Medical Grade HEPA Air Filters

[BigTimeCruiser]

I read on Cruise Industry News this morning that NCL will be installing Medical Grade H-13 HEPA air filters on their ships. I hope Princess Cruises follows suit to prevent most virus from being passed between staterooms and the hallways.  https://www.cruiseindustrynews.com/cruise-news/23033-norwegian-cruise-line-releases-new-health-protocols.html

[cruisequeen4ever]

If Princess doesn’t already have them, I hope so, too! I thoughtttttt I read back during the Diamond Princess crisis that Princess already uses HEPA filtration but could be wrong. 

[Daniel A]

6 hours ago, BigTimeCruiser said:

I read on Cruise Industry News this morning that NCL will be installing Medical Grade H-13 HEPA air filters on their ships. I hope Princess Cruises follows suit to prevent most virus from being passed between staterooms and the hallways. 

A very knowledgeable person with maritime experience posted this week that cabin air is not circulated with other cabins (and from the description, sounds like the hallways too.)  The description was that the each cabin's air comes in from the outside and exits via the bathroom vent.  The HEPA filters might come in handy for larger venues like the dining rooms and theater and lounges.

[Sam Ting]

1 hour ago, Daniel A said:

A very knowledgeable person with maritime experience posted this week that cabin air is not circulated with other cabins (and from the description, sounds like the hallways too.)  The description was that the each cabin's air comes in from the outside and exits via the bathroom vent.  The HEPA filters might come in handy for larger venues like the dining rooms and theater and lounges.

Yeah right.  How does he think all those poor people got it then?  Hugging and kissing their fellow quarantined passengers when nobody was looking?  A little knowledge is dangerous.  The director of operations had it right.

[Daniel A]

14 minutes ago, Sam Ting said:

Yeah right.  How does he think all those poor people got it then?  Hugging and kissing their fellow quarantined passengers when nobody was looking?  A little knowledge is dangerous.  The director of operations had it right.

Don't shoot the messenger...  I don't make the news, I just reported it.   ☺️

 

BTW, who is the "director of operations??"

Edited June 2, 2020 by Daniel A

[mk-ultra]

16 minutes ago, Sam Ting said:

Yeah right.  How does he think all those poor people got it then?  Hugging and kissing their fellow quarantined passengers when nobody was looking?  A little knowledge is dangerous.  The director of operations had it right.

 

Air is NOT circulated between cabins. Can you imagine how disastrous that would be with a cabin fire?

 

Sure, if you open your door you're going to get some mixing from the hallway.

 

Your cabin air is recirculated in your cabin, with a ~20% mix of outside "fresh" air not drawn from other cabins or shared spaces.  It's a one-way system that keeps your cabin under slight positive pressure (to keep smoke out if there is a fire) and exits through the vent in your bathroom.

 

 

[npcl]

8 hours ago, BigTimeCruiser said:

I read on Cruise Industry News this morning that NCL will be installing Medical Grade H-13 HEPA air filters on their ships. I hope Princess Cruises follows suit to prevent most virus from being passed between staterooms and the hallways.  https://www.cruiseindustrynews.com/cruise-news/23033-norwegian-cruise-line-releases-new-health-protocols.html

Hate to tell you, but the filters would not help.  The air flow into cabins is such that the air flows from the cabin into the hall way. So if you have some one in in a cabin, and airborne virus will naturally flow into the hallway, without ever going through a filter.

 

Air flow in via AC vent, flow out via exhaust vent in bath room, and out into hallway. The air flow is intentionally set up that way to keep the room slightly positive pressure to the hall. Unless, of course, you leave your balcony door open.

[npcl]

2 hours ago, Daniel A said:

A very knowledgeable person with maritime experience posted this week that cabin air is not circulated with other cabins (and from the description, sounds like the hallways too.)  The description was that the each cabin's air comes in from the outside and exits via the bathroom vent.  The HEPA filters might come in handy for larger venues like the dining rooms and theater and lounges.

Does not circulate between cabins but the normal air flow is a/c vent to cabin, then out exhaust vent in bathroom and out into hallway. More air comes in via A/C vent then leaves via bath vent. rest goes to hallway. This has been described several time by chengkp75.

