A/C for Room Virus Removal

[Airbrush]

Here is the idea.  If an air conditioner was powerful enough, with intake and exhaust designed properly, you can remove Coronavirus (or any virus) from the air by the A/C moving the air faster than normal in an upward direction.  You want the air to circulate so fast that if someone sneezes the water droplets will remain inside the room only a few seconds before it is sucked out the ceiling vent. 

For cooling the room, the idea is cool air enters the room near the floor and the warmer air exits through a ceiling vent, the "return."   For heating the room you would also introduce warm air through low floor-vents, then the exhaust exits through the return in the ceiling.  The exhaust air is either expelled to the exterior, or recirculated through an ANTI-VIRUS filter with maybe UV light to kill ANY virus before the air enters the room through the floor intake.

The next pandemic could be an even nastier virus than Coronavirus.

Edited April 27, 2020 by Airbrush

[John Cuthber]

You can do it, but it's not easy.
https://en.wikipedia.org/wiki/Cleanroom

The problem is the hurricane you need

. A cough can travel as fast as 50 mph and expel almost 3,000 droplets in just one go. Sneezes win though—they can travel up to 100 mph and

https://www.lung.org/blog/sneeze-versus-cough

[J.C.MacSwell]

I've wondered if part of the problem in elderly care facilities is that the most vulnerable are more likely sitting or prone during interactions with others who are most often standing.

(like the 6 foot rule should be 8 feet for these interactions whenever possible, or somehow have the more vulnerable "upwind")

Having said that, shouldn't it work with gravity and draw the air downward? Taking it upward will suspend the larger droplets longer.

[MigL]

Droplets tend to fall out of suspension very quickly if the airflow is passed through a 'knock-out pot' ( engineering speak ).
In Physics terms, airflow is directed into a large chamber, where it is quickly decelerated, and then accelerated again.
The liquid droplets have much more inertia than air molecules, and cannot 'keep-up'; they drop out of suspension.

[Airbrush]

15 hours ago, J.C.MacSwell said:

I've wondered if part of the problem in elderly care facilities is that the most vulnerable are more likely sitting or prone during interactions with others who are most often standing.

(like the 6 foot rule should be 8 feet for these interactions whenever possible, or somehow have the more vulnerable "upwind")

Having said that, shouldn't it work with gravity and draw the air downward? Taking it upward will suspend the larger droplets longer.

Nursing homes have been a mass incubator for Covid-19 among the elderly.  Maybe attention should be given to ventilation.  Perhaps it would be better to have exhaust vents near the floor and fresh air is introduced into the room through the ceiling?   Clearly ventilation systems are suspect.  Just increasing the air flow would replace the virus air with cleaned air in about a minute.   Theaters, restaurants, and offices can boast of having an accelerated air replacement system to reduce chance for virus to hang around too long.

2 hours ago, MigL said:

Droplets tend to fall out of suspension very quickly if the airflow is passed through a 'knock-out pot' ( engineering speak ).
In Physics terms, airflow is directed into a large chamber, where it is quickly decelerated, and then accelerated again.
The liquid droplets have much more inertia than air molecules, and cannot 'keep-up'; they drop out of suspension.

Then in your opinion it would be more efficient to exhaust bad air through vents near the floor and introduce UV treated/filtered air into the room from the ceiling?

Edited April 28, 2020 by Airbrush

[J.C.MacSwell]

3 hours ago, MigL said:

Droplets tend to fall out of suspension very quickly if the airflow is passed through a 'knock-out pot' ( engineering speak ).
In Physics terms, airflow is directed into a large chamber, where it is quickly decelerated, and then accelerated again.
The liquid droplets have much more inertia than air molecules, and cannot 'keep-up'; they drop out of suspension.

Not familiar with the term, but similar in effect to a cyclonic filter?

I'm actually working right now on some swirl separators (for liquids but work similarly to some extent)

[swansont]

1 hour ago, Airbrush said:

Clearly ventilation systems are suspect. 

