Re:Why Asians wear surgical masks in public (2014)
by rjf72 on Monday March 18, 2019 @04:35AM
(#19419479)
This is commonly stated, but untrue. Here are a couple of studies on this topic. [1] [2] And the always critical third link. [3]
The nature study carried out specific tests and indeed surgical masks did surprisingly very well at blocking particulate matter all the way down to 1 micrometer, with a significant effect on much smaller particles as well. PM2.5 = 2.5 micrometer / 2500 nanometers. The NIH study compared the health effects of individuals with/without masks in everyday activity in Beijing.
I think the assumption is that if the particulate matter is smaller than the size of the 'gaps' within a mask then it would be ineffective. I always just visualize a simple experiment. Imagine shooting a stream of particles of a given size at a wall. Now interject a 'net' of practically any size. Now interject multiple 'nets' (as is the case in typical surgical masks). It becomes clear that even quite large large filters will have a non-zero effect on stopping matter far smaller than the max size that can make it through.
The nature study carried out specific tests and indeed surgical masks did surprisingly very well at blocking particulate matter all the way down to 1 micrometer, with a significant effect on much smaller particles as well. PM2.5 = 2.5 micrometer / 2500 nanometers. The NIH study compared the health effects of individuals with/without masks in everyday activity in Beijing.
I think the assumption is that if the particulate matter is smaller than the size of the 'gaps' within a mask then it would be ineffective. I always just visualize a simple experiment. Imagine shooting a stream of particles of a given size at a wall. Now interject a 'net' of practically any size. Now interject multiple 'nets' (as is the case in typical surgical masks). It becomes clear that even quite large large filters will have a non-zero effect on stopping matter far smaller than the max size that can make it through.
[1] - https://www.nature.com/articles/jes201642
[2] - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2662779/
[3] - https://sci-hub.tw/