[npcl]

58 minutes ago, Sam Ting said:

Yeah right.  How does he think all those poor people got it then?  Hugging and kissing their fellow quarantined passengers when nobody was looking?  A little knowledge is dangerous.  The director of operations had it right.

If you read the reports from the analysis of the Diamond incident.

 

1. Most passengers were infected prior to quarantine initiation. (they have a complete schedule of anyone that developed symptoms or tested positive compared to the normal incubation schedule, rooms locations, etc.)

2. The  passengers that were infected during quarantine were those that were sharing cabins with someone already infected.

3. The crew had some infected prior to quarantine, but continued to get infected during quarantine, because they were not isolated, they continued to work together,  they ate in the close in crew dining area and there was some issues with how their PPE was used.

 

There are some very good reports from the Japanese institute of infectious disease.  Also there is a video documentary from NHK, that shows the detail in which the incident was analysed, including cabin maps of all crew and passengers that were infected.

[chengkp75]

And, while the air in public spaces is recirculated, including the hallways, there is no clinical data that I am aware of that shows that transmission via AC ducts is viable.  The distance is just too far for droplet concentrations to carry, and the air velocity is so low that the virus will drop out of suspension long before it can make the return journey from AC vent to air handler and back to AC vent.  The only study that I have seen regarding AC and covid transmission deals with the airflow from an AC vent carrying a sneeze further than the sneeze would have carried, but does not say that even in a relatively small space like a land restaurant that the virus was transmitted via recirculated air.

[Ken the cruiser]

27 minutes ago, chengkp75 said:

And, while the air in public spaces is recirculated, including the hallways, there is no clinical data that I am aware of that shows that transmission via AC ducts is viable.  The distance is just too far for droplet concentrations to carry, and the air velocity is so low that the virus will drop out of suspension long before it can make the return journey from AC vent to air handler and back to AC vent.  The only study that I have seen regarding AC and covid transmission deals with the airflow from an AC vent carrying a sneeze further than the sneeze would have carried, but does not say that even in a relatively small space like a land restaurant that the virus was transmitted via recirculated air.

Setting COVID aside for a second, what particulates (if you know) would these medical grade HEPA filters help filter out that the normally installed filters simply allow to pass through. For example, could they stop mold spores?

Edited June 3, 2020 by Ken the cruiser

[neverbeenhere]

Hepa filter remove pollens, but not molds, bacterias,  viruses,  and not the occasional pesky  neighbor.  

Edited June 3, 2020 by neverbeenhere

[Steelers36]

I am no HVAC pro (wouldn't call myself an amateur even 😉 ), but if a bunch of HEPA filters were installed in a HVAC system, would that affect airflow and perhaps end up requiring stronger fans in order to push and circulate the same amount of air?

[caribill]

14 hours ago, BigTimeCruiser said:

I read on Cruise Industry News this morning that NCL will be installing Medical Grade H-13 HEPA air filters on their ships. I hope Princess Cruises follows suit to prevent most virus from being passed between staterooms and the hallways.  https://www.cruiseindustrynews.com/cruise-news/23033-norwegian-cruise-line-releases-new-health-protocols.html

 

ALL-NEW AIR FILTRATION

Installation of medical-grade air-filters, H13 HEPA, that remove 99.95% of airborne pathogens across our entire fleet to ensure the air you breathe is clean.

• Replace existing filters with H13 HEPA filters – Medical Grade
  H13 HEPA is one of the highest grades of particulate air filter, removing 99.95% of all particulates 0.1 microns or larger. For comparison purposes, COVID-19 is 0.125 microns (25% larger), a single blood cell is 10 microns (10,000% larger) and a single human hair is 75 microns (75,000% larger).

[brisalta]

49 minutes ago, caribill said:

 

ALL-NEW AIR FILTRATION

Installation of medical-grade air-filters, H13 HEPA, that remove 99.95% of airborne pathogens across our entire fleet to ensure the air you breathe is clean.

