Viruses and Bacteria
The name "coronavirus" derives from the Latin corona, meaning crown, because the virus envelopes appear to be "crowned" by a ring of small, bulb-like structures as seen in electron microscopy.
BFE - BACTERIAL FILTRATION EFFICIENCY
Viruses are generally smaller than bacteria and the vast majority pass through microbial filters that trap bacteria. Virus size is measured in nanometers while EN 14683 standard applies to bacterial filtration efficiency with regard to 2,5 micron size.
The virus particle diameter is 70-100 nm. One nanometer is one billionth of a meter, or one millionth of a millimeter. So one nanometer equals 10−9 m.
1 nm = 0,001 μm = 0,000 000 001 m = 10−9 m