What exactly is HEPA and its use in Air Purifiers?
First things first. HEPA is not a brand or technology. HEPA is a standard. Any mechanical air filter that meets the specified standard can be termed as a HEPA Filter.
What is the standard? The air filter should be able to remove up to 99.97% .3 micron size particles from the air. If HEPA was a basketball player then he would basket the ball 9977 times every 10,000 shots she/he was given – :). At the same time it means that smaller particles are also removed but at a lesser percentage level. Air is pushed against the HEPA filters that capture dust and other contaminants. As a result, there are no side effects of using HEPA filters and are pretty safe to use for allergy and asthma patients. If its genuine HEPA filter, then it will trap mold spores, bacteria and even viruses. HEPA filters may be marketed as True HEPA or Absolute HEPA. “Hepa-Types” or “HEPA likes” generally do not meet the HEPA standards. If HEPA filter has number quoted (99.97% / .3 micron), then generally it’s the right HEPA filter. What’s this buzz about .3 micron particles? – To put this in perspective, the size of this .3 micron particles is approximately 300 times less human hair’s diameter. Human eyes starts seeing particles that 75 to 150 times larger than .3 microns. Good eyesight test but we are not sure how to test your eyesight using this technique :).
While Wars are a curse but one side effect of war times is inventions. HEPA filter is no different and its first recorded use was for the Manhattan project – A project that drove development of atomic bombs: those dropped over Hiroshima and Nagasaki in Japan.
HEPA filters are good for home use. For industrial strength, there are ULPA filter. HEPA filters are commonly used in conjunction with Activated Carbon Filters that enable flushing out gases and odors since HEPA filters will pass the gaseous air.
One good thing about HEPA filter which is totally counter intuitive. We would think that as the HEPA filter gets dirty, the filters efficiency would decrease. But it’s exactly the opposite way round! The dirtier the HEPA filter, the better it cleans! Wow, your wife would not complain about one dirty thing in the house! Well keep in mind though. Too dirty HEPA filter can become a fertile breeding ground for microbes. Also, too dirty filter will avoid the air flow.
What are HEPA filter made of? HEPA filters are made from a fabric of intertwined and jumbled fibers. The fibers are put together in a random pattern to form a jumbled up pattern. The air passes through this maze and undergoes impact, sieving, interception and diffusion.
What a HEPA filter won’t do? A HEPA filter will not clean up smells, odors and VOC’s (Volatile Organic Compounds). That is the reason that air purifiers use other combination of technologies such as Activated Carbon filter along with HEPA Filters.
And Yes, By The Way HEPA stands for “High Efficiency Particulate Air” or “High Efficiency Particulate Arrestance.”