Royal Caribbean Study: Transmission of Aerosol Particles Through HVAC Is Low

Scientists have found transmission of aerosol particles through a modern cruise ship's heating, ventilation and air-conditioning system (HVAC) system is exceptionally low and undetectable both in the air and on surfaces. That's the top finding from a July 2020 study conducted onboard Royal Caribbean International's Oasis of the Seas by the University of Nebraska Medical Center (UNMC) and the National Strategic Research Institute (NSRI).

In addition, the scientific study found that "no exchange of aerosol particles was observed between spaces only connected by the ventilation system (such as adjacent staterooms, both crew and guest), indicating that the likelihood of aerosol exchange between adjacent rooms is very unlikely."

In public areas, test aerosol appeared to move directly between the connected spaces (outside of the ventilation systems), as expected, but smoke control systems in some public areas appear to impact the transport. Aerosol released in areas equipped to manage tobacco smoke (such as the casino and comedy club) were largely contained within those.

Commissioned by Royal Caribbean Group, the study on one of the world's largest cruise ships was designed to understand the role of ship ventilation systems in the spread of airborne diseases such as COVID-19. It also provided a scientific basis for changes to shipboard operation to minimize the spread of disease.

Examining Air Flow

A team of five medical scientists specializing in bioaerosols conducted the study. That team was led by Josh Santarpia, PhD., associate professor, pathology and microbiology, UNMC, and research director, chemical and biological programs, NSRI. Consisting of nine experiments, the study was conducted onboard Oasis of the Seas, while the vessel was berthed in Miami. The scientists examined the effectiveness and efficiency of ship air management strategies—ventilation, filtration and supply—as well as air flow across different areas of the ship including guest staterooms, crew staterooms, lounges and other public spaces. 

Study findings then were used by experts serving on the Healthy Sail Panel, a joint effort of Royal Caribbean Group and Norwegian Cruise Line Holdings, in developing 74 best practices for a healthy return to sailing. Those were submitted in September 2020 in response to a U.S. Centers for Disease Control and Prevention (CDC) request for public comment.

Royal Caribbean Group said in a press statement about the research results that its "existing HVAC systems were created to be robust and efficient in providing maximum ventilation, continual fresh air intake and layers of filtration for both incoming and outgoing air."

That said, based on study findings and at the recommendation of the Healthy Sail Panel, Royal Caribbean Group is adopting several new practices and incorporating additional layers of protection that further minimize the possibility of spread: It's adjusting shipboard settings to allow for the maximum air changes per hour and is upgrading to MERV (Minimum Efficiency Reporting Value) 13 filters throughout the system. In addition, Royal Caribbean Group has already equipped its medical facilities with an independent ventilation system and has added HEPA filters for additional precaution.

Source: Royal Caribbean Group

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