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There’s nothing like breathing fresh air while cruising the open ocean. But what happens once you step inside a cruise ship – how does the air flow into your stateroom, restaurant and other spaces on board? This is what Royal Caribbean Group wanted to confirm and understand in detail.
Enter the University of Nebraska Medical Center (UNMC) and National Strategic Research Institute (NSRI), at the recommendation of the Healthy Sail Panel, globally recognized experts in medical practice and research, public health, infectious diseases, biosecurity, hospitality and maritime operations commissioned by Royal Caribbean Group and Norwegian Cruise Line Holdings to recommend the most effective, scientifically sound ways to make the cruise experience healthier and safer. The team from UNMC and NSRI, which specializes in bioaerosols (the study of airborne particles) and more recently worked with the U.S. Department of Defense on the study of air flow on planes, boarded Oasis of the Seas in July 2020 with the objective of understanding the ins-and-outs of air flow on a Royal Caribbean cruise ship.
Dr. Josh Santarpia, PhD, associate professor at the University of Nebraska and research director at the National Strategic Research Institute, and the study’s lead scientist, helped establish the objective, “the predominant goal of the study was to try to understand the role of HVAC (heating, ventilation and air conditioning) in spreading particulate matter on a cruise ship, identifying a pattern and how quickly it’s filtered out.”
The independent assessment called for billions of microspheres – simulating SARS-CoV-2 aerosols – to be released in separate locations across the ship. The scientists set out to determine the efficiency and effectiveness of the ship’s air management as well as understand how aerosols pass through the HVAC system. They carefully studied the air flow under several scenarios: when hallway and balcony doors were open and closed, between adjacent private spaces i.e., guest and crew staterooms, between separate public spaces, such as the casino, restaurants and lounges; as well as within a singular space.
The microspheres used in this study are spherical particles made of a plastic polymer that are coated with unique DNA barcodes so that they can be easily detected.
The teams’ work confirmed that the existing system’s air handling units reduce the transmission of aerosol particles between spaces, so much so that it’s exceptionally low and undetectable on surfaces and in the air in most test cases. This is thanks to the robust and efficient system originally designed into the ship for maximum ventilation, continual fresh air intake and filtration. To add layers of safety and further minimize the possibility of spread, the team from UNMC and NSRI recommended adjusting shipboard settings to allow for the maximum air changes per hour and upgrading to MERV 13 filters throughout the system. In the medical facility, already equipped with an independent ventilation system, HEPA filters have been added for extra precaution.
The MERV rating of a filter refers to how much it can filter particles in the air, with a higher number meaning a higher level of filtration. A MERV rating of 13 is considered hospital-level air quality. MERV-13 captures aerosols 1 to 3 microns in size with 90% efficacy— fine enough to filter colds, flu germ and coronavirus.
“Our existing HVAC system is designed with several layers to continuously bring in the ocean air and filter it multiple times before it reaches our guests and crew. We are glad to see the study conclude that our robust system is effective in reducing transmission,” said Patrik Dahlgren, Royal Caribbean Group’s senior vice president of Global Marine Operations and a member of the Healthy Sail Panel. “By taking a scientific approach and implementing recommendations made by the experts at University of Nebraska Medical Center and the National Strategic Research Institute, we’ve created an environment that is even safer for our guests and crew. And we’ve done so without compromising their comfort – which is always front of mind because this is our guests’ vacations and our crew’s home at sea.”
Upgrading HVAC systems was among the critical recommendations made to the cruise industry by the Healthy Sail Panel. The robust set of measures put forth by the panel and adopted by the cruise industry as a whole is rooted in science, data-driven and developed with guidance from specialists, such as UNMC’s bioaerosol team, public health authorities around the world and Royal Caribbean Group’s Chief Medical Officer, Dr. Calvin Johnson.
How does the system work?
Air filtration
The HVAC systems on Royal Caribbean Group ships have frequent layers of filtration. Incoming air is filtered twice when it comes into the ship, including through a MERV 13 filter. It then branches out across the ship through the system to be filtered again in local areas, say your stateroom or the theater.
Air ventilation
The ocean air is continuously drawn in from one side of the ship for cooling and ventilation as the existing air is exhausted on the opposite side of the ship. This constant intake of fresh air, combined with the other robust components of the HVAC system, allows for up to 12 air changes an hour in staterooms and 15-20 changes in public venues. This frequency is twice more than what is recommended for land-based public venues by ASHRAE, the American Society of Heating, Refrigerating and Air-Conditioning Engineers.
Air change rate is the measure of air volume added to or removed from a space in one hour, divided by the volume of the space. If the air in the space is uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced each hour.
The result of all of this focus and scientific methodology?
A fleet of ships on which our guests and crew can breathe easy.
Royal Caribbean Group is built on innovation, relentless attention to detail and commitment to exceeding guests’ expectations. With effective air management and by upgrading supply and exhaust filters to MERV 13 – coupled with everyone taking part in keeping each other as safe as possible by adopting today’s common best practices – the potential of a virus like COVID-19 spreading on board is even lower. There’s no more important investment in this ever-changing world than the health and safety of our guests, crew and the communities we visit.