Expected changes when cruises resume

[Starwind]

Posted same in another thread:

I wonder if someone will make it mandatory or if cruise lines will voluntarily make changes to the A/C systems so they are more hygenic. If I recall, one of the problems on the current ships is that, unlike an airplane, the air just recirculates, which is a perfect storm for spreading an airborne virus. It may happen via drydocks, or it may become a condition of being allowed to sail from specific ports, but I bet something will have to happen and that's going to be a big expense.

One of the things that came to light with the Diamond Princess situation is that normally at least on that ship, but apparently on most cruise ships, is that passenger cabin air is about a 50/50 mix of recycled air and fresh external/outside air. On the Diamond Princess, your room air is pulled into the hallway outside your room, where it circulates with the air from the hallway and thus also other rooms along that hallway, and the is pulled into the ventilation system where it is recirculated in a 50/50 mix with air pulled from outside the ship.

Some time into the DP's outbreak/quarantine period they realized this *may* be a contributing factor, so they switched the flow to 100% fresh outside air going into passenger cabins. [as an aside, good to know they have the ability to do this "on the fly" without major re-engineering, it already exists as an option, at least for some ships]].

The Genting cruise line in their announcement of the preventive measures they will be taking when they reopen, speak to changes to ventilation [source: http://gentingcruiselines.com/media...rds-for-the-fleet-and-the-cruise-industry.pdf ]:



I would expect to see changes to the ventilation systems on cruise ships with a shift to 100% filtered external air [as with Genting, as with what DP ended up doing] as well as with the use of high filtration systems [eg HEPA where feasible] and possibly the use of different types of UV or other systems [if there is good science evidence to demonstrate their utility against covid-19's coronavirus] as scientifically appropriate for both ventilation systems as well as for indoor spaces. Part of the challenge is going to be is what science evidence is there and is it strong enough ?

There are also going to be some challenges to grapple with and lessons to be learned, extrapolated from, experimented with, studied some more, and implemented. For example, this case study of a restaurant outbreak in China: https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article "Abstract: During January 26–February 10, 2020, an outbreak of 2019 novel coronavirus disease in an air-conditioned restaurant in Guangzhou, China, involved 3 family clusters. The airflow direction was consistent with droplet transmission. To prevent the spread of the virus in restaurants, we recommend increasing the distance between tables and improving ventilation." This has clear implications for something like a cruise ships and its dining locations and at the very least needs some more study.

An interesting little article about air handler systems in cruise ships, form a manufacturer: https://www.systemair.com/gb/support/good-to-know/ventilation-in-cruise-ships/

I wonder if by running them at 100% external air they run into an issue of corossion/more maintenance and end up having to replace them sooner ? Perhaps there isn't a massive up front cost, but in the long run there would be more cost as you would have to replace them more often because you are running salt air through them at a much higher rate than "normal" ?

This article has an interesting interview with a mechanical engineer about ventilation systems on cruise ships and comparing it to the two Navy hospital ships as well as implications for cruise ships going forward: https://www.businessinsider.com/are-hospital-ships-safe-given-what-weve-seen-on-cruise-ships-2020-3

Finally, at least one post-DP study has suggested, as noted in this media report, that the DP's ventilation system may not have played a role in the spread of the virus on board: https://nationalpost.com/opinion/co...from-the-cruise-ship-that-sailed-into-history If subsequent studies determine that is in fact the case, then it will be interesting to see what the cruise ships choose or are required to do -- will they shift stateroom ventilation anyway ?

SW

 

[wombat_5606]

One of the things that came to light with the Diamond Princess situation is that normally at least on that ship, but apparently on most cruise ships, is that passenger cabin air is about a 50/50 mix of recycled air and fresh external/outside air. On the Diamond Princess, your room air is pulled into the hallway outside your room, where it circulates with the air from the hallway and thus also other rooms along that hallway, and the is pulled into the ventilation system where it is recirculated in a 50/50 mix with air pulled from outside the ship.

Some time into the DP's outbreak/quarantine period they realized this *may* be a contributing factor, so they switched the flow to 100% fresh outside air going into passenger cabins. [as an aside, good to know they have the ability to do this "on the fly" without major re-engineering, it already exists as an option, at least for some ships]].

The Genting cruise line in their announcement of the preventive measures they will be taking when they reopen, speak to changes to ventilation [source: http://gentingcruiselines.com/media...rds-for-the-fleet-and-the-cruise-industry.pdf ]:

View attachment 494234

I would expect to see changes to the ventilation systems on cruise ships with a shift to 100% filtered external air [as with Genting, as with what DP ended up doing] as well as with the use of high filtration systems [eg HEPA where feasible] and possibly the use of different types of UV or other systems [if there is good science evidence to demonstrate their utility against covid-19's coronavirus] as scientifically appropriate for both ventilation systems as well as for indoor spaces. Part of the challenge is going to be is what science evidence is there and is it strong enough ?

There are also going to be some challenges to grapple with and lessons to be learned, extrapolated from, experimented with, studied some more, and implemented. For example, this case study of a restaurant outbreak in China: https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article "Abstract: During January 26–February 10, 2020, an outbreak of 2019 novel coronavirus disease in an air-conditioned restaurant in Guangzhou, China, involved 3 family clusters. The airflow direction was consistent with droplet transmission. To prevent the spread of the virus in restaurants, we recommend increasing the distance between tables and improving ventilation." This has clear implications for something like a cruise ships and its dining locations and at the very least needs some more study.

An interesting little article about air handler systems in cruise ships, form a manufacturer: https://www.systemair.com/gb/support/good-to-know/ventilation-in-cruise-ships/

I wonder if by running them at 100% external air they run into an issue of corossion/more maintenance and end up having to replace them sooner ? Perhaps there isn't a massive up front cost, but in the long run there would be more cost as you would have to replace them more often because you are running salt air through them at a much higher rate than "normal" ?

This article has an interesting interview with a mechanical engineer about ventilation systems on cruise ships and comparing it to the two Navy hospital ships as well as implications for cruise ships going forward: https://www.businessinsider.com/are-hospital-ships-safe-given-what-weve-seen-on-cruise-ships-2020-3

Finally, at least one post-DP study has suggested, as noted in this media report, that the DP's ventilation system may not have played a role in the spread of the virus on board: https://nationalpost.com/opinion/co...from-the-cruise-ship-that-sailed-into-history If subsequent studies determine that is in fact the case, then it will be interesting to see what the cruise ships choose or are required to do -- will they shift stateroom ventilation anyway ?

SW

I follow a gentleman on another board and he is a former cruise ship Chief Engineer, but not on DCL. Obviously many people are discussing this situation and he has provided this information. Now, maybe different cruise ships do different things, but this is his experience on the cruise ships he has worked on.

Cabins do recirculate air, but only within that cabin, much as your window AC unit recirculates air within the room it is in.

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.

This selection below explains how propping your balcony door is a bad thing.

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.