Why Air Purifier Experts Recommend HEPA Filtration
The use of HEPA filtration is recommended by many reputable organizations
for its effectiveness at removing lung-damaging particulates from the
air.The HEPA air filter is made from fine fibers that are
pressed together into a paper material, then pleated to provide the
largest surface area possible. HEPA filtration can remove from at
least 99.97% of dust, pollen, bacteria and airborne particles with a
size of 0.3 microns. The 99.97% specification is for particles exactly
0.3 microns in diameter because that is what’s known as the MPPS or
most penetrating particle size. Particles that are smaller or larger
are trapped with even higher efficiency. In other words 0.3 microns is
the worst case particle size and 99.97% is the worst case efficiency. HEPA
filters are composed of mat of randomly arranged borosilicate fibers.
The air space between the fibers is much greater than 0.3 microns. The
common assumption that a HEPA filter acts like a sieve where particles
smaller than the hole size get through is entirely incorrect. In a HEPA
filtration, particles are trapped by one of three mechanisms;
diffusion, interception or impaction. To begin with, the HEPA
filters fibers intercept the particles, impeding their straight
trajectory. Then impaction is applied, and those same fibers break the
flow of larger particles attempting to follow the airstream's natural
curve. Through this second step, the HEPA filter not only won't let
particles through, it also won't let them sneak around the bends. And
then, just to be certain, diffusion is introduced. Diffusion occurs
when a collision occurs between gas molecules and the very smallest
particles, cutting them off at the pass. With these three
incredibly effective facets of filtration, HEPA filters are able to
guarantee stopping 99.97% of all pollutants.
What leading authorities say about HEPA filtration:American
Lung Association: "A HEPA filter is the most efficient filter for
removing small particles which can be breathed deep into the lungs. In
most cases, these small particles are the ones that penetrate deep into
the lungs, causing health problems. Look for an air purifier with a
HEPA air filter that can effectively trap large and small particles,
including pollen, dust mites, pet hair and dander, and mold and mildew."Centers
for Disease Control and Prevention: "Portable HEPA air purifiers are
proven to be effective as a means of infection control in health care
environments. An air purifier HEPA filter will effectively reduce the
concentration of Aspergillus spores (which range from 1.5 um to 6 um)
to below measurable levels (100- 02). Therefore, HEPA filters can be
expected to remove infectious M tuberculosis droplet nuclei from
contaminated air." The U.S. Department of Homeland Security
"recommends the use of a portable HEPA air purifier to help trap
microscopic airborne contaminants, including biological agents that
could be released in a terrorist attack. Once trapped within a HEPA
filter, the contaminants are neutralized and prevented from entering
your body and making you sick. A HEPA filter is excellent at
eliminating dander, dust, molds, smoke, biological agents and other
contaminants." U.S. Environmental Protection Agency: "A HEPA
filter is best applied in situations where high collection efficiency
of submicron PM (particulate matter) is required, such as applications
involving chemical, biological, and radioactive PM. HEPA air cleaners
are recommended for the removal of indoor air pollutants, such as
pollen, mold, dust and other irritants that can aggravate respiratory
ailments." Dr. Philip M. Tierno, Jr., director of Clinical
Microbiology and Diagnostic Immunology at the Tisch Hospital, New York
University Medical Center and Mt. Sinai Medical Center: "Without
question, using an air purifier HEPA filter gives you an added degree
of security. HEPA filters are used in operating rooms, ICUs, and in a
wide variety of surgical areas to purify the air. An air purifier HEPA
filter is not only quick and effective, but it's relatively
inexpensive. When properly used, it's one of the best means of helping
to ensure good, quality air." Clifford W. Bassett, MD, a fellow
of the American Academy of Allergy & Immunology and director of
Allergy and Asthma Care of New York: "Over the last 10 years, the
incidents of allergy and asthma in children and adults have increased
tremendously. There are more than 57 million Americans now suffering
from varying degrees of respiratory problems. The use of an air
purifier HEPA filter as part of an overall plan to help maintain
cleaner air is highly recommended." Based on my consideration of
the facts, I believe that there is no higher, more effective, or cost
efficient method to choose from than HEPA filtration. For this reason
all of the air purifiers I feature on this site include HEPA filters. Return to Home Air Purifier Guide Homepage from HEPA Filtration article.
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