New York, HVAC, COVID and Malls

[ew101]

The topic of possible COVID-19 transmission via or facilitated via HVAC is back in the news.  

 

https://www.cnbc.com/2020/06/29/malls-in-new-york-state-will-require-air-conditioning-systems-that-filter-the-coronavirus-gov-cuomo-says.html

 

ChengKp has briefed us on this, and the summary was- stateroom to stateroom transmission is a no, but public areas are well filtered but perhaps not to full hospital standards.  The HVAC industry has a white paper here, which says basically- yes aerosol transmission is potentially possible, and can be mitigated three ways: 1. Outside air 2:.Increased filtration (i.e. HEPA) 3. UV treatment.

 

https://www.ashrae.org/file library/about/position documents/pd_infectiousaerosols_2020.pdf

 

This topic might come up in the CDC/CLIA type discussions.   In my opinion, public areas on cruise ships would need HVAC changes - not cheap or easy- to being in more outside air and to recirculate as little as possible.  This is costly in terms of air conditioning/energy costs- there may be creative partial work arounds like heat exchangers.  (A side impact would be less indoor smoke).  I wonder if the UV treatment works?    Or can you filter more?  

 

Probably time (again) for the Bat-Signal.  

 

In a related topic, the dreaded and hated simple cloth masks did pretty well in a real world test here- I know a little statistics and n=140 is a reasonably good sample size.   

https://www.livescience.com/hair-stylists-infected-covid19-face-masks.html

 

http://www.tools4dev.org/resources/how-to-choose-a-sample-size/

 

[HaveWeMetYet]

41 minutes ago, ew101 said:

The topic of possible COVID-19 transmission via or facilitated via HVAC is back in the news.  

 

https://www.cnbc.com/2020/06/29/malls-in-new-york-state-will-require-air-conditioning-systems-that-filter-the-coronavirus-gov-cuomo-says.html

 

ChengKp has briefed us on this, and the summary was- stateroom to stateroom transmission is a no, but public areas are well filtered but perhaps not to full hospital standards.  The HVAC industry has a white paper here, which says basically- yes aerosol transmission is potentially possible, and can be mitigated three ways: 1. Outside air 2:.Increased filtration (i.e. HEPA) 3. UV treatment.

 

https://www.ashrae.org/file library/about/position documents/pd_infectiousaerosols_2020.pdf

 

This topic might come up in the CDC/CLIA type discussions.   In my opinion, public areas on cruise ships would need HVAC changes - not cheap or easy- to being in more outside air and to recirculate as little as possible.  This is costly in terms of air conditioning/energy costs- there may be creative partial work arounds like heat exchangers.  (A side impact would be less indoor smoke).  I wonder if the UV treatment works?    Or can you filter more?  

 

Probably time (again) for the Bat-Signal.  

 

In a related topic, the dreaded and hated simple cloth masks did pretty well in a real world test here- I know a little statistics and n=140 is a reasonably good sample size.   

https://www.livescience.com/hair-stylists-infected-covid19-face-masks.html

 

http://www.tools4dev.org/resources/how-to-choose-a-sample-size/

 

Whats missing in the hair salon article is whether or not the stylist had symptoms of covid or not. The verdict is still out if people without symptoms can spread but it is looking like the odds are very low.

[chengkp75]

First off, I will say that the vast majority of the ASHRAE paper concerned itself with aerosol transmission caused by airflow within the "breathing zone", or the airspace in a room.  There is no debate that the airflow from HVAC vents, return vents, and open windows or other natural ventilation can affect how an airborne virus can get transmitted further than the "sneeze/cough radius" of 6 feet.  And, there is no debate that installing better filters will produce cleaner air.  However, I have yet to see a paper that studies the amount of viable virus load there is at the filter inlet of a central HVAC system, to determine if there is a need for improved filtration in the first place.  Is/can the virus travel from the room to the filter and still be alive?  I don't know, but the CDC doesn't feel that duct cleaning is required, nor additional filtering, even on a ship where actual cases have been found, as part of remediation measures.  If the distances involved in the recirculation of air in the HVAC system is such that even with a room filled with covid infected people that there are very few to none viable viruses at the filter inlet, then saying that a HEPA filter is working to remove the virus is facetious, since there was nothing to remove in the first place.

