ovrszd
Epic Contributor
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There seem to have been a couple of questions recently about why health officials are saying N95 masks aren't necessary. I don't know if this has been answered or not, but here goes:
An N95 mask blocks 95% of all particles that are 0.3 microns (10^-6 m) or larger. However, virus-laden droplets are produced when you talk, breathe, cough, and sneeze. The size distribution of these droplets are well established. Sneezing produces "large" droplets, around 100 micron and higher. Coughing, speaking, and breathing create droplets in the range of 1-100 micron, with a concentrated peak around 5 micron.
Now, at first blush, it may seem like the masks will do a good job, therefore, of filtering out these droplets. The actual answer, is yes and no. As droplets enter the air, depending upon the relative humidity of the surroundings, they can quickly (a matter of seconds) evaporate down to sub micron levels. Most viruses are on the order of nanometers (10^-9 m) in size. So, one small submicron fluid droplet can have many viruses suspended inside. These smaller droplets are what cause the concern. Larger droplets quickly fall to the floor due to their sedimentation velocity and pose little risk unless someone coughs or sneezes directly onto you. Smaller droplets (submicron) can stay suspended in the air for multiple hours. Recent research has also shown that Coranaviruses can stay viable (alive) in droplets in the air for 30 minutes - 3 hours. This is one of the biggest concerns for transmission. These smaller droplets are much smaller than 0.3 micron, so even with a perfectly fitted respirator/mask, it is useless to keep you from breathing these smaller particles. This is why the 6 foot rule is in place. It is believed that 6 feet will provide a large enough distance that even when these droplets are dispersed into the surroundings, the concentration will be so low due to mixing with the surrounding air that the risk of infection is greatly reduced.
However, if YOU are sick a mask will prevent you from dispelling infected droplets. Remember, the masks filter 95% of anything larger than 0.3 microns, and the droplets coming out of your mouth are almost universally greater than 1 micron, as there isn't time for them to evaporate before they hit the mask/filter. So, if you think you may be sick, or are worried about possibly infecting someone else, definitely DO wear a mask.
So, the efficacy of a mask is not in protecting yourself, but in protecting others. So, wearing it yourself does very little. But, if everyone else wears one, YOU will be protected.
Very well explained!!!!
My primary concern is not getting infected, that is secondary. My primary concern is not infecting someone else.