This is how coronavirus could spread in a grocery store

A new model developed to study the behavior of aerosols in a “grocery store-like” environment by four Finnish research organisations shows that these small airborne particles emitted during coughing, sneezing and talking are transported in the air and can stay and spread in this environment for several minutes.

If you are still visiting your usual air-conditioned departmental store to buy groceries, switching to an open shop might be a good idea.

A new model developed to study the behaviour of aerosols in a “grocery store-like” environment by four Finnish research organisations shows that these small airborne particles emitted during coughing, sneezing and talking are transported in the air and can stay and spread in this environment for several minutes.

The experiment takes into account the centralized ventilation measures in such a store, which doesn’t completely stop the spread of the aerosols from one corner to another.

Scientists believe that such particles can carry pathogens such as viruses including the Covid-19. The researchers used the supercomputer provided by CSC, the Finnish IT Center for Science Ltd and simulated the 3D visualisation of the results.

The simulation models a scenario where a person coughs in an aisle between shelves, very similar to a common grocery store and finds that the aerosols still travel and stay in the air despite the ventilation. The researchers modelled the airborne movement of aerosol particles smaller than 20 micrometres which is slightly larger than the usual aerosols emitted during the dry cough. “Extremely small particles of this size do not sink on the floor, but instead, move along in the air currents or remain floating in the same place” a statement on these findings released by Aalto University reads.

Another study published in the Journal of American Medical Association by Lydia Bourouiba at the Massachusetts Institute of Technology (MIT) emphasized on the role of “multiphase turbulent gas (a puff) cloud that entrains ambient air and traps and carries within it clusters of droplets” when a person coughs and sneezes. The paper concludes that “given various combinations of an individual patient’s physiology and environmental conditions, such as humidity and temperature, the gas cloud can travel 23 to 27 feet (7-8 m)”.

Both the above experiments are largely based on the biophysics of droplets and use the behaviour of the known droplets which carry the lesser-known virus to analyze the possible limits of their reach.