Failure to recognize when an aerosol isn't a droplet, but without the stubborn dissagreements. 7

[moon161]

For discussion of the primary matter of this thread, but the stubborn dissagreements can remain there.

https://www.eng-tips.com/viewthread.cfm?qid=483537

 

[RedSnake]

We hade a huge problem at our paint shop after someone else had taken over the running of the main building service.
They hade a lot of bad finish on the finished paint.
We use positiv and negative charge to get the paint to go to the "target".
After several month of investigations they reached the conclusion that the problem was that the building service department hade taken away all the humidifier from the ventilation system, so the air was full of all kind of particles when the air was dry, that was landing in the paint before it was dry.
And it might even be so that to dry air also effected the paints ability to find it's way to the "target" I think the paint is positively charged and the target negativ.
Not that would have any impact on a virus though.
So they hade to install new separate humidifiers there, with a control system keeping the humidity constant all the time.
I do not know at which level but I would guess around 45-50%.

And something totally of topic, I was looking for some info on this paint thing and found a promising link to a pdf.
And when I open it, it's a big picture on the frontpage with my CH.
It always hit you the hardest when you do not expect it, especially when he hated being photographed and I would never hade expected finding a photo of him on the web.

BR A


“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[zeusfaber]

Anna, What's "CH"? I understand who you're talking about - just don't recognise the abbreviation.

A.

 

[RedSnake]

It's the first two letters in his first name or the first of first name and first of his family name.
Ch. H he was always so private, I guess I still have it in me.
Even came across his Facebook page a couple of month back, almost never uses FB myself, you would not have know he was dead, that was also very strange.

This calculated evaporation curve might shead some light Fischstabchen it's not exactly the same conditions but it shows some interesting effects.

The relative humidity of the air is kept constant at 50%

How that is, can be read here.

https://www.ht.energy.lth.se/fileadmin/ht/Kurser/MVK160/2012/Holger.pdf

/A



“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[RedSnake]

I probably do not think that evaporation has much to do with the spread of the infection either.
If someone coughs or sneezes and there are drops of all possible sizes, those that are too large do not have time to get much smaller before they have fallen to the floor or some some other surface.
So only those with less than 100 microns can possibly fly around if that's the limit.
In that case, the question is whether they have time to be airborne for so long that they have time to be affected by evaporation before they get stuck on some solid object.
Ordinary solid particles or dust that are dry can be stirred up from draft and air movement even after landing on a surface.
Not sure that it applies for this Covid-19, I think that as long as it is most it can stay alive, when it dries out it dies.
And how much of what you cough sneeze or exhale is less than 100 microns if that's the limit?

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[Alistair_Heaton]

I have a gut feel that although crude my fart "taste test" is a reasonable indicator....

And the medic's I know who are mostly orthopaedic don't really have many arguments against that rule of thumb.

 

[waross]

I think that the point is first finding the source of the 5 micron limit, and once identified, trying to overcome the inertia to have the more realistic 100 micron limit accepted, and to have the protocols adjusted accordingly.
The science has been made pretty clear.
What is distressing is the refusal of so many people, both in the street and in medical administrative positions, to even consider that what they originally were taught was not a universal truth.
The reason for the 5 micron limit applys only to tuberculosis infection and not to aerosols/drops in general.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Alistair_Heaton]

Bill if you had ever done bioengineering you would understand the issue.

Medics hate engineers

I did FEA on hips and knees for a while and then got asked one day to go in and watch a spinal fusion implant because they kept on failing after 2 years, target 8-10.

I watched the surgeon cycle plastic bend a bit of titanium 4 times putting it into the neck. On the fourth bend I told him to scrap it.. All hell let loose, I said you can't do that with titanium... he said why not... physical properties its not aluminium. Give me a material that can... if I could the way you want to handle it I would get Nobel prize... How many times can I adjust it? 2 max... and that was the end of my bio engineering career.

 

[RedSnake]

Yes i think they changed there approach for Covid-19 just to be on the safe side.
Here they only went from 2 meter to 2,5 meter distance and forbid the use of table fans and fans in elderly homes to keep the heat away.
They still say they have not seen any real evidence of that this virus is what they call air born.
No spread have been detected in places where people are far apart but many visits every day, like shops and stores.
I think maybe the UK variant is a bit different it seems to spread easier.


Saliva contains of 95,5% water, and we know it's density, how much the virus weighs and how much heavier it can make a droplet or it's abelite to be air born is also a unknown.
After all it has one of the longest RNA strands they have seen.

Best Regards A




“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[FacEngrPE]

The 5 micron limit for TB probably has much to do with larger contaminated particles being filtered out rather well by mucus. Possibly mucus covered TB is not very infectious.

If it turns out that mucus covered covid is infectious, then the 5 micron to 100 micron particles are still in play even after they are captured by our natural mucus filtration. This might be related to "receptors" or the integrity of the package in mucus.

