HEPA is an acronym for “High Efficiency Particulate Arresting”
or “High Efficiency Particulate Air”
HEPA air cleaner can remove from the air at least 99.97% of dust,
pollen, bacteria and any airborne particles with a size of 0.3 micrometers. The
99.97% specification is for particles exactly 0.3 micrometers 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 micrometers is the most case particle size and 99.97% is the
worst case efficiency.
HEPA filters are composed of mat of fibers. The air space
between the fibers is much greater than 0.3micrometers. The common assumption
that a HEPA filter acts like a sieve where particles smaller than the hole size
get through is entirely incorrect (membrane fibers work that way).
In a HEPA
filter, particles are trapped (which stick to a fiber) by one of three
mechanisms; diffusion, interception or impaction.
The original HEPA filter was designed in the 1940s for and
used in the Manhattan Project to prevent the spread of airborne radioactive
contaminants. It was commercialized in the 1950s and the original term became a
registered trademark and a generic term for highly efficient filters.
decades, filters have evolved to satisfy the higher and higher demands for air
quality in various high technology industries such as aerospace, pharmaceutical
processing and electric micro circuitry (computer chips).
Today, a HEPA filter
can be any highly efficient air filter that can attain the same filter
efficiency performance standards of at least 99.97% and 0.3 micrometers or
**Note: A HEPA filter alone does not kill airborne
Viruses, Bacteria, Mold, and Fungi
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