 

While I think Gov. Cuomo has done a very good job in handling the pandemic in NY, I don't agree with his decision that malls, and malls only need improved filtration on their HVAC systems.  Personally, I feel that again, the distance involved with a centralized HVAC system in a mall is so much greater than a typical retail store or restaurant, that those businesses pose a more significant risk of transmission via HVAC than a mall.  Also, the airflow in a mall is so much more dispersed than a restaurant or shop (who hasn't felt a cold draft in a restaurant at times?).

[ew101]

Thanks, ChengKP for jumping in on this.  We have excellent data on person to person direct droplet transmission.  And the idea a draft might waft the droplets around seems obvious.   But are ultra fine droplets a long way away a viable transmission method?   The fact you can smell secondhand smoke in a ship lobby says yes air is being recirculated, and yes fine particles are in play.  Can the smallest droplets carrying virus particles survive a fifty foot trip though intakes, ducts, filters and outlets?   If this was true we would all be at risk buying groceries - and we are not.  Bigger indoor areas like malls seem safer indeed.  

 

There was that famous case of the church choir- but they were singing and reasonably close together.  

 

I think the goal needs to be- what can be done to make the inside of a ship the safest it can be.  And it's not more hand sanitizer.  

 

Edited June 29, 2020 by ew101

[chengkp75]

There was also the Chinese restaurant, where the infected person was directly under the AC outlet, and the airflow sent the virus further than the "sneeze radius".

 

From a quick search, coronavirus is about 0.125 micron in size, while the smallest smoke particles (those that travel the furthest) are in the 0.002 - 0.020 micron size, so I feel that the larger, and presumably heavier virus particles would not travel as far.

 

As long as the most prevalent and potent means of transmission is coughing/sneezing/breathing on each other, there are other means of remediation that will work to slow transmission better than HEPA filters.

[KirkNC]

The evolution of knowledge on the virus goes on. AC and surface spread are not longer big items while exhaled breath is.

[ontheweb]

2 hours ago, KirkNC said:

The evolution of knowledge on the virus goes on. AC and surface spread are not longer big items while exhaled breath is.

And yet all businesses including cruise lines talk about all the extra cleaning and disinfecting they will do before opening. Not that that in itself is a bad thing, but as far as this virus goes it is like many airline security measures more for show than anything else.

[chengkp75]

49 minutes ago, ontheweb said:

And yet all businesses including cruise lines talk about all the extra cleaning and disinfecting they will do before opening. Not that that in itself is a bad thing, but as far as this virus goes it is like many airline security measures more for show than anything else.

Surface cleaning is still important, when in croweded situations.

[ontheweb]

1 hour ago, chengkp75 said:

Surface cleaning is still important, when in croweded situations.

I was not disputing that. I'm sure it was important before Covid 19 and will continue to be important after this virus is somehow (hopefully) conquered. I was just saying that in the present pandemic the extra cleaning is probably more for show and the appearance of doing something. This is especially true as transmission from surfaces has pretty much been discounted as a means of transmission.

[ew101]

If I ran a major cruise line what I would do right this minute is find the best cruise ship engineer I knew 🙂 and roll out a set of ship blueprints and say this:

 

If this was 1917, the only ventilation you had was pulling in outside air.  We have this now in cabins, plus AC.  Can we do this for public areas?  Change the model to have positive pressure and maximum outside air and the bare minimum of recirculation.  So air comes in from the outside vents, is chilled and pumped into the public spaces from above then is vented out right away.  This will involve cutting lots of new vents (lower outside walls and in floors).  And is not how it has been done.  But can it be done?  The idea is to push the droplets down then out.   If it works for guest cabins, can it be scaled up to larger public spaces?  There is of course energy wastage - but there may be creative ways around that.  

