Elevators and airflow

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anorlunda
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Elevators are a problem in this post COVID world. It is impossible to maintain social distancing while also meeting the passengers-per-hour needs of the building. Skyscrapers without efficient elevators are not practical.

The new social etiquette says that it is OK to shut the door of the elevator in the face of another person trying to get on, but probably not OK to use pepper spray to keep others off. :wink:

News reports say that some residents are leaving New York City permanently. Should we expect a reversal in the trend toward high density living to be a consequence of this pandemic?
 
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bob012345
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Elevators are a problem in this post COVID world. It is impossible to maintain social distancing while also meeting the passengers-per-hour needs of the building. Skyscrapers without efficient elevators are not practical.

The new social etiquette says that it is OK to shut the door of the elevator in the face of another person trying to get on, but probably not OK to use pepper spray to keep others off. :wink:

News reports say that some residents are leaving New York City permanently. Should we expect a reversal in the trend toward high density living to be a consequence of this pandemic?
Elevators don't have to be a problem at all. I believe effective isolation of people relatively closely spaced can be achieved with proper air flow engineering. So-called air curtains are already used in many industrial, commercial and medical settings to manage temperature differences, particles and biohazards. Filtered air comes from the top and breath would be directed downwards through the floor and filtered.

https://jamanetwork.com/journals/jama/article-abstract/343288
https://www.marsair.com/air-curtains-101
 
  • #3
anorlunda
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Elevators don't have to be a problem at all.
You mean modern elevators equipped as you said.


Another novel idea I saw in elevator discussions is to require silence (no talking). It sounds crazy but it would cut down on droplets sprayed. Others before have suggested that singing by church choirs and the loud speech habit said of New Yorkers have contributed to hotspots.

AFAIK it would be unprecedented to forbid talking in public, but it might be logical at this point in time.
 
  • #4
bob012345
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AFAIK it would be unprecedented to forbid talking in public, but it might be logical at this point in time.
Great Idea. Let's start with politicians....
 
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  • #5
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Elevators don't have to be a problem at all. I believe effective isolation of people relatively closely spaced can be achieved with proper air flow engineering. So-called air curtains are already used in many industrial, commercial and medical settings to manage temperature differences, particles and biohazards. Filtered air comes from the top and breath would be directed downwards through the floor and filtered.
  • Who is going to install that in every elevator now?
  • It might reduce the risk a bit (do you have numbers?) but it can't prevent droplets from reaching others
Another novel idea I saw in elevator discussions is to require silence (no talking). It sounds crazy but it would cut down on droplets sprayed. Others before have suggested that singing by church choirs and the loud speech habit said of New Yorkers have contributed to hotspots.

AFAIK it would be unprecedented to forbid talking in public, but it might be logical at this point in time.
It's probably really difficult to impossible to require that, but making a suggestion to not talk in elevators when others are present would be a possible step.
 
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bob012345
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  • Who is going to install that in every elevator now?
  • It might reduce the risk a bit (do you have numbers?) but it can't prevent droplets from reaching others
Air curtains certainly could prevent droplets from spreading. The momentum of moving air can sweep them down faster than they are moving forward in the breath. As far as who's going to install them now? The point is that technologies exist that can make the post-pandemic world a lot safer in general and better able to handle future pandemics without drastic shutdowns.
 
  • #7
atyy
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There has probably been COVID-19 transmission in elevators.
https://www.donga.com/en/article/al...e-of-COVID-19-transmission-inside-an-elevator

But a case study from Korea suggests that if precautions are in place, elevators can be safe to use.
https://wwwnc.cdc.gov/eid/article/26/8/20-1274_article
"Despite considerable interaction between workers on different floors of building X in the elevators and lobby, spread of COVID-19 was limited almost exclusively to the 11th floor, which indicates that the duration of interaction (or contact) was likely the main facilitator for further spreading of SARS-CoV-2."

