Report- HEPA Filters & HEPA Air Cleaners

With all of the options available to today’s air cleaner consumer, education on the merits (and pitfalls) of air cleaning devices is a necessity. This is further required given the sometimes misleading marketing of manufacturers who convolute or overstate their technology to make the sale.

HEPA filters and HEPA Air Cleaners Comparisons

First, when looking at the filter, all HEPA filters available on the market are not the same. This is evident in many HEPA air cleaners, whereby companies use “HEPA-like”, “Bio-HEPA”, or “True” HEPA filter. These filters may or may not use HEPA media (which is typically 99.97% efficient at .3 microns), and a HEPA filter is as much about the means in which the media is sealed within the filter as it is about the media. Even if a filter has HEPA media, if it is not sealed within the frame and tested so that there is no bypass, the actual efficiency will be much less. Individually certified HEPA filters, whereby the HEPA manufacturer scans each filter and certifies the efficiency (there is a label on each filter with the test results), are the only filters assured to perform at HEPA efficiency. However, it is much more expensive to individually test HEPA filters, and this is why most air cleaner manufacturers use “HEPA-type” filters and market them as “true” HEPA. And individually certified HEPA filter ALL HEPA FILTERS USED IN TRACS AND EZ AIR ARE INDIVIDUALLY CERTIFIED TO BE 99.99% EFFICIENT AT .3 MICRONS.

The reality is that HEPA filters are the cornerstone by which hospitals, laboratories, and cleanrooms meet indoor air quality standards and guidelines. No other technology is recommended as the primary means of filtration in high-risk infection control applications (isolation rooms), operating rooms, and pharmaceutical compounding areas other than certified HEPA filtration. The Center for Disease Control, United States Pharmacopeia, JCAHO, and more all require certified HEPA filters for high-efficiency applications.

There is come confusion about the efficiency of HEPA filters because many are rated at .3 microns, so here is why they are rated at that particle size: the first HEPA filter (high-efficiency particulate air) was designed in the 1940’s as part of the Manhattan Project, where the first atomic bomb was developed during World War II. The Atomic Energy Commission (AEC – now the Nuclear Regulatory Commission) needed to know what the worst case particulate flow-through was for radioactive iodine particles in HEPA filters. This new type of filter was to be used in the production of atomic bombs and these particles could contaminate workers. Having identified 0.3-micron size particles as the most penetrating size particle and representative of the particle of concern, 0.3 microns was established as the particle size fraction at which to determine filter efficiency performance.

HOWEVER, while certified HEPA filters start at 99.97% efficient at 0.3 microns, they are virtually 100% efficient at filtering out larger particles and smaller particles (down to 0.001 microns). Some pundits look at the rated efficiency and suggest that particles smaller than .3 microns cannot be trapped by a HEPA filter, and that is just not the case. As long as you have a standard individually certified HEPA filter, like those used in TRACS and EZ Air which are 99.99% at .3 microns, sub-micron particles down to .001 microns in size can be removed with almost 100% efficiency. You do not need a “bio-HEPA”, “true-HEPA”, “HyperHEPA®”, etc.. to achieve this high efficiency at particles lower than .3 microns, as a standard certified HEPA filter is capable of removing particles down to .001 microns in size at the highest efficiency. The HEPA filter in TRACS and EZ Air would be an H13 by the EN 1822 testing method.

Furthermore, the manner in which the HEPA filter is sealed within the cabinet is crucial to any air cleaner’s functioning. You can employ the best technology in the world, but if all of the air coming into the unit doesn’t go through that technology, the overall effectiveness is minimized. The HEPA filters in TRACS and EZ Air are mechanically sealed within the cabinet to prevent air bypass, so both units perform at HEPA efficiency (99.99% at .3 microns), and each unit is tested and comes with Certificate of Performance to document that efficiency.

Moreover, the amount of HEPA media is directly correlated to the amount of time required before the filter needs to be replaced; the more media you have, the longer it will last. Many air cleaners on the market today only have 40-50 ft2 of HEPA media, and yet they claim their filters can last 5+ years. This is unrealistic if you are operating 24 hours a day, 7 days a week, as most consumers should. In TRACS and EZ Air, the HEPA filters contain 80 ft2, allowing them to last up to twice as long as competitive units.

Lastly, the only way to know when a HEPA filter needs to be changed is through measure the differential pressure across the filter. Industry standards suggest that when the differential pressure across the filter doubles due to the filter being clogged with particulate, the filter should be changed or pinhole leaks, tearing, and significantly reduced system airflow will occur. Most air cleaners on the market today utilize timers (or nothing at all) to suggest when the HEPA filter needs to be replaced, and these systems are seriously flawed given HEPA filter loading varies significantly based on the ambient conditions in the room. Consumers may, therefore, be running air cleaners that are not functioning properly for extended periods of time without even knowing it. TRACS and EZ Air, however, utilize a differential pressure switch that triggers an indicator light to inform consumers when the pressure across the filter doubles and therefore needs to be replaced.