Edited June 30, 2020 by ew101

[chengkp75]

41 minutes ago, ew101 said:

If I ran a major cruise line what I would do right this minute is find the best cruise ship engineer I knew 🙂 and roll out a set of ship blueprints and say this:

 

If this was 1917, the only ventilation you had was pulling in outside air.  We have this now in cabins, plus AC.  Can we do this for public areas?  Change the model to have positive pressure and maximum outside air and the bare minimum of recirculation.  So air comes in from the outside vents, is chilled and pumped into the public spaces from above then is vented out right away.  This will involve cutting lots of new vents (lower outside walls and in floors).  And is not how it has been done.  But can it be done?  The idea is to push the droplets down then out.   If it works for guest cabins, can it be scaled up to larger public spaces?  There is of course energy wastage - but there may be creative ways around that.  

Well, if you have positive pressure in the public areas, and positive pressure in the cabins, then any time you open a cabin door, air will rush in from the much larger public space ventilation, negating your positive pressure in the cabins for viral isolation as well as smoke containment.  As for exhaust vents at a lower level, this is antithesis to AC, but is common for forced hot air central heating systems.  If you take the air from low down, it is not the warmest (i.e. the "oldest" air in the space), since the warm air rises, so you would have air stagnating in the space.

 

As for energy wastage, the typical mixture is 20% fresh air and 80% recirculated air, so moving to a strictly once through system with no recirculation, energy will ramp up about 3-4 times for air conditioning, which is why buildings and ships use the recirculation model.  Again, why should cruise ships be singled out for costly modifications, when nearly every building on earth that has a central HVAC system uses the exact same system.

 

What you are looking for would be a system that distributes the cooled air, whether outside or recirculated, in a method where the air velocity is much lower, and the air distributes across the ceiling to then flow down by convection to the lower part of the room, and then allow convection to bring the warm air up to vents around the perimeter.

 

Positive or negative pressure in a space has nothing to do with spread of a virus, it is only important when you have one space that is possibly infected, and one space that is closed off from that, and you wish to keep that second space ensured of non-infection, so you have positive pressure in the second space, and negative pressure in the first space, so when a door is opened, air flows into the first (possibly infected) space always.

[ew101]

Ok now we are making progress.  Experts have been consulted.  So I'm in my stateroom having tea and reading a book- I'm 100% safe.  Out for a socially distant walk on the promenade (not on most lines lol) or six feet apart on a lounger- still safe.  If I am at dinner, and the couple four feet way at the next table are shedding virus via droplets,  those are wafting by.  If I'm at the bar- I'm breathing recently shared air and possibly droplets.  

 

Can the public area airflow be re-directed so what happens at the next table stays at the next table?  Either up to down or down to up.  Or at a table by the window or wall just out.   We have this in cold climates with "air doors"- yes it is unfair but we are fighting the "Floating Petri Dish" model with engineering.   As I write this they are in certain places re-closing bars and health clubs - both are major amenities on cruise ships. 

 

Genting Cruise Line just said they had 100% fresh air in staterooms- so not an academic discussion at all. https://www.foxnews.com/travel/dream-cruises-first-cruise-line-world-operations-coronavirus 

Edited June 30, 2020 by ew101

[npcl]

On 6/29/2020 at 11:21 AM, chengkp75 said:

First off, I will say that the vast majority of the ASHRAE paper concerned itself with aerosol transmission caused by airflow within the "breathing zone", or the airspace in a room.  There is no debate that the airflow from HVAC vents, return vents, and open windows or other natural ventilation can affect how an airborne virus can get transmitted further than the "sneeze/cough radius" of 6 feet.  And, there is no debate that installing better filters will produce cleaner air.  However, I have yet to see a paper that studies the amount of viable virus load there is at the filter inlet of a central HVAC system, to determine if there is a need for improved filtration in the first place.  Is/can the virus travel from the room to the filter and still be alive?  I don't know, but the CDC doesn't feel that duct cleaning is required, nor additional filtering, even on a ship where actual cases have been found, as part of remediation measures.  If the distances involved in the recirculation of air in the HVAC system is such that even with a room filled with covid infected people that there are very few to none viable viruses at the filter inlet, then saying that a HEPA filter is working to remove the virus is facetious, since there was nothing to remove in the first place.

