What about the ventilation system on our ships?

[Sherry H]

I have been trying to do some research regarding ventilation on cruise ships.  I found an article that compared airplanes to ships which I found very interesting.

 

The article stated the closeness of passengers, germs on surfaces, coughing, sneezing etc. is an issue on an airplane.  However, the air in the ventilation system is very clean.  It is a mixture of recirculated and fresh air which passes through a HEPA filter.  HEPA filters are used in hospitals and filter out viruses.

 

Not so with the ventilation system on cruise ships. The filters used on the ships DO NOT filter out viruses! The ventilation system is recirculating air with neighboring cabins. It is believed this is why, even after being quarantined to your cabin, you are exposed to viruses.   You are breathing contaminated air!

 

I am hoping someone with a knowledge of the ventilation systems on ships can tell us how it can be what can be done and how it might be improved.

 

 

[CruiserBruce]

If you do a search around the board, you will see many discussions of the topic. Usually the member of the boards (whom I can't "tag" right now), with specific knowledge and experience, comes along and clarifies the issue. Most of what you say is actually not true....for example, the air doesn't circulate between cabins.

 

Its my understanding that a HEPA filter can't catch a single virus "cell", but as viruses typically travel in clums, they can be caught in HEPA filters.

[bluesea321]

6 minutes ago, Sherry H said:

I have been trying to do some research regarding ventilation on cruise ships.  I found an article that compared airplanes to ships which I found very interesting.

 

The article stated the closeness of passengers, germs on surfaces, coughing, sneezing etc. is an issue on an airplane.  However, the air in the ventilation system is very clean.  It is a mixture of recirculated and fresh air which passes through a HEPA filter.  HEPA filters are used in hospitals and filter out viruses.

 

Not so with the ventilation system on cruise ships. The filters used on the ships DO NOT filter out viruses! The ventilation system is recirculating air with neighboring cabins. It is believed this is why, even after being quarantined to your cabin, you are exposed to viruses.   You are breathing contaminated air!

 

I am hoping someone with a knowledge of the ventilation systems on ships can tell us how it can be what can be done and how it might be improved.

 

 

 

I could address your questions but it would lead to countless arguments as this topic has in the past.  However there are some points I can likely make without much controversy.  The filters on the ship cabins are indeed not HEPA as you correctly state.  The cabins are kept under positive pressure (for fire safety) and therefore a small amount of cabin air is constantly leaking into the hallways and a larger amount of cabin air goes into the hallways when you open the door.  And lastly, the common areas, dining, theater, atrium, clubs, etc. all have recirculated air.  It would be very expensive (not feasible) to retrofit HVAC systems to not recirculate air.

[Sherry H]

Well...….…..OK...……...I had not seen this subject on the HAL board.  So, I did a "search" and found lots on the 

RC board.  Interesting "stuff"

[chengkp75]

1 hour ago, Sherry H said:

Well...….…..OK...……...I had not seen this subject on the HAL board.  So, I did a "search" and found lots on the 

RC board.  Interesting "stuff"

That professor who wrote the article I believe you are referencing, in a later interview clarified his remarks as "on a cruise ship, if you are in a public space, you are in a ventilation soup" or some similar reference, but the clarification of "public spaces" is very important.  First off, he does recognize that air is not recirculated between cabins.  Cabins receive fresh outside air, and cabins exhaust air to the outside.  Cabins do recirculate air, but only within that cabin, much as your window AC unit recirculates air within the room it is in.  Secondly, the distances involved in the recirculation of air in an aircraft and a cruise ship are orders of magnitude different, and the much longer distances air needs to travel to get from one place on a ship and back to that same place is so long that there is no evidence that viruses like covid can travel that far and still be viable.

[cbr663]

OP, you may find this article interesting as it does mention HVAC systems on cruise ships.  Right now there appears to be conflicting viewpoints on virus transmission through HVAC systems.

 

https://nationalpost.com/health/covid-19-likely-spread-by-building-ventilation-say-canadian-researchers-working-on-an-hvac-fix

[chengkp75]

26 minutes ago, cbr663 said:

OP, you may find this article interesting as it does mention HVAC systems on cruise ships.  Right now there appears to be conflicting viewpoints on virus transmission through HVAC systems.

