Mountaineer wrote: ↑Tue Oct 06, 2020 3:06 pm
doodle wrote: ↑Tue Oct 06, 2020 11:07 am
WiseOne wrote: ↑Tue Oct 06, 2020 10:56 am
Science sucks sometimes, doesn't it doodle? Annoying when it produces results that contradict your beliefs. I understand how upsetting that can be.
Read the document.
I don't have time now spent 10 minutes...but the gist is clear. Marginal benefit..if at all. I also realize that scientific studies are based on observing outcomes of human behavior and many humans are idiots. For example, just because an amazon review says something doesn't work doesn't mean the product is at fault...could be the user is a moron. If n95 masks filter virus particles then employed correctly I don't see how they could not work. Although, I don't understand how social distancing and quarantine wouldn't work as they eliminate route of transmission. If you had a virus such as I hypothesized, if you quarantined everyone in house or at least within city (shutting down all transportation) the virus couldn't spread and would die. How would you address such a virus? It does operate according to mechanisms.
Re. mask effectiveness: I am almost completely speculating on my comments below, others more knowledgable than I am please chime in.
From what I've read, masks reduce spread of droplets, let's say above 3 microns. Also from what I've read, the virus (consisting of RNA, not even a living organism I believe, but has the ability to invade a cell and replicate) is something like 0.25 microns in size. Let's say that the N95 mask stops transmission of 95% of the droplets 3 microns and up with their associated viral bits inside the droplet; the viral bits outside the droplets or in droplets smaller than 3 microns go right through. Make your own guess about the number of virus particles an infected person exhales, and the number required to cause someone downstream to get sick. I am sure the N95 will stop my first exhaled 3 micron up droplets. Not so sure about those from the subsequent exhales as the mask gets wetter and wetter from my exhales. I would think that at some point, probably a few minutes, the mask will no longer effectively stop 95% of 3 micron and up droplets, let alone 0.25 micron virus particles. Thus, masks probably don't work much after the first few minutes of putting them on. Obviously, this is dependent on the surrounding humidity and air currents as to how much of the viral load gets released past the N95 mask, but I'm speculating that it is quite enough to get someone downstream sick if they are in the susceptible category. I'm also speculating that the RNA viral particles last more than a few minutes in air. Lots of speculation but I can see how masks have limited effectiveness on keeping us safe and healthy. Not zero, but very limited. I've seen those videos of masks stopping sneezes and such but I've not seen test results of new vs used masks in those videos or any data associated with those type of tests. Perhaps they are out there somewhere, as Fox Mulder might say.
The COVID-19 particle is indeed around 0.1 microns in size, but it is always bonded to something larger.
As many states and communities ease restrictions related to the COVID-19 pandemic, the debate over mask usage has intensified.
Businesses, churches and governments have implemented all manner of policies — some requiring masks, some leaving it up to each person, some even banning masks. And that has spurred many armchair epidemiologists to weigh in, including a Facebook page with nearly 1 million followers.
A June 4 post from Why don’t you try this? went a step beyond the homemade mask debate to claim that even the N95 masks used by health care workers are pointless in the face of COVID-19.
“COVID 19 virus particle size is 125 nanometers (0.125 microns); the range is 0.06 microns to .14 microns,” the post said. “The N95 mask filters down to 0.3 microns. So, N95 masks block few, if any, virions (virus particles).”
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.
But that’s not the only logical flaw in this claim.
The N95 filter indeed is physically around the 0.3 micron size. But that doesn’t mean it can only stop particles larger than that. The masks are actually best for particles either larger or smaller than that 0.3 micron threshold.
“N95 have the worst filtration efficiency for particles around 0.3,” Marr said. “If you’re smaller than that those are actually collected even better. It’s counterintuitive because masks do not work like sieving out larger particles. It’s not like pasta in a colander, and small ones don’t get through.”
N95 masks actually have that name because they are 95% efficient at stopping particles in their least efficient particle size range — in this case those around 0.3 microns.
Why do they work better for smaller ones? There are a number of factors at play, but here are two main ones noted by experts:
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.
“Although these particles are smaller than the pores, they can be pulled over by the charged fibers and get stuck,” said Professor Jiaxing Huang, a materials scientist at Northwestern University working to develop a new type of medical face mask. “When the charges are dissipated during usage or storage, the capability of stopping virus-sized particles diminishes. This is the main reason of not recommending the reuse of N95 masks."
