Blasting car heater with closed windows poses high risk for COVID spread, study finds
Cruising in a car with people you don’t live with offers an easy opportunity for the coronavirus to latch onto you if someone is sick, just like in other enclosed spaces such as apartments and restaurants.
That’s because respiratory droplets potentially carrying the virus, when coughed or sneezed out by a sick person, remain suspended in the air before settling down. Over time, these particles can build up and increase risk of infection if not flushed out of the car.
Now, new research suggests how to position your windows to provide the best protection from infection, although there’s no way to reduce the risk entirely, especially if traveling in ride shares such as Ubers and Lyfts.
If weather permits, cruise with all four windows down, with passengers sitting in the back seat opposite of the driver. This option allows fresh air to flow through the car that can help reduce transmission risks, while placing passengers as far away from each other as possible, the team at Brown University in Rhode Island found.
This also increases what physicists call “air changes per hour.”
Alternately, keeping all windows shut with running air conditioning or heat is the riskiest option during the pandemic. “Blasting the car’s ventilation system [doesn’t] circulate air nearly as well as a few open windows,” the researchers said in a news release.
The study was published Dec. 4 in the journal Science Advances.
“Driving around with the windows up and the air conditioning or heat on is definitely the worst scenario, according to our computer simulations,” study co-lead author Asimanshu Das, a graduate student in Brown’s School of Engineering, said in the release. “The best scenario we found was having all four windows open, but even having one or two open was far better than having them all closed.”
The researchers say playing with window settings is no substitute for wearing masks while inside a vehicle, however; especially if it’s snowing or raining and windows must remain closed.
But it doesn’t have to be all or nothing either, the team said.
During their computer simulations based on the modeling of a Toyota Prius driven at 50 mph, the researchers learned that opening the windows farthest or opposite from the driver and back-seat passenger offered some benefits, too.
Their findings run against what many might think is the best option — to open the window closest to you to allow fresh air in. But that’s actually not the case, although this option is better than no windows down at all.
“When the windows opposite the occupants are open, you get a flow that enters the car behind the driver, sweeps across the cabin behind the passenger and then goes out the passenger-side front window,” study senior author Kenny Breuer, a professor of engineering at Brown University, said in the release. “That pattern helps to reduce cross-contamination between the driver and passenger.”
That’s because of the way air flows over a car from the outside.
Air pressure tends to be higher at a car’s rear windows than at those in the front, the researchers said, therefore air usually enters a vehicle through the back and exits through the front.
So, when all windows are down, the driver faces a “slightly higher risk than the passenger” because air is flowing from the back to the front, “but both occupants experience a dramatically lower transfer of particles compared to any other scenario,” the team said.
The study did not test the risk of actually becoming infected with coronavirus in the car, and the researchers’ methods may not apply to other car types such as mini vans or trucks, but they note their suggestions could make driving with others during the pandemic a little bit safer.
This story was originally published December 9, 2020 at 12:47 PM with the headline "Blasting car heater with closed windows poses high risk for COVID spread, study finds."