In some buildings in Korea, these precautions include a recommendation of minimal talking in elevators, as @anorlunda suggested. The article also shows a picture of an elevator in Germany with signs on the floor indicating the safe distance.
https://www.citylab.com/transportat...ronavirus-health-risks-design-history/611032/

Another article about how to ensure safe distancing, among other measures, in elevators
https://qz.com/work/1853592/salesforce-will-reopen-in-seoul-with-tickets-for-elevators/
 
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Air curtains certainly could prevent droplets from spreading. The momentum of moving air can sweep them down faster than they are moving forward in the breath.
I would like to see a reference for that claim.
As far as who's going to install them now? The point is that technologies exist that can make the post-pandemic world a lot safer in general and better able to handle future pandemics without drastic shutdowns.
The cost/benefit of that specific action is questionable.
 
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  • #9
anorlunda
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In some buildings in Korea, these precautions include a recommendation of minimal talking in elevators, as @anorlunda suggested. The article also shows a picture of an elevator in Germany with signs on the floor indicating the safe distance.
https://www.citylab.com/transportat...ronavirus-health-risks-design-history/611032/
The point is that if you increase public distancing in public transportation (elevators, buses, subways, trains, airplanes), you reduce its capacity. So when the lockdown ends, there will be reduced capacity to get people to/from work.

Facebook said that some workers can work at home permanently.
https://www.nytimes.com/2020/05/21/technology/facebook-remote-work-coronavirus.html
PF members from other countries may not be aware of the severe housing shortages and very high housing prices near Silicon Valley in California.

Working from home permanently, frees up the employee to live anywhere. He/she does not need to live near the employer, no need to live in a city at all. He/she can choose to live where it is most pleasant and affordable, including other countries.

This crisis may be the trigger of many social changes. Not necessarily the entire cause but the trigger.

Scenes like this one may be gone forever.
Subway-Crammer.jpg
 
  • #10
Vanadium 50
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Elevators are a problem in this post COVID world.
Why? Specifically, why post-covid? Pre-covid, respiratory diseases killed about 400,000 people per decade; including covid, it's 500,000. It's hard to logically conclude that a risk of x is perfectly acceptable but a risk of 1.25x requires massive changes.

It's measurably true that population density makes things worse, and I am certain that elevators are a part of this. Maybe a large part. It's also measurably true that public transportation in general (think of elevators as a special case) makes things worse. But these statements are just as true for annual flu.

(I'm sure some busybody will be arguing that taking the stairs is good for people - ban elevators!)
 
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  • #11
wukunlin
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(I'm sure some busybody will be arguing that taking the stairs is good for people - ban elevators!)
Heh, I used to work for a company that uses that argument to disallow all staff except for the most senior managers from using elevators in the office.
 
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bob012345
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I would like to see a reference for that claim.The cost/benefit of that specific action is questionable.
No one has specifically designed air curtains for elevators as far as I know because pandemics were just not a design consideration until now. So I can't give you a detailed proof but other applications have included medical grade isolation* and the concept is clear enough to model. Unless you believe that the Corona virus is immune to being carried away by a moving air mass, it should work. However, here is a new device which applies the concept for protection on a personal basis;

https://www.timesofisrael.com/haifa...designed-face-covering-for-treating-covid-19/

*https://jamanetwork.com/journals/jama/article-abstract/343288

https://www.marsair.com/air-curtains-101

Regarding the cost/benefit, with 30+ million Americans unemployed right now, it's highly likely that new industries and many devices and concepts will be created to make the new normal safer. I don't think we should start throwing away ideas just yet. Of course, it's possible that in six months or a year, the pandemic and its concerns will fade away and people will get cheap and not prepare for the next round.
 
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anorlunda
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No one has specifically designed air curtains for elevators as far as I know because pandemics were just not a design consideration until now. So I can't give you a detailed proof but other applications have included medical grade isolation
The doubtful part is that it can work with such close spacing. Those people are nearly in kissing range.

