‘How air conditioning spreads coronavirus aerosols decoded’

Using advanced air-flow simulation tools on super computers, scientists have analysed an outbreak of the novel coronavirus at a restaurant in China, findings that reveal how ventilation and air conditioning influence airborne virus transmission risk.

The study, published in the journal Physics of Fluids, analysed the complex flows that occur when cold airflow from air conditioners interacts with the hot plume from a dining table, and the transport of virus-laden particles within such flows.

"Our simulation captures various physical factors, including turbulent air flow, thermal effect, aerosol transport in turbulence, limited filtration efficiency of air conditioners, as well as the complex geometry of the space, all of which play a role in airborne transmission," explained study co-author Jiarong Hong from the University of Minnesota in the US.

While several studies over the course of the COVID-19 pandemic have used computer simulations to assess the airborne transmission of the coronavirus, Hong and his colleagues said few have directly modelled the actual infection outbreaks reported via contact tracing.

According to the researchers, the current study is the first realistic case modelled and linked directly with the simulation.

"It was enabled by advanced computational tools used in our simulation, which can capture the complex flows and aerosol transport and other multiphysics factors involved in a realistic setting," Hong said.

The scientists said there is a "remarkable direct linkage" between regions of high aerosol exposure index within the restaurant and the reported infection patterns.

They said the findings provide a strong support to airborne transmission in this restaurant outbreak.

Based on the results, the researchers cautioned that there could be two other potential modes by which the virus spreads in restaurants that are largely overlooked -- transmission caused by aerosols rising from beneath a table, and transmission associated with limited filtration efficiency of air conditioners.

"Our work highlights the need for more preventive measures, such as shielding more properly underneath the table and improving the filtration efficiency of air conditioners," Hong said.

"More importantly, our research demonstrates the capability and value of high-fidelity computer simulation tools for airborne infection risk assessment and the development of effective preventive measures," he added.