Are cruise ships able to re-route HVAC/Air? Why they re-circulate air?

[ontheweb]

3 hours ago, chengkp75 said:

This is a prime example of a non-technical person writing about a technical matter.  I have always said that the air in public spaces has been recirculated, and this has been done for decades, I don't know what ship this guy is speaking about of once through AC, but I digress.  He also does not understand how a heat recovery wheel works.  Where is the heat "caught"?  Heat can only be "caught" by something cooler than what you are trying to capture heat from.  The air that is drawn out of an air conditioned space for recirculation is almost always cooler than the outside air, and warmer than the air being supplied as AC.  So, you can't transfer the heat from the recirculation air to the outside, and if you transfer it to the AC air, you are just heating the air you just cooled by the AC.  Nope.  Note that the description of the heat recovery wheel is not a quote from the technical expert quoted elsewhere in the article.  The heat recovery wheel takes the air that is being exhausted to the outside (typically 20% of air volume per minute), and which is cooler than the outside, and this air, which you don't care about, is heated by cooling the incoming fresh air (again 20% of air volume per minute), and since you now have cooler fresh air coming into the ship, you need less energy to cool that air to the proper temperature.

 

They do not specify what the "fan coil" units are set up for.  For public spaces, these are large fan coil units that cool the recirculation air, but for cabins, each cabin has it's own fan coil unit, where the fan takes the air from the cabin, passes it over the cooling coil, and returns the air to the cabin.  This is the AC that is controlled by the cabin thermostat.  There is another AC system supplying cool fresh air to the cabin, and that cannot be controlled by the cabin thermostat.

 

The only real change that this RCI article speaks about over what I have worked on aboard ships for the past 30 years, is the use of CO2 measuring to adjust the cooling load of a public space to the heat load of the number of people in the space.

You have incredible patience dealing with laymen who think they are an expert because they read something.

 

It reminds me of a sign that is in our veterinarian's office. "You're google search is not equal to my medical degree."

[bluesea321]

10 minutes ago, ontheweb said:

You have incredible patience dealing with laymen who think they are an expert because they read something.

It reminds me of a sign that is in our veterinarian's office. "You're google search is not equal to my medical degree."

 

And the above is an example of someone posting without knowing the facts.  This particular "layman" happens to be a Mechanical Engineer with a Ph.D. in Fluid and Heat Transfer and 40 years of experience on the subject so hardly a "layman" who reads something.   But I got a chuckle out of your vets' sign, good one.  🙂

[Toofarfromthesea]

2 hours ago, bluesea321 said:

 

And the above is an example of someone posting without knowing the facts.  This particular "layman" happens to be a Mechanical Engineer with a Ph.D. in Fluid and Heat Transfer and 40 years of experience on the subject so hardly a "layman" who reads something.   But I got a chuckle out of your vets' sign, good one.  🙂

 

And yet you expect a puff piece aimed at the general public to be technically accurate?

[bluesea321]

7 minutes ago, Toofarfromthesea said:

And yet you expect a puff piece aimed at the general public to be technically accurate?

 

Yes, I do expect corporate communications to be technically accurate.

[bluesea321]

Below is a video from Rai Caluori, Princess Executive Vice President of Ship Operations.  At the 1:45 minute mark he discusses air recirculation in cabins and common areas and states that their ships use a mixture of fresh and recirculated air similar to those found in hotels, resorts and casinos.   Hotels, resorts and casinos typically use a mixture of 20% fresh, 80% recirculated air, and their filters are no better than a good quality filter from Home Depot; they are not hospital quality filters.  And yes, I expect that the engineering and legal staff carefully vetted this video for accuracy prior to publication.

 

https://www.facebook.com/watch/?v=783739805479528

 

[Host Jazzbeau]

6 hours ago, bluesea321 said:

 

The document comes from RCL Corporate.  How more official can it get!!!  

 

Liberal Arts majors working in corporate are still Liberal Arts majors.

[Toofarfromthesea]

1 hour ago, Host Jazzbeau said:

 

Liberal Arts majors working in corporate are still Liberal Arts majors.