The Benefits of UVGI – Ultraviolet Germicidal Irradiation

For the past 50+ years, UVGI has been a proven technology used for deactivating airborne and landed microorganisms in hospital and laboratory applications. Tests by the Pasteur Institute and GE Westinghouse confirmed that if the required amount of UV dosage is created (see Appendix A), bacteria, viruses, molds, and yeasts are effectively deactivated. UV dosage is a function of the intensity of the UV light, and the amount of time the microorganisms are exposed to that light (referred to as Residence Time). As such, the Center for Disease Control in their “Guide to the Control of Mycobacterium Tuberculosis”, by which most high-risk infection control policies in hospitals are based, recommends the use of UVGI in conjunction with HEPA filtration for Isolation Rooms in medical facilities. However, there are many limitations in most UV systems on the market today, as there is rarely is enough UV dosage created to destroy airborne bacteria or viruses (such as single lamp systems in high air flow units), and the lamps are not located in effective areas as they are located at the system’s exhaust (after the HEPA).

TRACS was designed to address both of these concerns. First, two lamps are mounted in a highly reflective kill chamber that amplifies the UV radiation to a level to make it effective against most airborne pathogens. The UV dosage in TRACS is 18,415 microwatt sec/cm2, allowing it to destroy airborne bacteria and viruses. However, even hospital grade UV systems rarely create enough UV dosage to destroy large airborne mold spores and some bacteria because their large size requires a very high UV dosage for complete destruction. Fortunately, due to their large size, such microorganisms can be easily trapped by the HEPA filter. However, this can present a problem in non-UV systems and units having the UV located at the exhaust.

While HEPA filters have been the standard for high-risk infection control in hospitals and laboratories (because they have been proven to remove airborne microorganisms), they require regular replacement due to biological contamination. As microorganisms collect on the HEPA filter over a long period of time, there is a risk of bacteria and mold growth on the HEPA filter as trapped bacteria/mold live, grow, and feed on each other and trapped particulate, (especially in warm and humid environments). This is sometimes called bacteria “grow-through” whereby microorganisms can live and breed on the HEPA media, and eventually even eat through the media. This ruins the integrity of the HEPA filter and possibly creates more contamination within the room as the microorganisms/mold is dispersed by the air cleaner.

However, by having the UV lamps located before and continually bathing the dirty/inlet side of the HEPA filter, the bacteria and mold collected are destroyed and deactivated over time. This is because an “infinite” residence time is produced, as the trapped bacteria/mold is exposed to the UV light as long as the unit remains on. The location of the UV lamps is part of the patents owned by TRACS Inc. In all, the UV in TRACS not only destroys airborne bacteria and disease, but it also continually radiates on the dirty side of the HEPA filter to extend HEPA filter life, ensure the destruction of larger more difficult microorganisms, and keep the HEPA filter safe for when you change the filter.

Odor & Outgassing Chemical Adsorption using Activated Carbon

Activated carbon is the standard means of removing airborne odors, outgassing chemicals, gases, and VOCs. Activated carbon is charcoal that has been treated with oxygen to open up millions of tiny pores between the carbon atoms, resulting in highly porous charcoals that have surface areas of 3,300-21,500 square feet per gram. This allows them to adsorb a wide range of airborne odors, chemicals, gases, and VOCs. When the carbon adsorbs something, it attaches to it by physical or chemical attraction. The huge surface area of activated charcoal gives it countless bonding sites, so when certain contaminants pass next to the carbon surface, they attach to the surface and are trapped. However, once all of the bonding sites are filled, activated carbon stops working, or can even begin to expel trapped odors like a saturated sponge would release trapped liquids if you continually run it under water.

The carbon filters in TRACS and EZ Air were designed for regular replacement, as carbon in any system can quickly become saturated and therefore be ineffective at removing odors, chemicals, and gasses. Even systems containing more than 10 lbs. of carbon likely need to be changed at least annually under normal conditions, or they can begin out-gassing trapped odors, chemicals, and gases. Household cleaners and air fresheners will also be adsorbed by carbon, and simple accidents or spills could cause entire carbon filters to immediately saturate and require replacement. This can be quite expensive in many air cleaners as the carbon filters can cost hundreds of dollars.

Given prefilters in any air cleaner should be changed at least quarterly to protect the HEPA filter, PAS combined the prefilter function with the need for fresh activated carbon in the TRACS/EZ Air design; instead of changing just a prefilter pad on a regular basis, a carbon pack that combines particulate and odor removal is changed. The key factor in this design is that the retail price of the TRACS/EZ Air carbon prefilter pack is actually LESS than the cost of standard prefilters in many air cleaners on the market today. Therefore, if changed regularly, (every four months), the odor, chemical, and gas adsorption in TRACS will remain at peak efficiency and effectiveness while still costing much less than larger, bulkier carbon filters. Yet the cumulative amount of fresh carbon used over the course of a year in TRACS/EZ Air is actually the same or greater than the amount of carbon used in other units (10.5 lbs would be used annually). EVERY TRACS UNIT COMES WITH A TYPICAL YEAR’S SUPPLY (THREE) OF CARBON PREFILTER PACKS

A great resource for your HEPA air cleaner/air purifier needs can be found at

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