1590521867872.png
 
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  • #15
Vanadium 50
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The risks don't change, society does.
Well, maybe. There definitely is a sense of "dying of covid is worse than dying of anything else going around" and that will tend to make people more risk-averse. On the other hand, if people get too risk averse they move away. Elevator upgrades depend on a Goldilocks principle.
 
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  • #16
bob012345
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The doubtful part is that it can work with such close spacing. Those people are nearly in kissing range.

View attachment 263535
Imagine a warm, gentle 10-12 mph uniform breeze of clean filtered air coming down from the top. The riders will draw in fresh air and their exhaled breath will move down very quickly and be filtered and either recycled or ejected. But if you're worried about a bad hair day, take the stairs. Of course, the concept would have to be designed and modeled. Here is a visualization of a related concept, a microbiological safety cabinet.

 
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BillTre
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Imagine a warm, gentle 10-12 mph uniform breeze of clean filtered air coming down from the top. The riders will draw in fresh air and their exhaled breath will move down very quickly and be filtered and either recycled or ejected.
This sounds like a downflow or downdraft set-up like used by some wood workers to control dust, rather than a air curtain.

I conceive of an air curtain as an area of rapidly moving air which prevents other air currents passing through the area perpendicular to its flow.
I don't think this would work on a crowded elevator. There would have to be air-curtains between each individual.

A laminar flow hoods are a different thing. They can be set-up for keeping bad stuff in or keeping bad stuff out depending upon your purpose. Their air flow mechanisms can be complex and their flows can be easily disrupted momentarily, as the video you posted shows.

To me, the downflow situation would seem to be the most promising for crowded elevators. It's function would be the least disrupted by randomly located people and their movements.
I expect that just having fewer people in a well ventilated elevator might be just as effective.
 
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  • #18
bob012345
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This sounds like a downflow or downdraft set-up like used by some wood workers to control dust, rather than a air curtain.

I conceive of an air curtain as an area of rapidly moving air which prevents other air currents passing through the area perpendicular to its flow.
I don't think this would work on a crowded elevator. There would have to be air-curtains between each individual.

A laminar flow hoods are a different thing. They can be set-up for keeping bad stuff in or keeping bad stuff out depending upon your purpose. Their air flow mechanisms can be complex and their flows can be easily disrupted momentarily, as the video you posted shows.

To me, the downflow situation would seem to be the most promising for crowded elevators. It's function would be the least disrupted by randomly located people and their movements.
I expect that just having fewer people in a well ventilated elevator might be just as effective.
Downflow may be a better term actually but I got the concept from the air curtain and it has the same goal which is to separate each rider from the others. Again, the Bio hood was just to point out the benefits of forced air movement but it does separate the hazards from the person and from the other hazards. A different application of the same principle.

I doubt just having fewer people would be as effective. I think we all just weren't sensitive to how far just breathing can carry a virus. In an elevator everyone is basically breathing in everyone else's breath. Of course with masks that will be mitigated somewhat.
 
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No one has specifically designed air curtains for elevators as far as I know because pandemics were just not a design consideration until now. So I can't give you a detailed proof but other applications have included medical grade isolation* and the concept is clear enough to model. Unless you believe that the Corona virus is immune to being carried away by a moving air mass, it should work. However, here is a new device which applies the concept for protection on a personal basis;

https://www.timesofisrael.com/haifa...designed-face-covering-for-treating-covid-19/

*https://jamanetwork.com/journals/jama/article-abstract/343288

https://www.marsair.com/air-curtains-101
None of these are anywhere close to the situation in an elevator. So let me write this explicitly: You don't have any reference supporting any benefit in an elevator.
Regarding the cost/benefit, with 30+ million Americans unemployed right now, it's highly likely that new industries and many devices and concepts will be created to make the new normal safer. I don't think we should start throwing away ideas just yet. Of course, it's possible that in six months or a year, the pandemic and its concerns will fade away and people will get cheap and not prepare for the next round.
Your answer to a cost/benefit question is to highlight that it will employ more people, which means it will cost a lot?
 
