
In Science of the Total Environment, a University of Surrey–led research team that measured indoor air quality (IAQ) on board a large cruise ship in August 2023 identifies crowded dining areas as priorities for improved air circulation and the prevention of disease outbreaks.
The investigators, working on the European Union’s (EU’s) HEALTHY SAILING project, monitored 24-hour indoor carbon dioxide (CO2) levels to evaluate temperature, humidity, ventilation, airborne infection risk, and energy efficiency by monitoring IAQ in three cabins and the buffet, gym, bar, restaurant, pub, and theater of a 5,000-passenger cruise ship traveling between UK and EU ports.
Airborne infection risk was calculated based on the assumption that the air contains doses of virus and that occupants are infected by inhaling a single dose. “The infected person breathes out virus-laden particles at a constant rate, and the infectious dose of the virus can be removed when it decays, falls onto a surface, or is diluted by ventilation,” the study authors wrote.
‘Hotspots for super-spreading events’
To illustrate disease risk on board cruise ships, the researchers noted the outbreak on the Diamond Princess cruise ship early in the COVID-19 pandemic. The ship was placed under quarantine at Yokohama in Japan for nearly a month, with quarantine of passengers and crew members except to perform essential tasks. The outbreak killed 13 people and resulted in 712 infections.
“The COVID-19 pandemic brought unprecedented challenges to the cruise industry, with passenger ships often labelled ‘hotspots’ for super-spreading events,” corresponding author and Prashant Kumar, PhD, MTech, founding director of the University of Surrey’s Global Centre for Clean Air Research (GCARE), said in a university news release.
“While significant progress has been made with indoor air quality management across the sector, there remains a clear need for targeted ventilation strategies in high-occupancy areas and energy optimisation in over-ventilated spaces,” he added.
A roadmap for cruise operators
In general, IAQ was good (less than 1,000 parts per million [ppm]), with CO2 ranging from 400 to 1,200 ppm. The estimated air change and ventilation rates implied that most ship areas were sufficiently ventilated. Using CO2 levels as a proxy for exhaled breath, the researchers estimated that the likelihood of airborne-disease transmission under normal speaking conditions was under 3%, mainly due to sufficient ventilation relative to occupancy in most areas.
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