Clearly? What evidence is there to support this?

What information do you have on air filtration removal of the virus?

22 hours ago, Airbrush said:

The exhaust air is either expelled to the exterior, or recirculated through an ANTI-VIRUS filter with maybe UV light to kill ANY virus before the air enters the room through the floor intake.

Can you reconcile your need for a high flow rate with this filtration/exposure plan?

[J.C.MacSwell]

2 minutes ago, swansont said:

Clearly? What evidence is there to support this?

They've been suspect since the earliest cruise ship epidemics. Do you have reason to believe they don't affect the spread of Covid 19?

[swansont]

5 minutes ago, J.C.MacSwell said:

They've been suspect since the earliest cruise ship epidemics. Do you have reason to believe they don't affect the spread of Covid 19?

Not my burden of proof. But the scenario offered - nursing homes - has caretakers in close contact with multiple people on a daily basis. Has that been eliminated from being the prime suspect? 

[MigL]

34 minutes ago, J.C.MacSwell said:

Not familiar with the term, but similar in effect to a cyclonic filter?

I would think so.
Spinning separators work on density, to separate cream from milk, for example.
Knock-out pots ( or cyclonic filters ) work on the same principle as a snow fence.
Air has to accelerate to go over it, and the heavier snow drops out on the windward side.

For this same reason I wouldn't think ventilation systems would spread virus droplets.
Going through a high speed fan will get rid of most virus droplets.
( usually the knock-out pot or cyclonic separator is just ahead of the fan to collect dust, liquid or whatever you're separating out of the airstream )

Edited April 28, 2020 by MigL

[J.C.MacSwell]

15 minutes ago, swansont said:

Not my burden of proof. But the scenario offered - nursing homes - has caretakers in close contact with multiple people on a daily basis. 

The intent seems to be in devising a ventilation system that will help mitigate this, at least in part. A less than optimal ventilation system can facilitate spread, even if it doesn't introduce any virus on the supply side, simply by the airflow patterns it helps produce in the room. (though I'm fairly certain air from rooms designed for infected patients in hospitals is not returned unfiltered...which would lead me to think it is a concern)

46 minutes ago, swansont said:

 Has that been eliminated from being the prime suspect? 

Does it need to be?

47 minutes ago, MigL said:

I would think so.
Spinning separators work on density, to separate cream from milk, for example.
Knock-out pots ( or cyclonic filters ) work on the same principle as a snow fence.
Air has to accelerate to go over it, and the heavier snow drops out on the windward side.

For this same reason I wouldn't think ventilation systems would spread virus droplets.
Going through a high speed fan will get rid of most virus droplets.
( usually the knock-out pot or cyclonic separator is just ahead of the fan to collect dust, liquid or whatever you're separating out of the airstream )

I think there is still a concern with aerosols, and while the distinction is never cut and dried, they tend to stay suspended more than droplets.

[swansont]

Found this

https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article#tnF1

Strong airflow is alleged to be the culprit, since droplets travel further. Filtration doesn’t fix that. 

Quote

strong airflow from the air conditioner could have propagated droplets from table C to table A, then to table B, and then back to table C

 

23 minutes ago, J.C.MacSwell said:

Does it need to be?

Some basis for the discussion, other than conjecture, is needed.

[CharonY]

In biosafety facilities the workspace usually has a laminar air flow (top down) to minimize circulation of droplets or aerosols. Horizontal flows would in most cases result in broader distribution. I would think that a similar circulation (i.e. top down) could theoretically reduce spread, but are probably difficult to employ at scale.

[MigL]

Laminar flow simply means without ( or minimal ) turbulence.
Top-down flow is a method to minimize turbulence and horizontal flows ( which may spread contaminants )

[CharonY]

2 minutes ago, MigL said:

Laminar flow simply means without ( or minimal ) turbulence.
Top-down flow is a method to minimize turbulence and horizontal flows ( which may spread contaminants )

Yes, though for larger areas, maintaining true laminar flow can be difficult in terms of inlet-outlet configuration for the ducts to avoid turbulence.

