You only need to open your car windows for 10 seconds to almost entirely stop the build up of coronavirus in the air, a study has found.
Scientists have admitted they were somewhat surprised that regularly opening car windows can cut Covid-19 particles by 97%.
The study, by Swansea University, found the difference in air pressure between the inside and outside of a moving vehicle created a through-draught to suck out the virus.
The effectiveness of this is dependent on the speed you’re travelling: for driving below 30mph, opening all four windows is most beneficial whereas on faster roads, opening two on a diagonal can have an even bigger impact.
The researchers, headed by Professor Chenfeng Li of Swansea University, have set out a step-by-step guide to reduce exposure to the coronavirus when travelling by car. The key findings are:
- all windows should be open for car travel below 30mph.
- however, once speed increases above this, it is more effective for only two opposite windows, one in the front and one in the back, to be opened occasionally to create a diagonal flow of air. For example, driver side window and rear passenger side window.
The research focused on the fact that airborne transmission of Covid-19 happens in two ways: via large liquid droplets coughed out, or through smaller aerosol spray emitted when breathing. While the large particles are heavy enough to fall on to a surface within a few seconds, the aerosol spray evaporates leaving the virus circulating in the air for up to an hour.
Professor Chenfeng Li in his lab at Swansea University
(Image: Swansea University)
Project lead Prof Chenfeng Li said it was this aerosol effect which could be significantly reduced by opening windows. He explained: “Based on our scenario, and unsurprisingly, optimal ventilation comes from having all four windows open for city driving (up to 30mph).
“However, perhaps surprisingly, the diagonal flow from the driver side window to the rear passenger side window is the most effective option for getting the virus out of the car when driving above 30mph. This is because a sustained and dominant air flow from the front to the rear is formed when two diagonally opposite windows are open and the other two are closed.
“At higher driving speed, this strong diagonal air flow is more effective to discharge the virus particles out of the car than the turbulent air flow formed by opening all four windows.”
So effective is this process, it’s only necessary to do it for 10 seconds at a time, every five to 10 minutes, or whenever somebody coughs or sneezes, Professor Li added.
He said: “We can also conclude that sitting at the front is a lot safer than sitting at the back, because of the increased contamination within the rear part of the car due to the fact that the in-car air flow predominantly moves from the front to the rear, trapping some of the virus particles in the rear zone.”
As part of the research, the use of face masks was also studied. The results showed that wearing a face covering reduces the emission of the virus by 90% and that the intake of the virus by passengers was reduced by 70%.
Read more:We went to shops in Cardiff to see how many people are still wearing masks
Professor Li sits on the Welsh Government coronavirus Technical Advisory Group. His findings supported recent guidelines for taxis and private hire vehicles.
In Wales, masks are still legally required on public transport and in all public indoor areas apart from pubs and restaurants.
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