What are HEPA Filters? - Absolute HEPA Air Filters

What is a HEPA Filter?

(and other common Questions about HEPA Filters)
We see a lot of "Garbage", "Junk Science" and some of the most FALSE statements used to sell products other than HEPA filters on the internet. These un-educated sellers are trying to make Allergy and Asthma sufferers, and other consumers, think that HEPA filters are no good. To quote some incorrect and false phrases we have seen: "HEPA filters are not effective." , "Air filters don't work very well", "HEPA and Activated Carbon Filters don't work" , AND one of the most FALSE STATEMENTS MADE TO MAKE A BUCK: "Ozone is much more effective than HEPA filters. HEPA Filters only create a breeding ground for pathogens, such as molds and bacteria." ALL of the above statements are FALSE!

You should notice that when you see these highly un-true and false statements it is usually from ionic type or ionizing ozone air purifier sellers or dealers and that is all they sell. They are simply trying to scare you and mis-lead you into thinking that HEPA filters can not filter the air. These are mis-leading and unethical sales tactics that are used simply to sell their ozone products.

INDISPUTABLE FACTS: Ozone is a lung irritant that is emitted from ionic air cleaners, ozone air purifiers, UV below 240 nm, and many electronic air cleaners. Even small amounts of ozone are undesirable for allergy and asthma sufferers. The EPA, American Lung Assoc. and others do NOT recommend Ozone usage be used in occupied spaces such as homes and offices. While ozone is a method for reducing mild odors in non-occupied areas it DOES NOT remove airborne particles such as Dust, Dander, Pollen and mold, it also does not kill dust mites! AND , these sellers have NO VERIFIABLE third party laboratory test proof of the Claims they make. They also have no reputable health organisations that will support or recommend their product. CLICK HERE TO SEE A RECENT EVALUATION ON OZONE AIR PURIFIER SAFETY!

Cleck Here for MORE Links on why you should stay away from ozone generating devices!

Consumer Reports Magazine in the May 2005 issue found that ionic and ionizing types of machines they tested were INEFFECTIVE in removing dust, cigarette smoke and pollen from the air and also found that they release potentially unhealthy levels of ozone.. For the FULL article please see the May 2005 Consumers Report Magazine.

Allergy and Asthma suffers need to know the true facts. This is why Allergists and Doctors ONLY recommend true HEPA air filtering and air cleaning systems over any other.

The following quote from the Allergy and Asthma Network sums it up perfectly:

"There is only one air cleaning method Approved and Required in circumstances where human life, health, or safety is dependent upon cleaning relatively large volumes of air. That method is used in patient isolators (boy-in-the-bubble), orthopedic operating rooms, hospital pharmacy preparation of I.V. add mixtures, biological safety cabinets for infectious disease research, to contain radioactive particles, and in pharmaceutical production facilities to ensure the purity of medications. That one method is TRUE HEPA filtration." - Allergy and Asthma Network - Mothers of Asthmatics, Inc.
News: November 2001 : Exposure to airborne indoor fungi in residential environments can be reduced through use of portable high efficiency particulate air HEPA filter and regular maintenance of filter material and carpets.

Cedric Cheong of Murdoch University in Australia presented this new research at a IAQ 2001 conference.

"Our study showed a 70 percent reduction in airborne indoor fungal levels and a 38 percent reduction in particulate matter in homes fitted with portable HEPA filtration units." In Cheong's paper entitled The Use of HEPA Filters to Control Airborne Indoor Fungi, Cheong stated: " These results show that the operation of portable HEPA filtration units achieve effective outcomes in reducing levels of airborne indoor fungi. Outdoor sources remain the main contributor to indoor sources of fungi."

The study involved asthmatic children between the ages of 6 and 11. Portable HEPA air cleaners were placed in the children's bedrooms for 15 weeks. He added that the ongoing study results are being documented by a physician, not self-reported. In one of the 15 homes being studied, a HEPA air filter has decreased asthma symptoms and medication of an asthmatic child.

Also, HEPA filtration technology is currently the only type of air purification tool recommended by the U.S. Government's Department of Homeland Security.


What is a TRUE HEPA Filter?