 

While I think Gov. Cuomo has done a very good job in handling the pandemic in NY, I don't agree with his decision that malls, and malls only need improved filtration on their HVAC systems.  Personally, I feel that again, the distance involved with a centralized HVAC system in a mall is so much greater than a typical retail store or restaurant, that those businesses pose a more significant risk of transmission via HVAC than a mall.  Also, the airflow in a mall is so much more dispersed than a restaurant or shop (who hasn't felt a cold draft in a restaurant at times?).

There are a couple of situations where you are likely to get aerosol instead of droplet behavior.  One is in the hospital when a patient is being intubated (or potentially in the medical center). Another is when using positive pressure masks, such a cpap machines.  As one paper puts it

 

In the U.S., emergency plans developed by states for a shortage of ventilators include using positive airway pressure machines — like those used to treat sleep apnea — to help hospitalized people with less severe breathing issues.

While that measure could stretch the supply of ventilators and save lives, it has a major drawback. Officials and scientists have known for years that when used with a face mask such alternative devices can possibly increase the spread of infectious disease by aerosolizing the virus, whether used in the hospital or at home.

 

As long as cabin air is not recycled, not much of an issue on ships, though there might be virus exposure into the adjoining hallways and the crew servicing the room of a passenger that uses cpap might be more at risk.

Edited June 30, 2020 by npcl

[ew101]

https://news.harvard.edu/gazette/story/2020/06/air-conditioning-may-be-factor-in-covid-19-spread-in-the-south/ 

 

This has no real facts but I wonder if the recirculation percentage can be reduced on a ship in common areas easily?  

[chipmaster]

On 6/29/2020 at 10:12 AM, ew101 said:

The topic of possible COVID-19 transmission via or facilitated via HVAC is back in the news.  

 

https://www.cnbc.com/2020/06/29/malls-in-new-york-state-will-require-air-conditioning-systems-that-filter-the-coronavirus-gov-cuomo-says.html

 

ChengKp has briefed us on this, and the summary was- stateroom to stateroom transmission is a no, but public areas are well filtered but perhaps not to full hospital standards.  The HVAC industry has a white paper here, which says basically- yes aerosol transmission is potentially possible, and can be mitigated three ways: 1. Outside air 2:.Increased filtration (i.e. HEPA) 3. UV treatment.

 

https://www.ashrae.org/file library/about/position documents/pd_infectiousaerosols_2020.pdf

 

This topic might come up in the CDC/CLIA type discussions.   In my opinion, public areas on cruise ships would need HVAC changes - not cheap or easy- to being in more outside air and to recirculate as little as possible.  This is costly in terms of air conditioning/energy costs- there may be creative partial work arounds like heat exchangers.  (A side impact would be less indoor smoke).  I wonder if the UV treatment works?    Or can you filter more?  

 

Probably time (again) for the Bat-Signal.  

 

In a related topic, the dreaded and hated simple cloth masks did pretty well in a real world test here- I know a little statistics and n=140 is a reasonably good sample size.   

https://www.livescience.com/hair-stylists-infected-covid19-face-masks.html

 

http://www.tools4dev.org/resources/how-to-choose-a-sample-size/

 

 

If people would just wear masks we'd not be here in this mess

[Sue from Canada]

2 hours ago, chipmaster said:

 

If people would just wear masks we'd not be here in this mess

And wash your hands, isolate and stay six feet apart from anyone who steps "into your circle."  

[chengkp75]

12 hours ago, ew101 said:

Ok now we are making progress.  Experts have been consulted.  So I'm in my stateroom having tea and reading a book- I'm 100% safe.  Out for a socially distant walk on the promenade (not on most lines lol) or six feet apart on a lounger- still safe.  If I am at dinner, and the couple four feet way at the next table are shedding virus via droplets,  those are wafting by.  If I'm at the bar- I'm breathing recently shared air and possibly droplets.  

 

Can the public area airflow be re-directed so what happens at the next table stays at the next table?  Either up to down or down to up.  Or at a table by the window or wall just out.   We have this in cold climates with "air doors"- yes it is unfair but we are fighting the "Floating Petri Dish" model with engineering.   As I write this they are in certain places re-closing bars and health clubs - both are major amenities on cruise ships. 

