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Writer says masks are useless if they do not have proper filtering

To the Editor:
The size of the coronavirus is reported to be between 26 and 32 kilo bases. Kilo base is a unit of measurement used in molecular biology equal to 1,000 base pairs of DNA and RNA. To get to more familiar units first note that 10 base pairs is a distance of 34 angstroms (light measurement). Thus a kilo base is 3,400 angstroms. Thus the coronavirus is between 26 X 3,400 = 88,400 angstroms and 108,800 angstroms. Since 1 millimeter is 1×107 angstroms then the coronavirus is from 0.0088 to 0.01088 mm or 0.00035 to 0.00043 inches. Or it is between 8.8 and 10.88 microns? Note that dust particles are between 2.5 and 10 microns.
This means for any mask to be effective it must be capable of filtering out particles less than 8 microns plus the mask must be sealed against the face including the nose. If a mask does not state what size particles it will filter out you have no guarantee that it will prevent transmission of the coronavirus. A mask that has a NIOSH filter approval rating of N95 (P95) or higher will filter out the coronavirus. However, when an infected person coughs or sneezes he emits aerosol droplets that are much larger than the coronavirus itself. These larger droplets may contain numerous coronaviruses. Thus masks that will not stop a single coronavirus can stop the aerosol droplets and thus accord a certain level of protection but again the mask must fit snugly against your face. That is why a mask of any type when you are in a large group of people or in a large store does afford some level of protection. But if you want full mask protection it must meet the NIOSH 95 rating. Thus when politicians state that everyone must wear some type of a mask (not certified) they are giving people a false sense of security. Staying away from crowded areas, using social distancing and washing your hands are probably the best things you can do.
Of course you should at least temporarily stay away from any area where an outbreak is reported. If you have coronavirus symptoms or any other virus or cold symptoms then wearing a mask of any type will help stop you from spreading the problems to others.  That is perhaps the biggest benefit of wearing any mask.
Relative to masks I have looked at numerous ones presently available in our area but none of them reference a NIOSH rating. The only one that is occasionally available in local stores is the 3M COOL FLOW RESPIRATOR 8511 that has an N95 rating. Based on what is stated above it would be ridiculous to have school children all wear masks. They are just not that effective. With the present situation, the most effective thing that can be done is check the temperature of all teachers and personnel then check the temperature of every student each morning. Those having a temperature should not be allowed in the school and should be sent to a doctor then home or to a hospital. If anyone has a temperature their blood oxygen level should be checked to see if they need to immediately go to a hospital.
It might be worthwhile to consider using the temperature test procedure during any future virus/flu season. This might prevent a complete school or school system from being closed temporarily due to a larger number of cases by keeping infected persons away from the school before large scale transmissions occur. This would prevent the large scale interruptions that have occurred in the past.
As always the best thing you can do is build up your immune system by using  supplements such as vitamins C, D, A, selenium, E and zinc.
J. Ronald Winter