Why Air Purifier Experts Recommend HEPA Filtration

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:

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.