Hopefully this makes more sense to people. It's in poor taste to snarf an entire article - but I've posted a lot of it because I know most people don't click through.
In other words, the post asserts the virus is smaller than the filter on the N95 mask, so the N95 mask doesn’t work.
Experts say this claim flies in the face of numerous studies and reflects a failure to grasp fundamental principles of how viruses behave and how face masks work.
Virus particles don’t exist alone The science of mask functionality gets really small, really fast. The unit of measurement here is microns — 1/1000th of a millimeter.
The size-based argument against N95 laid out in this claim assumes mask filtering works something like water flowing through a net — particles in the water smaller than the net opening pass through, while larger items don’t.
But the physics involved don’t work like that at all.
The COVID-19 particle is indeed around 0.1 microns in size, but it is always bonded to something larger.
“There is never a naked virus floating in the air or released by people,” said Linsey Marr, a professor of civil and environmental engineering at Virginia Tech who specializes in airborne transmission of viruses.
The virus attaches to water droplets or aerosols (i.e. really small droplets) that are generated by breathing, talking, coughing, etc. These consist of water, mucus protein and other biological material and are all larger than 1 micron.
“Breathing and talking generate particles around 1 micron in size, which will be collected by N95 respirator filters with very high efficiency,” said Lisa Brosseau, a retired professor of environmental and occupational health sciences who spent her career researching respiratory protection.
Health care precautions for COVID-19 are built around stopping the droplets, since “there’s not a lot of evidence for aerosol spread of COVID-19,” said Patrick Remington, a former CDC epidemiologist and director of the Preventive Medicine Residency Program at the University of Wisconsin-Madison.
The article goes on to say:
The first is something called “Brownian motion,” the name given to a physical phenomenon in which particles smaller than 0.3 microns move in an erratic, zig-zagging kind of motion. This motion greatly increases the chance they will be snared by the mask fibers.
Secondly, the N95 mask itself uses electrostatic absorption, meaning particles are drawn to the fiber and trapped, instead of just passing through.
Put on a mask when it's freezing outside and breathe. Then tell me that millions of water droplets aren't coming through it.
ReplyDeleteEasy physics always sounds like this.
ReplyDeleteBrownian motion as a complete explanation does not apply to situations where there is a continuously variable force (such as suction) that moves the particles at greater force.
Electrostatic principles also do not apply when the mask material may be compromised by larger particles being forced through the mask (again by suction), creating gaps for the passage of smaller particles.
Things I wouldn't consider an N95 mask adequate for: ricin (2^-2 molecular mass), norovirus (same power of 2 molecular mass), airborne aerosols of HIV (roughly the same molecular size with greater mass).
But for shits and giggles, put a small amount of methyl ethyl ketone in a space where you're doing some sanding and see how quickly through a respirator mask it'll be overpoweringly strong.
Also, I totally trust those civil and environmental people when it comes to materials engineering, yup, totally.
There's also not much evidence for something when you're not looking for it in conditions that replicate all of the factors involved.
Now if you add some discussions about frictionless surfaces, how there's no such thing as centrifugal force (despite the Earth being in a rotational system that produces them), and so on, we'd have all of the makings of really crap college physics! :-)