ACGIH is more about the entire system of things used to control workplace contaminates than just filtermasks.
[ul]
[li]Masks don't provide rated protection unless fit tested, and put on per the tested method. (each person needs their own fit test)[/li]
[li]Guiding the contaminate away from you is better than filtering it out at your nose.[/li]
[li]Control is easier at the source than using bulk space ventilation.[/li][/ul]

Masks have been found to be effective at controlling "sources" probably due to even poor filters being able to catch fresh wet sticky drops in a humid air stream easily.

 

[Alistair_Heaton]

I got TB as a kid by drinking unpasteurised milk...

I believe thats the main source in the UK of getting it.

Where I am now its public transport that its mostly traced back to.

Measles seems to be in the same city in a two day period and unvaccinated and if you get it they are not surprised even if there is no traceable contact.

 

[RedSnake]

Since one of the effects of the virus and they also know why it happens is that some looses there taste and smell.
So it infects the area in the nose where the smelling sensors are, so obviously it can sustain it self in that environment,
The most healthy and fit seems to have been getting it worse, getting infected in the lungs.
Here they have sade from the beginning that you couldn't get infected by eating something that hade it on it, never heard any one claim that it happened either.
The sickest person we hade, who survived was in intensive care sedated for three month, he was a firefighter.

/A


“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[RedSnake]

It only takes ten TBC bacteria to get infected,
In a single sneeze there can be 40,000 infectious droplets (0.5-5 µm in diameter).

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[TugboatEng]

That's why I think masks that are anything but 100% effective are useless for preventing infections. With viruses, technically it only takes one successful infection of a cell to cascade into illness. Obviously the odds are small but a mask that reduces droplets by 50% when there are tens of thousands and it only takes a few droplets to cause infection.

 

[Alistair_Heaton]

The mask is meant to catch those 40 000 droplets, its not meant stop you breathing it in.

 

[RedSnake]

Respirator Rating Letter Class
N - Not oil resistant
R - Resistant to oil
P - Oil Proof
Respirator Rating Number Class
95 - Removes 95% of all particles that are at least 0.3 microns in diameter
99 - Removes 99% of particles that are at least 0.3 microns in diameter
100 - Removes 99.97% of all particles that are 0.3 microns in diameter or larger. HE or HEPA quality filter.

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[dik]

I picked up 200 that were rated KN95 which I understand is similar to N95.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

The mask is meant to catch those 40 000 droplets, its not meant stop you breathing it in.

So, don't kiss someone wearing a mask...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[RedSnake]

Another difference between TBC and COvid-19 is that TBC is a bacteria it multiplies by dividing, it does not need get inside a cell to do it, and the immunsystem can't take care of it.
That's why it needs so few as ten to get infected.

If you got ten Covid-19 viruses in your mouth, nose or eyes, the chance of one making it to a cell to be able to reproduce is much smaller I would think.

/A



“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[TugboatEng]

It only takes one virus to infect a cell. That cell then replicates the virus until it bursts releasing 50,000 viruses.

http://book.bionumbers.org/how-many-virions-result-from-a-single-viral-infection/

 

[electricpete]

That's why I think masks that are anything but 100% effective are useless for preventing infections. With viruses, technically it only takes one successful infection of a cell to cascade into illness. Obviously the odds are small but a mask that reduces droplets by 50% when there are tens of thousands and it only takes a few droplets to cause infection.

So the only choices are 100% effective or completely useless?!?
I see you brought your typical level of nuance to the subject!!!

Let’s say every inhaled virus particle has 0.001 probability of infecting you.
Then probably of not getting infected by one inhaled virus particle is 0.999
If you inhale N particles during a given interaction (N is proportional to product of inhalation concentration and staytime) then the probability of not getting infected during that interaction is 0.999^N (to not get infect after N particles, then each must not infect you, and we assume non-infection probabilities are independent).

So:
P(not getting infected)= 0.999^N
P(getting infected) = 1 -P(not getting infected) = 1 - 0.999^N
Plot this curve vs N below. Notice the following:
[ul]
[li]For N < 500 it is a very linear increase. 50% reduction in concentration can decrease your risk by almost 50% in this region. Our risk reduction is comparable to the minimum filtering efficiency of our mask [/li]
[li]For N > 5,000, the probability of getting infected approaches 1 constant, so a low rate of increase. You are almost certain to get infected and 50% reduction in concentration probably won't help much in this region[/li]
[/ul]

So whether a given intervention that reduces N by 50% is worthwhile during a given interaction depends to some extent on where N starts out on that curve.
I saw a paper that drew such curve (can’t find the link) and made the case that we are in the linear part of the curve in the vast majority of interactions (there are very few interactions where you are almost guaranteed to catch the virus with near 100% probability). Here's my example curve using my arbitary 0.999 number, I don't recall the numbers in the paper. Also you might consider N as either virions or virus-laden respiratory particles, each requires some assumptions especially in the independence.

=====================================
(2B)+(2B)' ?