• Replace existing filters with H13 HEPA filters – Medical Grade
  H13 HEPA is one of the highest grades of particulate air filter, removing 99.95% of all particulates 0.1 microns or larger. For comparison purposes, COVID-19 is 0.125 microns (25% larger), a single blood cell is 10 microns (10,000% larger) and a single human hair is 75 microns (75,000% larger).

 

 I just read an article regarding filters and according to that H13 filters are middle of the road and do not filter out very small particles such as viruses to any extent that would be significant. It seems NCL is blowing smoke. They would need to redesign there HVAC if they were going to filter out extremely small particles.

[chengkp75]

Let's get a few things straight, first.  A HEPA filter rating is just that, it means it was tested to a standard set by a testing agency like the ASTM, and meets that standard.  For HEPA-13 filters that is that it will attract 99.95% of particles 0.1 microns or larger. That does not mean it will not attract any particles smaller than 0.1 micron, because the HEPA filter does not rely entirely on pore size "sieving", or trapping particles between fibers.  Use of nanofibers will also attract smaller particles by the "diffusion" method as described:

 

"Diffusion Diffusion works on the smallest particles. Small particles are not held in place by the viscous fluid and diffuse within the flow stream. As the particles traverse the flow stream, they collide with the fiber and are collected."

 

HEPA filters actually "work" better, trapping more smaller particles than the rated size.

 

But, the real question is, is there actually a viral load in the air prior to going through the HEPA filter.  Does an aerosol virus travel in air, especially the slow moving air within a space before it is taken into the return air duct, far enough to actually reach the HEPA filter in the filter/fan/cooling coil air handler perhaps a couple hundred feet away?

 

HEPA filters will remove mold spores, and they will die on the filter as it is a dry environment.  HEPA filters will also filter out most bacteria.

 

HEPA filters are designed to have minimal impact on airflow, with designed amounts of backpressure, and since the systems currently have filtration in them, I don't see filter backpressure as a problem.

 

Will a HEPA filter work?  Yes.  Will a HEPA filter take out more particulates and any present pathogens than current industrial filters used on the ships?  Yes.  Is there actually a viable pathogen load entering the recirculation air handler that requires a HEPA filter?  I don't know, but neither CDC or WHO have found any evidence of covid transmission via AC ductwork, nor has the CDC required HEPA filters in the past for control of other airborne viruses like influenza on ships.

 

Bottom line, will HEPA filters actually make a difference in transmission of a virus like covid, or is it merely optics which while making air on the ships cleaner actually does nothing towards containing spread of a viral disease.  Only scientific, peer reviewed studies could answer that, and it would be very easy to get the first stage of that study done now, "is there any viral load entering the AC filters?"

[Aus Traveller]

20 hours ago, BigTimeCruiser said:

I read on Cruise Industry News this morning that NCL will be installing Medical Grade H-13 HEPA air filters on their ships. I hope Princess Cruises follows suit to prevent most virus from being passed between staterooms and the hallways.  https://www.cruiseindustrynews.com/cruise-news/23033-norwegian-cruise-line-releases-new-health-protocols.html

Air does not pass between staterooms and the hallways. The Japanese Health Ministry report on the Diamond Princess states that they believe the passengers infected with COVID-19 acquired it before the isolation procedures were in place. It is possible in a couple of cases, that crew delivering meals passed the infection and it is known that in at least one case, a health worker was infected by a passenger. I suggest you read the posts from the Chief Engineer 'cheng75' who has explained how the ventilation system works on modern ships.

 

I have been on a cruise ship where there was a lot of smoke from a fire in a cabin near ours and there was no trace of smoke in our cabin.

 

P.S. I now see that 'Cheng75' has posted an answer. I replied before reading to the last post.

Edited June 3, 2020 by Aus Traveller

[laktex]

6 hours ago, Steelers36 said:

I am no HVAC pro (wouldn't call myself an amateur even 😉 ), but if a bunch of HEPA filters were installed in a HVAC system, would that affect airflow and perhaps end up requiring stronger fans in order to push and circulate the same amount of air?

 

I'm pretty sure that HEPA filters would require a stronger air flow than non HEPA.