Other systems, such as clean benches do the opposite, they maintain horizontal (mostly) laminar flow, in order to move particles away from items to be protected, but that would be exactly what we would want to avoid here. 

[StringJunky]

33 minutes ago, CharonY said:

In biosafety facilities the workspace usually has a laminar air flow (top down) to minimize circulation of droplets or aerosols. Horizontal flows would in most cases result in broader distribution. I would think that a similar circulation (i.e. top down) could theoretically reduce spread, but are probably difficult to employ at scale.

Is it done under negative or positive pressure? I think operating theatres are positive.

[CharonY]

It is independent of that, but most biosafety areas are under net negative pressure, as it is more important to make ensure that biohazards are less likely to escape. Conversely, a clean room (or operating theatre could run under positive pressure in order to keep contaminants out.

[StringJunky]

21 minutes ago, CharonY said:

It is independent of that, but most biosafety areas are under net negative pressure, as it is more important to make ensure that biohazards are less likely to escape. Conversely, a clean room (or operating theatre could run under positive pressure in order to keep contaminants out.

Thanks.

[MigL]

I'm only familiar with semiconductor clean rooms, which are not sterile as they are only concerned with particulate contaminants.
 

[iNow]

18 minutes ago, MigL said:

I'm only familiar with semiconductor clean rooms, which are not sterile as they are only concerned with particulate contaminants.

I was always a fan of the sticky mats we had to walk across before going in. Made me feel like I was on human flypaper. 

[John Cuthber]

13 hours ago, swansont said:

Filtration doesn’t fix that. 

The HEPA filters used in biohazard labs would fix it.

The problem is largely the noise from the fans.

6 hours ago, MigL said:

I'm only familiar with semiconductor clean rooms, which are not sterile as they are only concerned with particulate contaminants.

Bacteria and viruses are particulate.

The ones where they don't allow people are probably pretty near sterile for exactly that reason.

[swansont]

1 hour ago, John Cuthber said:

The HEPA filters used in biohazard labs would fix it.

The problem is largely the noise from the fans.

Not the problem described in the paper, which derives from in-room circulation. The air flow from the ventilation system assisted in getting the droplets to travel from table to table, before they would have had a chance to be filtered.

 

 

8 hours ago, iNow said:

I was always a fan of the sticky mats we had to walk across before going in. Made me feel like I was on human flypaper. 

We had a high-level person who insisted on stepping over the mats whenever he entered our lab. Grrr. (A tad like Pence not wearing a mask at the Mayo clinic)

Anyway, I took to calling it admiral-paper.  (And our visitors were referred to as sneetches, from the Dr. Seuss story)

[J.C.MacSwell]

47 minutes ago, swansont said:

We had a high-level person who insisted on stepping over the mats whenever he entered our lab. Grrr. (A tad like Pence not wearing a mask at the Mayo clinic)

Anyway, I took to calling it admiral-paper.  (And our visitors were referred to as sneetches, from the Dr. Seuss story)

Pence must figure he has a star on his belly...

[John Cuthber]

2 hours ago, swansont said:

We had a high-level person who insisted on stepping over the mats whenever he entered our lab.

I would put a lot more effort than I should into making the mat slightly bigger each time...

[Airbrush]

However you introduce air into a room (or workspace or sports arena), and how it exhausts, it would be safer for everyone that the air is circulated fast enough to minimize virus hanging around.  Faster air motion means more powerful A/C.  If the bad air exits the room through floor vents it could be piped to the roof and expelled to the environment which will deactivate the virus through wind dilution and UV light from the sun.  The fresh air intakes do NOT need to be treated or filtered for virus.  Just DON'T RECIRCULATE the same air.

Edited April 29, 2020 by Airbrush