 

Genting Cruise Line just said they had 100% fresh air in staterooms- so not an academic discussion at all. https://www.foxnews.com/travel/dream-cruises-first-cruise-line-world-operations-coronavirus 

I will cautiously call BS on Genting's claim to moving to 100% fresh air in staterooms, as this is a 21 year old ship supposedly outfitted to meet covid requirements without a major refit.  I suspect that they are playing on the fact that the ship's HVAC design already takes all of its air in from outside, it doesn't say that they are exchanging that air 100% (straight through system).

 

I'm sure there could be airflow studies to determine how best to control air flow, but it would require that each individual space be studied in either true wind tunnels or on computer simulations to see what combination of registers, size and shape of registers, and baffling would be needed for optimum airflow.  And then trying to reroute ductwork around existing electrical cables and plumbing in the ceilings of ship's spaces.  Not a quick and easy fix.

 

Bars are closing because you are in close proximity, and you have to remove your mask to drink.  Health clubs are closing because exercising with a mask is very difficult due to the restriction in airflow, and the heavy breathing accompanying exercise will spread droplets further.

8 hours ago, ew101 said:

https://news.harvard.edu/gazette/story/2020/06/air-conditioning-may-be-factor-in-covid-19-spread-in-the-south/ 

 

This has no real facts but I wonder if the recirculation percentage can be reduced on a ship in common areas easily?  

Not easily, but it could be done, again at the expense of additional power.  And, many land establishments that use AC don't really have an air exchange system like ships do that constantly add fresh air and remove exhaust air.  Look at a place (restaurant or home) that uses a window AC unit.  All the windows and doors are closed, and even when the "outside vent" is open on the AC unit, it can only bring in as much fresh air as can be exhausted somewhere else, or you pressurize the room.  Where is the exhaust?  Most frame construction is not air tight, so you are relying on whenever a door opens, or pushing air through the cracks in the building for your air exhaust.  Not a real quantifiable amount of air exchange.

[ew101]

Ok more progress.  Thank you.  So if we take a lovely ship like the Rotterdam, and pick out a public space.  Do a simulation of adding a bunch of floor and wall vents.  The idea is as guests sneeze and cough and even talk the droplets go largely down and out or out a wall vent but not sideways.   So you establish a new airflow pattern.  This is super hard if you have take apart stateroom ceilings apart and reroute stuff but should be possible.  The idea is safe(er) indoor public spaces can be created.    The same with cabin corridors.  You might need new intakes every six feet so any droplets go sideways and out and not 25 feet forward or aft.     

 

It is the airflow in the sneeze/droplet zone as you have pointed out that is critical.  I keep thinking outdoors is safer but there have been a few beach/event outbreaks.   

 

Genting may be fine for a while with no material changes to the ship as people from Taiwan are rule followers- and will wear masks.  But not at the bar or while actually eating.   One new outbreak aboard and the port/health authorities (already gun-shy) will go berserk.  

[chipmaster]

15 hours ago, Sue from Canada said:

And wash your hands, isolate and stay six feet apart from anyone who steps "into your circle."  

 

Believe it or not in the Far East you don't have a 2M / 6 feet circle and they have managed amazingly well 

[wander]

Regarding the "Far East" (and I might add many Asian countries) - yes probably less personal space is available BUT MASKS are very  common in public places - on the streets or simply outdoors, for several reasons years and years before the COVID-19 invasion.    So, wearing a mask does not have the same implications for many compared to our folks.  Also, in at least some "Far East" countries if the leaders say "You shall wear a mask when in public" - folks do.  It is treated as an order with teeth, NOT as a  suggestion.

[chipmaster]

2 hours ago, wander said:

Regarding the "Far East" (and I might add many Asian countries) - yes probably less personal space is available BUT MASKS are very  common in public places - on the streets or simply outdoors, for several reasons years and years before the COVID-19 invasion.    So, wearing a mask does not have the same implications for many compared to our folks.  Also, in at least some "Far East" countries if the leaders say "You shall wear a mask when in public" - folks do.  It is treated as an order with teeth, NOT as a  suggestion.

