What is a HEPA Filter and how it works?
HEPA stands for High Efficiency Particulate Arrestance. Invented by the military back in the fourties it was used to filter out radioactive dust and biological contaminants from the air .
What’s the deal with 0.3 micron or less? Does an hepa filter capable to reduce particulates smaller than that?
Yes of course, only at a different extent. But first lets define 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.
Now, an hepa filter that is certified to filter out 99.97% of particles at 0.3 micron it is also capable to filter out smaller ones with an efficiency less that 99% efficiency.