 

And chief engineers with decades of experience are still chief engineers with decades of experience.

 

And I think we can all figure out the credibility balance in that one.

[chengkp75]

12 hours ago, bluesea321 said:

 

And the above is an example of someone posting without knowing the facts.  This particular "layman" happens to be a Mechanical Engineer with a Ph.D. in Fluid and Heat Transfer and 40 years of experience on the subject so hardly a "layman" who reads something.   But I got a chuckle out of your vets' sign, good one.  🙂

My question is, in a fairly typical scenario of 55-60*F supply air, 72*F return air (to be cooled and recirculated), and 80*F outside air temperature, where is the heat sink that the heat recovery wheel uses to "catch" the heat from the return air, or is there something else it does with the heat?

Edited March 13, 2020 by chengkp75

[chengkp75]

9 hours ago, bluesea321 said:

Below is a video from Rai Caluori, Princess Executive Vice President of Ship Operations.  At the 1:45 minute mark he discusses air recirculation in cabins and common areas and states that their ships use a mixture of fresh and recirculated air similar to those found in hotels, resorts and casinos.   Hotels, resorts and casinos typically use a mixture of 20% fresh, 80% recirculated air, and their filters are no better than a good quality filter from Home Depot; they are not hospital quality filters.  And yes, I expect that the engineering and legal staff carefully vetted this video for accuracy prior to publication.

 

https://www.facebook.com/watch/?v=783739805479528

 

And, again, I have never disputed that the public spaces on ships use recirculated air.  Nor do I dispute that cabins on ships use recirculated air.  What I am clarifying is where that cabin recirculation air comes from, and where it goes to.  Does this video say anything about where?

[TravelinGert]

I hope you won't mind if I ask some questions. How is it if I open my door to my balcony and leave it open keeping my cabin door shut the entire time this affects the temperature in all the rooms around me if some of the air isn't coming from / going to other rooms? And what keeps the air in my cabin when the door is opened? Wouldn't some air then get out into the hallway?

 

Given what I know of air systems designed for hospital quarantine the answer is there is going to be some intermingling of air, surely? Definitely when the door is open and probably even when the door is closed there will be a little through the cracks. Not enough to be mentioned perhaps as it normally wouldn't matter on a ship, but still more than enough to potentially spread germs.

Edited March 14, 2020 by TravelinGert

[chengkp75]

5 hours ago, TravelinGert said:

I hope you won't mind if I ask some questions. How is it if I open my door to my balcony and leave it open keeping my cabin door shut the entire time this affects the temperature in all the rooms around me if some of the air isn't coming from / going to other rooms? And what keeps the air in my cabin when the door is opened? Wouldn't some air then get out into the hallway?

 

Given what I know of air systems designed for hospital quarantine the answer is there is going to be some intermingling of air, surely? Definitely when the door is open and probably even when the door is closed there will be a little through the cracks. Not enough to be mentioned perhaps as it normally wouldn't matter on a ship, but still more than enough to potentially spread germs.

As noted previously, 20% of the air volume of your cabin is supplied as cooled outside fresh air (taken directly from a vent on the side of the ship) per minute.  Also, 20% of the air volume, per minute, is removed from the cabin by the bathroom exhaust fan, which goes outside the ship through a vent up high on the ship.  This bathroom exhaust fan draws air from the bathroom, which then draws air from the cabin via the gap under the bathroom door.  Now, both of these systems, the fresh air supply and the exhaust air, use fans that  either supply air to, or draw air from many cabins, but note that they either get air from the outside or deliver the air to the outside, so no mingling of this air.