 

Sad in the West the leaders can't set an example and make it about national emergency and a law.  People in the US have twisted this into some constitutional right to be stupid in a emergency.  It is the strange nature of the Americans and their freedom, freedom to be stupid I guess.       It was once a place where people would unit when faced with calamity or crisis, but now calamity and crisis seems to be an opportunity to be different and not give a little.   Most arguments have been belittling or negative, a society can't exist with billions without rules and norms that people are willing to follow.  In times of emergency people must make sacrifices but Americans strangely don't feel they need to sacrifice or give a anything,well at least enough of them to make lots of trouble. 

[lucymorgan]

This is a very interesting discussion.    

 

I know it doesn't protect my home from the virus, but when the Australian bushfires were raging, our city was covered in smoke and air purifiers sold out across the country.  I ordered this one https://www.breville.com/au/en/products/air-purifier/bap500.html  in January but it didn't arrive until April.  They asked me if I still wanted it as the bushfires were out.   I said yes because we have a slow combustion wood heater and because it might have a small effect on cleaning the air in our living room of any virus particles.  I have been very impressed by what it does.  If I open the fireplace to put more wood in, it immediately senses this from about 3 metres away and zooms up until the air is clean again.  If I cook something in my kitchen (about 5 metres away), it does the same - all automatic.    So although its effect on virus particles is debatable and it was expensive, I am pretty glad I went ahead with the purchase.  🙂 

 

Maybe I could cruise with a mini version 🤣 - just joking

Edited July 2, 2020 by lucymorgan

[UnorigionalName]

On 6/29/2020 at 4:52 PM, ew101 said:

Thanks, ChengKP for jumping in on this.  We have excellent data on person to person direct droplet transmission.  And the idea a draft might waft the droplets around seems obvious.   But are ultra fine droplets a long way away a viable transmission method?   The fact you can smell secondhand smoke in a ship lobby says yes air is being recirculated, and yes fine particles are in play.  Can the smallest droplets carrying virus particles survive a fifty foot trip though intakes, ducts, filters and outlets?   If this was true we would all be at risk buying groceries - and we are not.  Bigger indoor areas like malls seem safer indeed.  

 

There was that famous case of the church choir- but they were singing and reasonably close together.  

 

I think the goal needs to be- what can be done to make the inside of a ship the safest it can be.  And it's not more hand sanitizer.  

 

 

The thought is that smaller droplets travel further, but dry out easier.  And when they dry out the virus becomes less viable over time.  And big droplets protect the virus, but don't travel as far.  That's where all the stuff saying "6-feet" came from, this person in like the 70's thought that's as far as droplets can go.

 

It turns out it's not that simple, that there's not this dichotomy, and that live viruses can actually travel pretty far.  When you breath or sing or sneeze or cough, the small droplets travel together in this nice warm humid cloud and protect each other from drying out, so they remain viable for a good amount of time and can travel pretty far.

 

Also why it's thought now that outdoors is relatively low risk, because of more wind blowing apart and drying out these humid virus clouds, instead of nice still indoor air where it can waft around, and UV to rapidly kill the viral particles.

 

So that's why the thought of getting sucked into HVAC, and live particles coming out the other side seems unlikely.  The particles will dry out pretty quickly, no matter the size, and it seems currently unlikely for COVID to get transmitted this way, though there are other infectious agents that definitely can travel through HVAC.

 

Really though, this shouldn't be taken as a comforting fact for returning to cruising, because it means all these uncontrollable outbreaks on cruise ships is happening despite the fact that it's not from going in and out of the HVAC, it doesn't need to, it's pretty freaking infectious already.

[chengkp75]

7 hours ago, UnorigionalName said:

So that's why the thought of getting sucked into HVAC, and live particles coming out the other side seems unlikely.  The particles will dry out pretty quickly, no matter the size, and it seems currently unlikely for COVID to get transmitted this way, though there are other infectious agents that definitely can travel through HVAC.

Yes, this is why I'm not going down the rabbit hole of trying to design "safe" airflows for cruise ships, until they are mandated for every place of business in the US that has a central ventilation system.

[ontheweb]

2 hours ago, chengkp75 said:

Yes, this is why I'm not going down the rabbit hole of trying to design "safe" airflows for cruise ships, until they are mandated for every place of business in the US that has a central ventilation system.

The question remains however will the CDC require that "rabbit hole" be explored.