Experts have concentrated their studies on the spread of covid-19 in agglomerations, in spaces open to the public such as restaurants, department stores, shopping centers, gyms and airports. As opposed, the car has received less attention despite its daily use.
One explanation is that a car does not transport a large number of people to cause a contagion of large proportions, although experts admit that there are risks similar to those generated by a small, enclosed space, and because aerosols, tiny airborne particles that can transmit the virus, can remain in their cabinets.
To establish the possibilities of contagion that can occur inside a car, a group of scientists from American universities carried out a study, for which they used computer simulations to determine how air flows in a vehicle and how the virus is transported through it.
The report was published in the journal Science Advances and was updated last June. The study concludes that opening certain windows can create drafts that would protect both passengers and drivers of infectious diseases such as covid-19.
“Even if you cover your face in some way, you still blow out tiny aerosols every time you breathe.”said Varghese Mathai, a physicist at the University of Massachusetts, Amherst campus. “And if it’s a closed cabin, then you keep expelling these tiny particles and naturally they will build up over time.”
Mathai and his colleagues at Brown University (Asimanshu Das, Jeffrey Bailey, and Kenneth Breuer) used what is known as fluid dynamics simulations computational.
This is a tool commonly used by aerodynamic engineers to know how gases, liquids and air move, in order to create cars with less resistance (aerodynamic coefficient), or in the case of airplanes, to design airplanes with better lift.
The team did the tests in a car at 80 km / h with two people, the driver in the front seat on the left and a passenger in the back seat on the right. This is the most common travel option in public service vehicles (taxis).
In the first conclusions they discovered that the way the air flows around the exterior of the moving car creates a barometric gradient (pressure variation) inside the vehicle, with the air pressure in the front slightly lower than that of the rear, which causes the air that circulates inside the cabin to flow from the rear of the car to the front.
Passenger car, photo: Sci Tech Daily
Later, and always with the air conditioning on, they simulated and modeled internal airflow and aerosol movement with different combinations of open or closed windows. In the latter case, which was to be expected, between 8 and 10 percent of the aerosols expelled by one of the occupants of the car reached the other person.
And when all the windows were fully open, the ventilation rates increased and the fresh air flow blew many of the airborne particles out of the car. Only 0.2 to 2 percent of the simulated aerosols traveled between the driver and passenger.
Up to this point, these results are consistent with public health guidelines that recommend keeping windows open to reduce the spread of the virus indoors. “When you have so much air change, the residence time, that is, the time that the aerosols remain in the cabin is very short”Explains Joseph Allen, an expert on ventilation at Harvard University’s TH Chan School of Public Health, in an article on this topic published by The New York Times.
The best solution
As it is not possible to keep all the windows open due to weather conditions and for safety in many cities, the researchers modeled other options.
Among these and the one that provided the best results, in the case of taxis, was that the driver and the passenger will each roll down their windowBut the simulations determined that the best strategy was to open the windows opposite each person.
This setting allows fresh outside air to flow through the left rear window and out the right front window, thereby creates a current or helps create a barrier between the driver and the passenger. “It’s like an air curtain, it pushes all the air that the passenger exhales and also creates a region of strong airflow between the driver and the passenger,” Mathai explained.
Scientists warn that changing the number of passengers in the car or driving speed could affect the results, indicating that Self-care measures are essential when using public transport vehicles, and more when studies have shown that the virus can subsist on a surface from a few hours to several days.
In addition, there is research not officially published yet that would indicate that a 20-minute trip in a car with someone who emits infectious particles of the covid-19 it can be much more risky than sharing a classroom, a room or a restaurant with that person for more than an hour.
What happens when there are more occupants? While the opposing windows strategy works well for two occupants, the average in public service, in the case of family cars keep the windows halfway. seems to offer the same benefit as fully opening them, while only lowering them a quarter is less effective.
These general findings, Mathai says, hold true for many four-door, five-passenger cars and trucks. Where possible, keep all windows open if a vehicle is going with all seats occupied, and each passenger must wear a mask.
How long does the virus survive?
According to the Coronavirus Colombia website, studies indicate that coronaviruses can subsist on a surface from a few hours to several days. Every day there is more evidence of smaller particles called aerosols that can remain suspended in the air longer and travel longer distances. These sprays can also contribute to the transmission of the virus.
So far, what is known is that surface transmission is less risky than person-to-person. However, you can get it by touching a surface or object that has the virus on it and then touching your mouth, nose, or eyes.
Some studies say that the virus can survive on different materials. For example, in wood, four days; plastics, 2 to 3 days; stainless steel, 2 to 3 days; crystal, up to 5 days.
These materials are found in cars, and although Barriers such as plastics used in taxis can be effective, there is no guarantee that the passenger compartment will be properly disinfected, so it is advisable to avoid contact with the surfaces.