Airflow inside the car can be a transmission risk Covid: study

New York, December 5 (IANS): Airflow patterns inside a car’s cabin offer some suggestions for potentially reducing the risk of Covid-19 transmission by sharing journeys with others, say the researchers, including one of Indian origin.

The study, published in the journal Science Advances, used computer models to simulate the flow of air inside a compact car with various combinations of open or closed windows.

Simulations showed that opening windows – the more windows, the better – created airflow patterns that dramatically reduced the concentration of airborne particles exchanged between a driver and a single passenger.

Researchers found that blowing up the car’s ventilation system didn’t circulate the air as well as some open windows.

“Driving around with the windows open and the air conditioning or heating is definitely the worst case scenario, according to our computer simulations,” said study author Asimanshu Das of Brown University in the United States.

“The best scenario we found was having all four windows open, but even having one or two open was much better than having all of them closed,” added Das.

The computer models used in the study simulated a car, loosely based on a Toyota Prius, with two people inside: a driver and a passenger sitting in the rear seat opposite the driver.

The researchers chose that seating arrangement because it maximizes the physical distance between the two people (although still less than the 6 feet recommended by the CDC).

The models simulated the flow of air around and inside a car moving at 50 miles per hour, as well as the movement and concentration of aerosols from both the driver and passenger.

Aerosols are tiny particles that can remain in the air for long periods of time. They are thought to be one way the SARS-CoV-2 virus is transmitted, particularly in enclosed spaces.

The study showed that different combinations of open windows created different air currents inside the car that could increase or decrease exposure to the remaining aerosols.

Due to the way air flows outside the car, the air pressure near the rear windows tends to be higher than the pressure on the front windows.

As a result, air tends to enter the car through the rear windows and out the front windows. With all the windows open, this trend creates two more or less independent flows on either side of the cab.

Since the occupants in the simulations were seated on opposite sides of the cabin, very few particles end up being transferred between the two.

The driver in this scenario is slightly more at risk than the passenger due to the average airflow in the cargo from rear to front, but both occupants experience significantly less particle transfer than in any other scenario.

The simulations showed that while this configuration is better than the absence of lowered windows, it carries a greater exposure risk than lowering the window in front of each occupant.

“This scheme helps reduce cross-contamination between driver and passenger,” the authors wrote.

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