilter, a HEPA and Carbon Filter and UV lamp, plus some models include a TiO2 filter or an optional ozone sanitizer. And, the Intelli-Pro includes electronic sensors. With Surround, you get the best of the most advanced air purification technologies on the market, all rolled into one air purifier. The best part is that Surround Multi-tech ionizers and replacement filters are affordable for every budget. more info

Venmar Air and Humidity Ventilation

For the past two decades mounting evidence suggests that dependence on the natural exchange of air between the indoors and outdoors through air infiltration and exfiltration may not be sufficient for good moisture control and indoor air quality. It also has become increasingly obvious that traditional ventilation methods, like opening a window or use of a common bath fan, are not providing adequate ventilation. A properly designed and installed ventilation system is the key to positive moisture control and will help ensure a healthy indoor environment for the occupant.

The solution is heat recovery ventilators (HRV) and energy recovery ventilators (ERV). These mechanical ventilation systems use fans to maintain a low-velocity flow of fresh outdoor air into the house (incoming air stream) while exhausting out an equal amount of stale indoor air (exhaust air stream). Fresh air is supplied to all levels of the house while stale air is removed from areas with high levels of pollutants and moisture. more info

Filter-less Ways to Remove Particulate

Filter-less Air Purification devices rely on special UV technology that creates unique oxidizers -- for instance, Hydroxyl ions, hydro peroxides, super oxide ions, passive negative ions hydroxides and ozonide ions -- that seek out and destroy odors and contaminants throughout your home. They can effectively remove the particulate like dust, pollen and dander, although not at quickly as can be removed by a large, noisy fan-based filter. However, they are significantly quieter and have very low maintenance (replace the cell once every three years).

The Air Oasis Induct works with a HVAC system ductwork to provide whole-home purification. (AC systems also remove beneficial negative ions from the air; Air Oasis units replace them, giving you better sleep quality, enhanced mood and superior air purification). With oxidation air purification technology, all you ever replace is the lamp once a year with most models on the market, or once every 3 years with Air Oasis Air Purifiers.

Air Oasis Breakthrough G3 UV Air Purification Technology!

No air purifier on the market can compete in effectiveness, energy efficiency, adaptability and quiet operation, when compared to the Air Oasis G3 patent-pending Nano Nickel HCT photocatalytic oxidation technology. Other oxidation brands use only titanium dioxide (TiO2) as a catalyst, the cheapest, most available catalyst metal on the market, whereas Air Oasis contains five rare catalyst metals and nano size metals to increase the kinetic rate of reaction.

Unlike HEPA filters that only remove some particulate and carbon filters that only remove chemicals, VOCs and odors, Air Oasis technology is proven effective against MRSA, bacteria, molds, VOCs, chemicals, gases, odors, pollen, dander and more. Extensive testing conducted by West Texas A&M University at BSA Hospital confirm that Air Oasis not only purifies your air, but sanitizes surfaces, too. Additionally, Air Oasis Air Purifers are made in the USA, using brushed aluminum casings and UV lamps that utilize a proprietary long life coating, allowing them to outlast any UV lamp on the market. Read More about Air Oasis G3 Air Purifiers

Find the Right Air Purifier for
Your Unique Problem or Application

It's no mystery that the air inside our homes, offices and nearly every building we enter is contaminated with toxic air pollution problems. But wading through the plethora of air purification technologies and models to make our living and working space free of pollution can be a daunting task, especially with the misinformation presented by so many salespeople and web sites. There are many different air purification technologies and air filters on the market, but no one air purifier technology can solve every air pollution problem, which is why we carry different brands. For help determining which air purifier is right for you, click on one of the below links or call us toll free at 866-875-4386 (US and Canada).

Air Purifiers: by Problem - by Technology - by Brand - Air Purifier Buying Guide 

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