I do not know about ship's A/C but the use of UV C light can be used to good effect but requires careful installation - I am sure others will be able to elaborate.

 

 

[Sam Ting]

22 minutes ago, Aus Traveller said:

Air does not pass between staterooms and the hallways. The Japanese Health Ministry report on the Diamond Princess states that they believe the passengers infected with COVID-19 acquired it before the isolation procedures were in place. It is possible in a couple of cases, that crew delivering meals passed the infection and it is known that in at least one case, a health worker was infected by a passenger. I suggest you read the posts from the Chief Engineer 'cheng75' who has explained how the ventilation system works on modern ships.

 

I have been on a cruise ship where there was a lot of smoke from a fire in a cabin near ours and there was no trace of smoke in our cabin.

 

P.S. I now see that 'Cheng75' has posted an answer. I replied before reading to the last post.

Yeah okay. Maybe someone should call them up and tell them that an anonymous poster on some website has them convinced they are wasting their money. 

[Sam Ting]

4 minutes ago, laktex said:

 

I'm pretty sure that HEPA filters would require a stronger air flow than non HEPA.

I do not know about ship's A/C but the use of UV C light can be used to good effect but requires careful installation - I am sure others will be able to elaborate.

 

 

They could probably boost the fan speed if the duct size could handle it. Of course they could just leave as is and claim 80 degrees is their standard.  

[skynight]

chengkp75

Assume your normally assigned ships will now have these filters. You may actually be involved in a long term study.

Another question. Does a change HEPA filters require physical modification of the systems, or are they just remove and replace?

[chengkp75]

46 minutes ago, skynight said:

chengkp75

Assume your normally assigned ships will now have these filters. You may actually be involved in a long term study.

Another question. Does a change HEPA filters require physical modification of the systems, or are they just remove and replace?

Well, given that my normally assigned ship is a tanker and not a cruise ship anymore, it isn't likely we would go away from the commercial grade fiberglass filter to a HEPA filter.  The change to a HEPA filter depends on what type of filter is in place currently, and what type of HEPA filter is desired.  Most ships have either permanent, cleanable manually removed filters, and you can get the equivalent sized HEPA filters that can fit in place, and be replaced on either a calendar basis or using a differential pressure measurement across the filter to show its level of clogging.  The ship might have a "roll type" filter, where a continuous sheet of filter material is on a storage roll, and then goes through the air handler, and is collected on another storage roll.  Again, either on a manually selected time (calendar) or on differential pressure, a motor starts to pull the used filter onto the discard roll and new filter media is pulled into the airstream from the storage roll.  Any type of HEPA filter can be installed with minor or no modifications to the existing systems, in most cases.

[Ken the cruiser]

2 hours ago, chengkp75 said:

HEPA filters will remove mold spores, and they will die on the filter as it is a dry environment.  HEPA filters will also filter out most bacteria.

Thanks @chengkp75 for your great detailed summary!! I was hoping the HEPA filters would remove mold spores, as that seems to be a big issue on some of the older ships in the various cruise line fleets we sail on. I know COVID has been the catalyst for change, but mold has also been an issue on some of the older ships for quite some time.

[voljeep]

3 minutes ago, chengkp75 said:

Well, given that my normally assigned ship is a tanker and not a cruise ship anymore

thanks - so when was your last cruise ship assignment ?

[chengkp75]

Just now, Ken the cruiser said:

Thanks @chengkp75 for your great detailed summary!! I was hoping the HEPA filters would remove mold spores, as that seems to be a big issue on some of the older ships in the various cruise line fleets we sail on. I know COVID has been the catalyst for change, but mold has also been an issue on some of the older ships for quite some time.

I assume you have some data on mold in ships, or some anecdotal evidence, because I personally haven't seen any real evidence of it in ductwork.  In fact, the USPH requires sanitizing pads in the drain pans of air handlers to deal with just this kind of problem, molds and aerosol bacteria like legionella.  The air in the ship's AC system is low in humidity, so the only real place that mold would form is in the air handlers where the condensation forms and drains.  Studies have shown that things like "duct cleaning" services are overrated in their need and performance, and can actually cause more problems after cleanings.