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  • #21
Klystron
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As a tech note: air curtain technology has been in widespread use for many decades where I live in the desert usually to separate areas with different temperatures and modest-to-heavy access.

Hotel & casinos with outside entrances use interesting air flows to separate 100°+F outdoor air from cool 71°F interior environment with few or no visible barriers. Large grocery stores use similar technology to separate ~74°F interior air from 34°F dairy shelves. Libraries and museums employ 'invisible curtains' to maintain optimum temperature and humidity for their collections without inhibiting human traffic.

The hotels and grocers initially used vertical transparent plastic sheets or ribbons for separation which introduced hygiene and aesthetic problems, alleviated by 'air curtains'.

Much effort is also made to inhibit micro-organisms with UV emitters, advanced air and water filters in air conditioning systems, and constant intense automated and human driven floor cleaners. Great emphasis was placed on improving interior and exterior air quality adjacent to large buildings following the discovery of Legionnaires disease.

Elevators and related people movers in rich hotels can likely be modified or designed to inhibit the spread of airborne micro-organisms using available technology; office buildings and condominiums more problematic. Small elevators primarily intended for disabled, children in strollers and elderly in libraries, theaters, gyms and smaller public buildings would probably require legislation with minimum safety guidelines.

Even so, I will wear a mask while out and about. 😎
 
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  • #22
russ_watters
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Imagine a warm, gentle 10-12 mph uniform breeze of clean filtered air coming down from the top.
Gentle? An ISO-5/Grade A clearnoom (cleaner than most pharma manufacturing facilities) or the inside of a laminar flow/downflow booth has a velocity of 90 fpm or 1 mph. That's with the entire ceiling covered with HEPA filters and the room velocity matching the filter velocity. Increasing the velocity beyond that would be problematic as the filter media area would need to be increased beyond what is typical for a HEPA filter (by a factor of 10!). The already folded into a dense pack, spaced maybe 1/16", and the package is generally a foot thick.

An elevator cab doesn't have room to fit such a system on the roof and wrapped around the sides. Just the ductwork alone would have to be about 1/4 the cross sectional area of the cab.

This system would also require a very large fan and produce a lot of heat, adding a cooling requirement.

This idea is a total non-starter (second time I've used that phrase in two posts...).
 
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  • #23
Vanadium 50
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Imagine a warm, gentle 10-12 mph uniform breeze of clean filtered air coming down from the top.
And becoming contaminated with virus and then going where, exactly?

I agree with Russ; this looks like a non-starter.
 
  • #24
bob012345
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Gentle? An ISO-5/Grade A clearnoom (cleaner than most pharma manufacturing facilities) or the inside of a laminar flow/downflow booth has a velocity of 90 fpm or 1 mph. That's with the entire ceiling covered with HEPA filters and the room velocity matching the filter velocity. Increasing the velocity beyond that would be problematic as the filter media area would need to be increased beyond what is typical for a HEPA filter (by a factor of 10!). The already folded into a dense pack, spaced maybe 1/16", and the package is generally a foot thick.

An elevator cab doesn't have room to fit such a system on the roof and wrapped around the sides. Just the ductwork alone would have to be about 1/4 the cross sectional area of the cab.

This system would also require a very large fan and produce a lot of heat, adding a cooling requirement.

This idea is a total non-starter (second time I've used that phrase in two posts...).
I think you are making the concept a lot harder than it needs to be. The input air may not need to be HEPA filtered cleanroom quality air, just air from a source away from people. Even recycling the cab air may not need such high technology. UV light may suffice. But you may be right and it may be a "non-starter". It was just an idea and a lot of ideas will need to be explored and they will.

So let me turn the question around and ask what would you and others suggest if the problem were posed to you "How do we make the elevator experience safer in the age of Covid-19?" As physics folks, what would you propose?
 
  • #25
anorlunda
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I think we exhausted the elevator/air curtain sub-topic. Let's re-focus on COVID.
 
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