 

https://nationalpost.com/health/covid-19-likely-spread-by-building-ventilation-say-canadian-researchers-working-on-an-hvac-fix

First off, the "chinese restaurant" case cited notes that the air flow from an AC outlet, caused the virus to spread further than coughing or sneezing would carry, so that is not a problem of the HVAC system, unless you are going to stop all ventilation completely.  As for legionnaires', that virus starts in the HVAC system, at the condensation formed at the cooling coils or cooling towers, it does not carry from one space, through the return ducts, past the coolers, and then through the supply ducts to another place.  Further, as I have noted before, the air in cruise ship cabins is not mixed with air from other cabins.  And, finally, cruise ship HVAC systems are required to have sanitizing pads in the condensate pans to prevent the formation and spread of bacteria like legionella.

[Stratheden]

How often are filters either changed or cleaned on a cruise ship?

[chengkp75]

9 minutes ago, Stratheden said:

How often are filters either changed or cleaned on a cruise ship?

Monthly is typical.

[Sherry H]

chengkp75, thank you so much for "weighing in".  I always read your explanations and have great respect for your knowledge.

 

[prescottbob]

1 hour ago, chengkp75 said:

Monthly is typical.

In so far as the individual ‘cabin intake and exhaust filters (s)’ you will need to request the filter(s) has to be changed monthly (if on longer cruises) if you have allergy / breathing issues, 

The good folks on board HAL will respond when notified but there is no monthly changing of filters (regular scheduled maitenace-wise) that I’ve ever noted.

Usually on past cruises (and the older HAL ships), the AC would be inefficient, my better half would complain about breathing at sleep issues or sometimes there would be several small visible chunks of carbon on the cabin  desk coming from  the outlet vent (sometimes I need to take a picture of the situation for the CS folks to prove my point).

So...me thinks HEPA filters or any sort of anti viral filtration would not be a non-concern at this point since such filtration is non-existent in / on any large gathering entities (e.g. hotels, convention venues, airlines, cruise ships, your local supermarkets, etc.)

 

Enough said.

Enjoy & be well.

Bob

[cbr663]

13 hours ago, chengkp75 said:

First off, the "chinese restaurant" case cited notes that the air flow from an AC outlet, caused the virus to spread further than coughing or sneezing would carry, so that is not a problem of the HVAC system, unless you are going to stop all ventilation completely.  As for legionnaires', that virus starts in the HVAC system, at the condensation formed at the cooling coils or cooling towers, it does not carry from one space, through the return ducts, past the coolers, and then through the supply ducts to another place.  Further, as I have noted before, the air in cruise ship cabins is not mixed with air from other cabins.  And, finally, cruise ship HVAC systems are required to have sanitizing pads in the condensate pans to prevent the formation and spread of bacteria like legionella.

 

As I stated in my post, conflicting view points.

[Heartgrove]

I recall there being issues when inconsiderate/unknowing passengers would block their door to their balcony open. That would in turn upset the ability of the system to keep the surrounding cabins in a temperate zone. Cabins must then be interconnected with trunks off of the zone system.

[chengkp75]

54 minutes ago, Heartgrove said:

I recall there being issues when inconsiderate/unknowing passengers would block their door to their balcony open. That would in turn upset the ability of the system to keep the surrounding cabins in a temperate zone. Cabins must then be interconnected with trunks off of the zone system.

Nope.  There are two AC systems.  One system takes fresh outside air, cools it, and delivers it to blocks of cabins (no mixing of air, straight from outside to cabin).  This system is balanced by the bathroom exhaust, which takes air from a bank of cabins, and delivers it outside (again, no mixing between cabins, straight from cabins to outside).  The other system recirculates air within a cabin, sending it over a separate cooler, controlled by the cabin thermostat.  

 

Now, the fresh air supply system delivers slightly more air to the cabin than the bathroom exhaust takes away, keeping the cabin under a slight positive pressure, with regards to outside and the passageway, in order to keep smoke from migrating into cabins during a fire.  When you prop open the balcony door, creating a large opening, the pressure in that cabin drops to outside pressure, and the fresh air delivery system all flows to that cabin (since every other cabin is at a higher pressure, the air flows in the path of least resistance, to the one place where the pressure is lowest, the cabin with the open balcony door).  This means that all the remaining cabins receive less cool fresh air, and they start to warm up.  That is the interrelationship between cabins, but again, there is no ducting that takes air from multiple cabins and recirculates it back to multiple cabins.

