When traveling with company in a car, intuition can guide us on where to position ourselves and what to do to reduce the risk of contagion of COVID-19, although many times those actions are not as good as we think.
To clear up any doubts, a recent study used computer simulations to track airflows inside a car with passengers, and provided some suggestions for reducing the risk of airborne illness.
The work, conducted by researchers at Brown University, showed that different combinations of open windows created different air currents inside the car that could increase or decrease exposure to the remaining aerosols – tiny particles that can remain in the air for extended periods. of time).
This technique loosely simulated a car based on a Toyota Prius, with two people inside, a driver and a passenger sitting in the back seat on the opposite side of the driver.
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This position was not random, the researchers chose it to achieve the greatest physical distance between them, although it does not reach the 6 feet recommended by the authorities.
The simulations showed that the best situation was when all the windows were opened, since air flow patterns were created that drastically reduced the concentration of particles exchanged between the driver and the passenger.
“The best scenario we found was having all four windows open, but even having one or two open was much better than having them all closed,” said Asimanshu Das, a graduate student at the Brown School of Engineering and a co-lead author of the research. Also, the ventilation system did not circulate the air as well as some open windows.
Das co-led the research with Varghese Mathai, a former postdoctoral researcher at Brown who is now an assistant professor of physics at the University of Massachusetts, Amherst. The study was published in Science Advances.
The aim of this work was simply to study how changes in the airflow inside a car can worsen or reduce the risk of transmission of pathogens.
However, the authors stressed that there is no way to eliminate the risk completely, and it is best to follow the advice of the US Centers for Disease Control and Prevention (CDC), such as postponing the trip and staying in home or wear the mask throughout the journey.
Opening the windows was shown to be beneficial in reducing the risk of contagion since it increases the number of air changes per hour, reducing the concentration of aerosols.
The researchers also noted that because of the way air flows around the outside of the car, the pressure near the rear windows tends to be higher than the front ones. For this reason, air tends to enter through the rear windows and exit through the front ones.
With all windows open, this trend creates two relatively independent flows on each side of the cab.
Since the occupants in the simulations were sitting on opposite sides of the cabin, very few particles end up being transferred between the two.
In that situation, the driver is the one at slightly higher risk, as the average airflow in the car is from back to front, although both occupants experience significantly less particle transfer compared to any other scenario.
The experts also found that opening the windows next to each occupant, contrary to intuition, carries a higher risk of exposure compared to lowering the window opposite each occupant. Although it is a minor risk compared to traveling with all the windows closed.
“When the windows opposite the occupants are open, you get a flow that enters the car behind the driver, goes through the cabin behind the passenger, and then out the front passenger-side window,” said Kenny Breuer, an engineering professor at Brown and lead author of the research.
According to the author, this pattern helps to reduce cross contamination between the driver and the passenger. Breuer also cautioned that this “is the first study that we are aware of that actually looked at the microclimate inside a car.”
Despite the revealing of their findings, the researchers noted that even if airflows are known and adjusted, this cannot substitute for occupant wearing a mask.
How to travel by car safely
To reduce the risk of contagion during a car trip, you can also take these safety measures into account:
- Make sure you have hand sanitizer and spray, and disinfectant and paper wipes.
- Try to travel with family members or people you live with, to prevent the risk of contagion with strangers.
- Bring an extra mask in case the one you normally wear is lost or damaged.
- If you go down to buy something, remember to wear gloves, and clean the steering wheel and the surfaces of the car that you touch the most.
- Have food and water to avoid stops in stores or restaurants.
- Take into account the COVID-19 situation of the place you will visit.