The Letters in the wordHEPA stand for High Efficiency Particulate Arrestance.(You may see others saying that the A means Arresting, Arrestor or Air but they all have the same basic meaning: "to capture") A "True" HEPA Filter is also known as an ABSOLUTE Filter because of it's efficiency!

The "True" HEPA filter was developed during World War II by the Atomic Energy Commission and it was designed to remove and capture radioactive dust particles from the air which might escape and present a health hazard to the researchers. The "True" HEPA filter was specifically designed to protect the Human Respiratory System. Even the CDC guidelines for the transmission of tuberculosis (TB) recommend that only HEPA filters with an efficiency of 99.97% tested at 0.3 microns particle size or smaller be used.

The "True" HEPA filter is recognized byOSHA / EPA as the ULTIMATE in cleansing the air and is a proven method.

The "True" HEPAfiltration technology is currently the only type of air purification tool recommended by the U.S. Government's Department of Homeland Security and FEMA. (Austin Air HEPA Air Cleaners have been chosen by the Department of Homeland Security, FEMA, and to aid the victims of the September 11th Terrorist Attacks.)

"True" HEPA filters are regarded as the best form of air filtration. Hospitals, laboratories, even NASA spend many thousands and even millions of dollars to create contamination free environments called clean rooms to help eliminate foreign particles, infectious agents, heavy metal particles, and a variety of other undesirable contaminants.

For a filter to be called a "True" HEPA , it must retain and filter out all particles from the air that passes through it down to 0.3 microns in size at an efficiency rating of 99.97%.

A "True" HEPA Filters's efficiency DOES NOT decrease during it's life, it actually increases and its also known as an ABSOLUTE type filter media for particle capturing.

For a filter to be labeled "True" HEPA , it must be certified 99.97%efficient in capturing 0.3 micron (not 0.1 or 0.01 etc..) respirable-size-particles (RSP) according to the U.S. Military Standard MIL-STD-282, commonly known as the DOP test.  The reason 0.3 micron is used and no other is because 0.3 micron is the size at which all mechanical filters are LEAST efficient in capturing. Other methods of testing do not give a true picture of efficiencies relative to respirable-size-particle (RSP) capture.

"True" HEPA filtration is recognized as one of the most efficient air filtration methods known and proven to remove airborne particles, down to the size of 0.3 microns, and is almost exclusively used in medical, laboratory, and commercial applications where totally clean air environments are required for human health and safety.

"True" HEPA filters are used for nuclear contamination, lead and asbestos abatement, surgical facilities, tuberculosis wards, clean rooms, computer rooms and other areas where clean and particle free air is essential.

Since 0.3 micron size particles are the most difficult size particles to remove from the air (not 0.1 or 0.01 or any other number) and theypass easily into the body's respiratory system, (RSP) they are specifically used in the testing and certifying of a "True" HEPA Filter.

(Please note: "HEPA-Type" filters are lower cost, not as efficient, and not an equivalent to a "TRUE" HEPA filter. "HEPA-Type" filters are simple low cost impersonators of a "TRUE" HEPA filter.)

Is 0.3 Microns Filtration Important?

YES! Particles that are0.3 micron in size are the most difficult particles to trap and contain within a filter. Also,0.3 micron particle, when inhaled, passes easily into the body's respiratory system so the body's natural defense system is more vulnerable to these small particles. This is why ONLY  "True" HEPA filters are recommended by Allergists and Doctors.

What's a Micron?

A micron is a measure of length: "1 micron equals 1 millionth of a meter!".

A particle that is 10 microns or less in size is not visible to the naked human eye.

Examples of some common air contaminants and their size in microns:

  • Human Hair ........................................ (70 - 100 microns)
  • Human Sneeze ................................ (10 - 100 microns)
  • Pet Dander ........................................ (0.5 - 100 microns)
  • Pollen ................................................. (5 - 100 microns)
  • Spores from Plants .......................... (6 - 100 microns)
  • Mold ...................................................... (2 - 20 microns)
  • Tobacco Smoke ................................. (.01 - 1 micron)
  • Dust Mite Debris .............................. (0.5 - 50 microns)
  • Household Dust ................................ (.05 - 100 microns)
  • Skin Flakes ..................................... (0.4 - 10 microns)
  • Bacteria ............................................. (0.35 - 10 microns)
  • Viruses ............................................. (.002 to 0.3 microns)
When living organisms such as BACTERIA and VIRUSES are captured by a True HEPA filter, are they killed?