[Heartgrove]

3 minutes ago, chengkp75 said:

Nope.  There are two AC systems.  One system takes fresh outside air, cools it, and delivers it to blocks of cabins (no mixing of air, straight from outside to cabin).  This system is balanced by the bathroom exhaust, which takes air from a bank of cabins, and delivers it outside (again, no mixing between cabins, straight from cabins to outside).  The other system recirculates air within a cabin, sending it over a separate cooler, controlled by the cabin thermostat.  

 

 

Thank you for a more detailed explanation and that then makes sense. I have more experience with berthing space ventilation. :)

[chengkp75]

7 minutes ago, Heartgrove said:

 

Thank you for a more detailed explanation and that then makes sense. I have more experience with berthing space ventilation. 🙂

Or lack thereof.  😉

[cruiserchuck]

Unless you never leave your cabin, and somehow manage to get into the cabin without going through a common area, you are going to be breathing some unfiltered air that others are also breathing.  

 

Until there is a vaccine for the virus, I am going to be very reluctant to go on a cruise.  

Edited May 8, 2020 by cruiserchuck

[chengkp75]

12 minutes ago, cruiserchuck said:

Unless you never leave your cabin, and somehow manage to get into the cabin without going through a common area, you are going to be breathing some unfiltered air that others are also breathing.  

 

Until there is a vaccine for the virus, I am going to be very reluctant to go on a cruise.  

And, again, there is no data to support the transmission of virus through an AC system, or every building in the world would be shut down.

[ontheweb]

14 hours ago, chengkp75 said:

And, again, there is no data to support the transmission of virus through an AC system, or every building in the world would be shut down.

I don't know how often you can give facts and still not educate those who want to stick to their belief. But thank you for your patience and persistence in doing so.

[chengkp75]

21 minutes ago, ontheweb said:

I don't know how often you can give facts and still not educate those who want to stick to their belief. But thank you for your patience and persistence in doing so.

Thank you, Sancho, on to the next windmill!!

[ontheweb]

1 minute ago, chengkp75 said:

Thank you, Sancho, on to the next windmill!!

You're welcome. I for one am grateful for all I have learned from you. I'm sure there are many others in the same boat. Oops, unintended pun.

[Ansula]

On 5/9/2020 at 1:17 AM, chengkp75 said:

And, again, there is no data to support the transmission of virus through an AC system, or every building in the world would be shut down.

What about the recent corona outbreaks on large navy vessels ( an American and a French aircraft carrier)? Is there a more plausible explanation than the AC system?

[AlanF65]

38 minutes ago, Ansula said:

What about the recent corona outbreaks on large navy vessels ( an American and a French aircraft carrier)? Is there a more plausible explanation than the AC system?

Everyone eats together 3x a day, they are in cramped quarters 24x7, they may have different air systems than cruise ships  based on different criteria based on damage containment, fire and flood.

[chengkp75]

1 hour ago, Ansula said:

What about the recent corona outbreaks on large navy vessels ( an American and a French aircraft carrier)? Is there a more plausible explanation than the AC system?

Have you seen the berthing quarters on a Navy ship?

 

https://www.google.com/search?q=berthing+on+aircraft+carrier&tbm=isch&source=iu&ictx=1&fir=-dSQa5YSVEiq5M%3A%2CRirlWJpVySnxDM%2C_&vet=1&usg=AI4_-kQQdg-qOJCpU69GLYLjejV9JnEK3g&sa=X&ved=2ahUKEwig-NfStZbqAhWmm-AKHdOdC0kQ9QEwAnoECAMQIg#imgrc=-dSQa5YSVEiq5M:

 

Some of these guys sleep 3 high, and heads within a foot of each other when the bunks are "cornered" together.  And, actually, since the Navy does not need to make a profit, and they are more concerned about shipboard fire, they don't recirculate any air, it is all fresh air in and stale air out.

[Hlitner]

2 hours ago, Ansula said:

What about the recent corona outbreaks on large navy vessels ( an American and a French aircraft carrier)? Is there a more plausible explanation than the AC system?

My goodness, have you ever bee on a large navy vessel?   The crew lives on top of each other (literally) and social distancing is virtually impossible in the crew quarters, crew eating areas and many work areas.  It is hard to imagine a worse situation (for a virus) then a naval vessel.

 

Hank