Originally Posted By: KenK

I'll have to admit that I don't understand why 95% filtering efficiency is considered sufficient protection against the virus. Maybe it's like drinking water cleanliness. The body can fight just a few nasties (such as 5%), but not when too many nasties are injected (or inhaled). If so. I suppose the choice of N95 vs. N99 depends upon the nasty involved.

OR, is it that the ~5 micron COVID-19 aerosol droplet is big enough that the N95 respirator is much more efficient than 95% for the COVID-19 aerosol droplet??


N95 Respirators. An N95 respirator is a respiratory protective device designed to achieve a very close facial fit and very efficient filtration of airborne particles. The 'N95' designation means that when subjected to careful testing, the respirator blocks at least 95 percent of very small (0.3 micron) test particles.

All the ppe devices are compromises of some sort, designed to encourage compliance by health care workers. l The finer the filter, the more energy it takes to inspire air through it. When hcw are really serious about airborne pathogens and droplets and stuff, they wear the blue suits, helmets and hepa filtered powered air supplies like the ones in the movies, or the CBW oufits the military wears.
Health care costs a lot, and the system is mostly private, and the pressure to cut costs has encouraged reduction of excess capacity and lowest bidder, just-in-time logistic solutions. So the health care delivery system isn't generally prepared for what is happening. Hence the CDC bandanna/face shield recommendation: the face shield will keep off the big droplets, the bandanna will perhaps slow down the rest.

and yes, this is all about viral load.
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