"True" HEPA filters provide a DRY environment and captured bacteria and virus will dry out because without moisture, there is nothing to facilitate their growth and keep them alive. Without moisture the bacteria will die. Bacteria can breed within the filter ONLY if the air coming into the filter is moist. Other methods for killing Bacteria within a "True" HEPA filter is if the filter has been SPECIALLY treated for killing bacteria OR there is a Germicidal (non-ozone) Ultra Violet light such as with the Airpura Air Cleaners w/ UV.

Will a True HEPA Capture and Trap ALL Viruses??

NO, most all Viruses are much smaller than 0.3 microns and they can pass through a HEPA filter. Some may get trapped by adhering to the HEPA media but can also break loose and return to the air. According to the EPA there is no standardized test available to measure the effectiveness of virus filtration.

Is a "HEPA-Type" Filter the same as a "True HEPA" Filter?

NO!! HEPA-Type filters look like a genuine"True" HEPA but have nonspecific filter efficiency for respirable size particles (RSP) (0.3 microns) anywhere from 25% to 95% whereas a"True" HEPA has a certified 99.97%efficient in capturing 0.3 micronparticles . (This info provided by Allergy and Asthma Network - Mothers of Asthmatics, Inc)

Should I leave my HEPA air cleaner on all of the time?

YES ! Leaving the unit ON even when you are away lets the unit constantly scrub the air. Also, if a unit is turned off for a long period of time and then turned back on, you may smell some of the captured particles within the HEPA and or carbon. You should ALWAYS leave a HEPA unit running 24/7. If you do turn it off for days and weeks you are best to also change the filters. Most people's reasoning for turning it off is to save on electrical costs. This is why an energy efficient blower moter (low wattage) is the best! 

Is the HEPA Filter the Most Important Part of an Air Cleaner and are not ALL HEPA Air Cleaner Systems the Same?

NO , all HEPA Air Cleaners ARE NOT the same! Care must be taken when choosing a HEPA Air Cleaner because the most important part of any HEPA Air Cleaner, and the most expensive part besides the "True" HEPA air filter itself, is the Power, Performance and CFM (cubic feet per minute) of the Blower or Fan motor. There is no sense in having a good filter media such as a "True" HEPA filter if the blower or fan motor is weak and/or of poor quality. Since a "True" HEPA filter has a high efficiency of 99.97% a strong fan motor is REQUIRED and ESSENTIAL because the efficiency of any filter is meaningless if the unit can not draw air to and into the "True" HEPA filter itself.

Is a higher wattage unit mean stronger fan motor?

NO ! The higher the wattage simply means the higher in electrical costs to run. High quality and High-End HEPA air cleaning units do not use lower cost, high energy using fan motors. Energy efficient motors are available but at a higher cost to purchase. Also, most High Quality Fan Motors are also quieter! A portable HEPA Air Cleaner with a quality energy efficient fan motor should be in the area of 80 to 200 Watts MAX at 350 to 600 CFM.

The design of the air outlet on an air cleaner is also very important. The filtered air out of a unit should blow either downward, upward or only from one side away from the unit so the filtered air is'nt simple recycled and filtered again. Units that simply blow filtered air outward over the filter are least efficient because they filter more clean air than dirty air.

Because a "True" HEPA filter retains and filters out all particles from the air that passes through it down to0.3 microns in size at an efficiency rating of99.97% , ONLY  "True" HEPA filters are recommended by more Allergists and Doctors than any other filter type systems. ( EXAMPLE: If 6,000 air particles down to 0.3 microns (dust, etc..) are drawn through a "TRUE" HEPA Filter on a single pass, 5,998 of them would be captured and retained in the HEPA filter and only 2 particles would make it through! That's 99.97% efficiency... That's "TRUE HEPA!)

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