 

Now, as a safety measure, the bathroom exhaust fan draws out a little less air than the fresh air supply sends in, so that your cabin is at a slightly higher pressure than either the outdoors, or the passageway, and this is so that air will flow from your cabin under the door at all times it is closed, or through the open door, to keep smoke from entering your cabin in case of a fire.  There is always air flow from your cabin.  The passageway, as a public space has it's own 3 systems of ventilation, just like your cabin (fresh air supply, recirculation, and exhaust), but here the exhaust fan draws more air out of the passageway than the fresh air supplies, keeping the passageway at a slightly lower pressure than the cabins.  As I've said, public spaces recirculate the air in that space, and since the public spaces generally are open to one another, there is mingling of air between the systems in public spaces.  Each ship is divided into "vertical fire zones" which are segments of the ship delineated by the fire doors in the passageways, and these doors are in vertical alignment from top to bottom of the ship, so that closing the doors can contain a fire within that vertical section of the ship, top to bottom.  Each vertical fire zone has its own 3 ventilation systems, supplying cabins and public spaces in just that zone.  But, with the fire doors open, there will be mingling of air between systems in public spaces.

 

This is one reason the passengers onboard are kept in their cabins, and not allowed in public spaces much, because the air in those public spaces is recirculated, and there is nothing that can be done about that and keep the ship cool.

 

Now, for the great balcony door debate.  Remember that I said the fresh air supply to your cabin keeps the cabin at a higher pressure than outdoors?  Okay, that is designed with only the known gap under the door and the bathroom exhaust (both of which are known sizes) as the outlets.  Opening the door to the passageway is expected, but it is of limited time, so the system can quickly rebuild the pressure in the cabin.  Now, if you open the balcony door, and leave it open, instead of having to squeeze out under the door, the air pressure in your cabin will flow out the large area of the balcony door opening and drop the pressure in your cabin to outdoor pressure.  Now, as I said, the fresh air supply fan supplies air to many cabins (30-50, usually all the cabins on one or two decks, in a single fire zone), so if it has 29 cabins at a higher pressure, and one cabin at a lower pressure, where will the air want to flow?  The path of least resistance, and more fresh air than designed will flow to your cabin trying to rebuild the pressure.  What does that do?  It means that the other 29 cabins get less cool, fresh air, and will start to warm up, despite the actions of the in-cabin air coolers, since they are now operating outside of design parameters.

 

So, to sum up.  

 

Public spaces:  some fresh air supply, some stale air exhaust, some recirculation of air from the space (restaurant, galley, bar, passageway, etc) with some mingling of air from other spaces.

 

Cabins:  some fresh air supply, some stale air exhaust, and recirculation of the air within the cabin via a fan, cooler, and ducting within that cabin that is controlled by the cabin thermostat.

[ferring]

No matter which cruise we go on I always come home with a cold. Last Christmas we went on a Cunard cruise to the Canaries. One island we visited we had to use the shuttle bus. Most of the passengers seemed to be coughing or spluttering. I just knew I would catch something and sure enough I developed  a throat infection. I hadn’t felt so poorly for a long time. I am not sure if I caught it on the bus or through the ship‘s air conditioning. I was wondering if anyone knows how clean the air conditioning is on cruise ships. Do they regularly change the filters? I always imagined they were the cause paticulaly recently with COVID-19 when so many passengers fell ill. The reason I ask is we have a couple of cruises booked for later in the year. My wife is on the extremely vulnerable list and we have self isolated. I’m concerned about taking these cruises in case we catch the virus through the air conditioning.

[Host Kat]

17 minutes ago, ferring said:

No matter which cruise we go on I always come home with a cold. Last Christmas we went on a Cunard cruise to the Canaries. One island we visited we had to use the shuttle bus. Most of the passengers seemed to be coughing or spluttering. I just knew I would catch something and sure enough I developed  a throat infection. I hadn’t felt so poorly for a long time. I am not sure if I caught it on the bus or through the ship‘s air conditioning. I was wondering if anyone knows how clean the air conditioning is on cruise ships. Do they regularly change the filters? I always imagined they were the cause paticulaly recently with COVID-19 when so many passengers fell ill. The reason I ask is we have a couple of cruises booked for later in the year. My wife is on the extremely vulnerable list and we have self isolated. I’m concerned about taking these cruises in case we catch the virus through the air conditioning.

 

@ferring

 

Howdy & welcome to posting on the Cruise Critic message boards!  

 

To help you out I have merged your thread into one of the previous threads concerning your topic. We have trusted members that have discussed this many times. Hopefully this thread will be helpful information for your situation.

