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What You Need To Know Your Cruise Ship’s HVAC System

PortandTerminal.com, September 23, 2020

Be sure to ask about the MERV Rating of the filters the HVAC system on your cruise ship uses before you book your next trip – it may save your life.

MIAMI – Cruise Lines International Association (CLIA), which represents 95% of global ocean-going cruise capacity, announced on Monday the adoption of a set of health protocols to be implemented as part of a phased-in, controlled resumption of operations. 

The cruise industry is on its knees and desperately needs a resumption of cruising as soon as possible. Cruise lines are cutting staff, selling ships and bleeding money.

Cruising out of US ports is currently banned through a No Sail Order from the US Centers for Disease Control and Prevention (CDC) until at least October 31.

CLIA’s hope is that by adopting these health protocols proposed by their Healthy Sail Panel that they can convince the CDC to lift its No Sail Order and get cruise companies back in business ASAP – ideally before the end of 2020.

Health Protocols

CLIA’s “Healthy Sail Panel” has outlined in their report dated September 21, 2020 health protocols they believe will make it safe to cruise again. These include some very sensible measures such as the testing of all guests and crew for infection prior to boarding, the mandatory wearing of masks when social distancing is impractical and so on. You can read the full 65 page report by clicking here.

One important area the report goes into is the role cruise ship HVAC systems (heating, ventilation and air conditioning) play in controlling the spread of COVID-19. But before we talk about HVAC systems we need to discuss two important things. The first is the “Airborne Transmission of COVID-19”. The second is “MERV Ratings on HVAC Filters”.

HVAC system onboard the cruise ship MSC Meraviglia
The HVAC system onboard the cruise ship MSC Meraviglia

Airborne Transmission of COVID-19

COVID-19 can spread in a number of different ways. Close personal contact with infected people via mouth and nose secretions was thought to be the dominant mode of infection.

Emerging data have also implicated the tiny particles emitted when an infected person speaks, sings or even just breathes normally. CLIA’s “Healthy Sail Panel” highlight this on page 34 of their report and in their recommendations:

“Recommendation 29: Transmission of SARS-CoV-2 through the air is sufficiently likely that airborne exposure to the virus should be controlled for.”

CLIA’s report sites a study on airborne transmission of virus like material conducted recently by The University of Nebraska Medical Center & National Strategic Research Institute. The institute’s study was conducted on Royal Caribbean’s “Oasis of the Seas” vessel.

The Healthy Sail Panel sites two important findings from the the study on page 35 of its report:

  1. Unpublished data from this assessment highlights that an HVAC system equipped with MERV 13 filtration and an energy recovery wheel did not transport a significant number of aerosols into adjacent rooms and spaces served by the same air handling unit, and in most cases the airborne contamination was undetectable”.
  2. “In public areas, guest staterooms, and crew cabins, airborne contamination disappeared or microspheres were not detectable in less than an hour from the space they were released”.

Let’s simplify this into plain language because both points are important.

First, The Healthy Sail Panel says that unpublished data from the study suggests that COVID-19 isn’t spread through ships by the air-conditioning units on-board. Why the data is unpublished is unclear but let’s take it at face value for now.

Their second point is that after about an hour the little virus droplets in the air are gone. Or put in another more alarming way, the virus and associated risk of infection linger in the air for up to an hour.

Which brings us to our next point. The University of Nebraska Medical Center study found that to clear the virus droplets from the air in about an hour they needed to use an HVAC system that changed the air in the room at least 6 times or more and used a filter with a MERV rating of 13.

“This was accomplished by the combination of ≥ 6 air changes in the room and filtration of air through the MERV 13 filters.”

As we will see below, filters with a MERV rating of 13 are hospital grade filters. Unfortunately, not all cruise ships have HVAC systems that can accommodate such high grade filters.

MERV Ratings on HVAC Filters

Air filter
An air filter’s ability to trap particles in measured by its MERV Rating which range from 1 to 20. The higher the MERV rating, the higher the air filtration capabilities of a particular filter. A filter with a MERV rating of 13-16 is considered hospital level air quality.

MERV stands for Minimum Efficiency Reporting Value, a system used to evaluate the efficiency of an air filter based on how effective it is at catching particles of various sizes.

The higher the MERV rating, the higher the air filtration capabilities of a particular filter. MERV ratings range from 1-20, with 1 being the lowest level of filtration and 20 being the highest.

The higher the MERV rating the smaller the particles the filter is able to remove from the air. A MERV rating of 13-16 is considered hospital level air quality.

MERV rating chart

HVAC Systems on Cruise Ships

As we saw earlier, the University of Nebraska study’s conclusions were based upon an HVAC system that used air filters with a MERV 13 rating.

But, as CLIA’s Healthy Sail Panel acknowledge in their report, not all cruise ships have HVAC systems that can accommodate the MERV 13 filters. Some HVAC systems on ships are designed to take only up to MERV 8 filters. Why? The higher the MERV rating the harder an HVAC system needs to work to pull air through it – not all are designed to work that hard.

To use an analogy, your lungs need to work harder to breathe through a piece of thick wool blank placed over your nose and mouth than they do through a piece of flimsy cheese cloth. Thick wool blankets have a higher MERV rating than flimsy cheese cloth in this analogy.

“The Panel understands that ships vary in age, size, layout, ventilation type, etc. (sometimes significantly). As such, the Panel did not feel comfortable recommending minimum levels of protection for each air management strategy.

However, the Panel does feel strongly that MERV 13 HVAC filters should be utilized. If that is infeasible, the Panel strongly believes that cruise operators should optimize the air management strategies used to the greatest extent possible on each of their ships, which would include upgrading HVAC filtration to as close to a MERV 13 filter as possible.”

So the bottom line is this. The Healthy Sail Panel has outlined some very good measures to make it safe to cruise again. What they can’t control for though are the HVAC systems installed on each of the hundreds of cruise ships out there.

So as a consumer, when you book your next cruise it’s up to you to be sure that your vessel has an HVAC system that uses MERV 13 filters. Ask.

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