By: Christopher Sirota, CPCU
Back in July 2020, we posted about the concerns of the aerosol transmission of SARS-CoV-2, the COVID-19 virus. The Centers for Disease Control and Prevention (CDC) now has a web page dedicated to the topic. Per the CDC, experts generally consider close contact "exposure to respiratory droplets carrying infectious virus" as the primary means of transmission of the virus; however, the CDC also explains that '[a]irborne transmission of SARS-CoV-2 can occur under special circumstances […such as within locations that have] [i]nadequate ventilation or air handling that allow[s] a build-up of suspended small respiratory droplets and particles."
The interior of a motor vehicle could be such a location of concern.
Now, the New York Times has reported about researchers at Brown University that used computer simulations to examine the airflow within a vehicle, and its potential effect on airborne particles.
The article explains the simulation as follows:
The team simulated a car loosely based on a Toyota Prius driving at 50 miles per hour, with two occupants: a driver in the front left seat and a single passenger in the back right, a seating arrangement that is common in taxis and ride shares and that maximizes social distancing. In their initial analysis, the researchers found that the way the air flows around the outside of the moving car creates a pressure gradient inside the car, with the air pressure in the front slightly lower than the air pressure in the back. As a result, air circulating inside the cabin tends to flow from the back of the car to the front.
Per the article, with all the windows closed and the air conditioner active, the simulation study showed that about 8 to 10 percent of an occupant's exhaled aerosols could reach the other occupant. As one might guess, the researchers found that when all the windows were opened, the air flushed the interior air out, decreasing the potential exchange of aerosols to a range of 2 to 0.2 percent.
Since during winter months in cold regions leaving all the windows open might be impractical, the researchers reportedly simulated various configurations of opened and closed windows, and reportedly determined that
a strategy [better than opening the nearest window] was to open the windows that are opposite each occupant. That configuration allows fresh air to flow in through the back left window and out through the front right window and helps create [an airflow] barrier between the driver and the passenger.
The researchers reportedly suggest the results can be extrapolated to certain other sized vehicles as well, and hoped that the results might help inform mitigation efforts by ride-sharing services.