 

Please remember the following stated in the Guidelines we all agreed to follow when registering for our free memberships:

 

Browse Before You Post
Browse a topic first to see if your question has already been asked or answered by someone else. Also, many of the major cruise lines forums have a FAQ (Frequently Asked Question) topic that has been created by our members. Give that a try first. Browsing is your #1 best resource! Please post your messages in an appropriate topic so that you'll receive the best possible response. It is very time consuming to move misplaced messages that are in the wrong topics.

 

Again, I sincerely hope this will be helpful and glad to have you aboard the Cruise Critic message board! 

 

Happy sails,

 

Host Kat 

[mom says]

21 minutes ago, ferring said:

No matter which cruise we go on I always come home with a cold. Last Christmas we went on a Cunard cruise to the Canaries. One island we visited we had to use the shuttle bus. Most of the passengers seemed to be coughing or spluttering. I just knew I would catch something and sure enough I developed  a throat infection. I hadn’t felt so poorly for a long time. I am not sure if I caught it on the bus or through the ship‘s air conditioning. I was wondering if anyone knows how clean the air conditioning is on cruise ships. Do they regularly change the filters? I always imagined they were the cause paticulaly recently with COVID-19 when so many passengers fell ill. The reason I ask is we have a couple of cruises booked for later in the year. My wife is on the extremely vulnerable list and we have self isolated. I’m concerned about taking these cruises in case we catch the virus through the air conditioning.

Suggest you read the informative post above yours by our esteemed ships engineer. You are more likely to catch a respiratory infection such as COVID 19 by aerosolized droplets from other cruisers in your near vicinity. If your wife is highly vulnerable you should be reconsidering putting her into ANY environment where social distancing is a possible concern - cruise or otherwise.

[chengkp75]

30 minutes ago, ferring said:

No matter which cruise we go on I always come home with a cold. Last Christmas we went on a Cunard cruise to the Canaries. One island we visited we had to use the shuttle bus. Most of the passengers seemed to be coughing or spluttering. I just knew I would catch something and sure enough I developed  a throat infection. I hadn’t felt so poorly for a long time. I am not sure if I caught it on the bus or through the ship‘s air conditioning. I was wondering if anyone knows how clean the air conditioning is on cruise ships. Do they regularly change the filters? I always imagined they were the cause paticulaly recently with COVID-19 when so many passengers fell ill. The reason I ask is we have a couple of cruises booked for later in the year. My wife is on the extremely vulnerable list and we have self isolated. I’m concerned about taking these cruises in case we catch the virus through the air conditioning.

As Host Kat has said, I've answered the question about the HVAC systems on cruise ships many times, including on this thread.  CDC and WHO do not have any evidence of covid being transmitted via AC ducts either on cruise ships or on land.  The main reason for the severity of the number of cases of covid on cruise ships is merely the length of contact (many days) in a close environment.

 

One major cause of URI (coughs, colds) from cruise ships is not directly from the AC systems, it is a side effect.  The low humidity of the air conditioned air tends to dry out your nasal mucus membranes, which are the first and best line of defense against airborne pathogens.  A recommended solution is to use a saline nasal spray daily to keep the mucus membranes moist and working.

[Mike981]

4 minutes ago, chengkp75 said:

One major cause of URI (coughs, colds) from cruise ships is not directly from the AC systems, it is a side effect.  The low humidity of the air conditioned air tends to dry out your nasal mucus membranes, which are the first and best line of defense against airborne pathogens.  A recommended solution is to use a saline nasal spray daily to keep the mucus membranes moist and working.

 

Thank you for this. I was told it many years ago, but forgot.

I believe many people do not look at the whole picture of possibilities where they could have been infected. Like getting worn down before they travel and being more susceptible. Did they fly? If they drove, did they stop to eat, get gas and use a restroom, stay in a hotel and so on.

That said, yes I believe you can get sick from being on a cruise.

[SRF]

Bottom line is, the ONE reason you get sick.......

 

 

 

 

 

 

Is because you are ALIVE.   As long as you live, you are subject to getting sick.