Researchers from the University of Nicosia have published their recent research, in relation to ventilation cabins of cruise ships, in the popular journal Physics of Fluids of the American Institute of Physics. The research examines how viruses spread in cubicles and other small spaces, and suggests ways to mitigate their spread.
The team consists of KProfessor Dimitris Drikakis, Dr. Ioannis Kokkinakis and Dr. Konstantino Reto. The researchers looked at how ventilation might affect the transmission of airborne viruses in a typical cruise ship cabin, based on guidelines developed before and after the pandemic.
About the research
During the period when the COVID-19 virus appeared worldwide, its impact was particularly negative in the cruise ship industry. Compared to other groups of people, passengers on these ships faced a disproportionate rate of infection, often finding themselves paradoxically confined to the ship for quarantine purposes. Consequently, there has been an imperative to focus on strengthening the ventilation systems on cruise ships, as the effective distribution of fresh air within the cabins and enclosed spaces is an important measure to limit the transmission of viruses.
“The latest standards and regulations for room safety in relation to airborne transmission of viruses focus on high air exchange rates,” says Professor Dimitris Drikakis in a related press release issued by Physics of Fluids< /em>. “However, this solution can be inefficient in terms of energy consumption, and can hinder passenger comfort as it requires strong air currents. Also – and this is particularly important – it can disperse saliva droplets up to five times more when passengers happen to cough.”
The research team performed simulations of the virus droplets transferred when someone coughs in a typical cabin that accommodates two or more people, using different ventilation rates and positions of the person making the cough. Computational fluid dynamics tests ranged from 1.5 to 15 air changes per hour (ACH) to capture all possible scenarios, from minimal ventilation to rates exceeding the latest recommendations.
“The study shows that a higher ventilation rate is not the best strategy to avoid the spread of airborne diseases,” Professor Drikakis notes in the journal Physics of Fluids. “Complete evaporation of saliva droplets may not necessarily mean that all viruses or bacteria are immediately inactivated. Therefore, we should aim for minimal dispersion of droplets within the cabin and different ventilation strategies for occupied cabins.”
In studying the findings, the team concluded that optimal use of ventilation systems involves maintaining medium flow rates, i.e., about 3 air changes per hour (ACH), as long as a cabin is occupied. This should then rise to 15 ACH for at least 12 minutes after the cabin is cleared. This approach ensures complete air renewal for subsequent passengers. In addition, the group proposes that a similar minimum period of 12 minutes be observed as a “clearance waiting time” for rooms of comparable size equipped with a ventilation method up to at least 15 ACH.
“The main reason for the proposed rates is necessity to minimize the spread of droplets while maintaining good levels of ventilation, comfort and reasonable energy consumption,” said Professor Drikakis. “Keeping ventilation at the recommended values reduces energy consumption and improves passenger comfort compared to higher ventilation rates,” he explained.
Read more about the research here.
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