The spread of aerosol particles between spaces on a cruise ship, through the ventilation system on board, is “undetectable” on surfaces and in the air.
That’s according to a new study conducted by a team of researchers from the University Of Nebraska Medical Center, in collaboration with Royal Caribbean Group.
Five medical scientists from UNMC, led by Josh Santarpia, PhD., an associate professor of pathology and microbiology at the school, conducted the study onboard Oasis of the Seas in July 2020. The team undertook the study to understand what role HVAC systems play in spreading airborne particles on cruise ships, including across staterooms, lounges, and other public spaces.
To do so, the team released billions of microspheres, simulating COVID-19 particles, across the ship. They then looked at how different airflow—when hallway and balcony doors were open, between separate public spaces, and in singular spaces—influenced the spread.
According to the study, “no exchange of aerosol particles were observed between spaces only connected by the ventilation system (such as adjacent staterooms, both crew and guests), indicating that the likelihood of aerosol exchanged between adjacent rooms is very unlikely.”
In public spaces, “test aerosol appeared to move directly between the connected spaces (outside of the ventilation systems), as expected, but smoke control systems in the public areas appear to impact the transport.”
Those spaces equipped to manage tobacco smoke (the ship’s casino and comedy club) were able to contain the particles largely contained within those areas. In the other public spaces that don’t allow smoking, like the ice skating rink, particles spread to the adjacent comedy club “likely due to the smoke control system in that space” but the no-smoking lounge adjacent to both the comedy club and ice rink had no spread.
“In general, particles released in the public areas were not observable after 15 minutes, likely due to dilution in the large spaces.”
The UNMC team worked with Royal to adjust some of the ships setting to “allow for the maximum air changes per hour” and recommended upgrading to MERV 13 filters throughout the systems and HEPA filters in the medical facility to limit the spread even further.
The upgrades were part of the recommendations that were made by Royal and Norwegian Cruise Lines’ Healthy Sail Panel last year.
“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.”
Here's how that system works, according to Royal: