Coronavirus and homemade tools

[Crusty]

The major usage for N95 masks (the surgical standard) is not to block pathogens coming in but rather to protect others from pathogens going out which might be inadvertently expelled by the wearer. The masks are intended to potentially protect others from aerosolized pathogens. Wearing one's a caring and responsible thing to do but not very effective at blocking an incoming infection.

[Jon]

The major usage for N95 masks (the surgical standard) is not to block pathogens coming in but rather to protect others from pathogens going out which might be inadvertently expelled by the wearer. The masks are intended to potentially protect others from aerosolized pathogens. Wearing one's a caring and responsible thing to do but not very effective at blocking an incoming infection.

This is a valid point, but note that, yes, this is true for surgical masks, aka "procedure masks", but N95 masks are also worn to protect healthy people.

Unfortunately, because covid infected people can be asymptomatic and contagious for - what we now believe - to be a median of 5 days, if we encourage widespread mask-wearing, then people who are unknowingly ill but feel healthy will not be transmitting the virus.

Reusable respirators with P100 filters will filter even more than N95s, and lots of our guys will have those in their shops already. 3M actually manufactures a P100 filter that is specifically designed for viral outbreaks. PDF is here. A single pair of filters is expected to last for a full pandemic wave. Note the 6035 filter model number; I believe this is a 7093 model in the US market - good luck finding any of those now! However, any P100 filter will work, and the plastic encapsulated ones can be removed, wiped down, and then the respirator can be submerged to be sterilized.

[Saltfever]

. . . 3M actually manufactures a P100 filter that is specifically designed for viral outbreaks. PDF is here.

Another PDF here for your viewing pleasure. Remember, "PN" is the filter efficiency in trapping particles equal to or GREATER than 0.3 microns. Anything smaller might get through depending on the entrapment scheme used by the manufacturer.

Of the more than 5,000 known viruses only a few are larger than 0.25 micron. Covid-19 is spherical and about 125nm in diameter (Wikipedia). It seems PN95 to PN100 work fairly well. Information is offered here so those who are thinking of home-brew solutions know the difficulty of the problem. How do you effectively trap a 0.125 micron diameter particle?