The coronavirus can hitchhike on very tiny particles that we emit when we speak.
“Every time you’re talking, you’re emitting a little cloud of invisible microscopic particles that are too small for you to see but are plenty big to carry the virus,” said William Ristenpart, a UC Davis Professor of Chemical Engineering who studies how particles move around. “These expiratory aerosol particles are playing a huge role, a huge role in transmitting the disease.”
Ristenpart says the particles are just 1/100th the size of a single strand of hair and spread through the air in a manner similar to smoke.
But despite the microscopic size of these particles, simple cloth face masks can do a lot to filter out virus particles and droplets.
“The more layers that you wear, you’re providing more filtration, so you’re protecting yourself on the way in. You’re also providing more filtration on the way out.”
While masks do not filter out 100% of virus particles, they can significantly reduce the amount that enter the air, even when masks do not fit properly, such as when your mask causes your glasses to fog up – a sign that air is escaping through the top of the masks.
“Yes, some of it can leak around the side of the mask, go up in the room air and then you might eventually inhale it. But that’s a lower probability chance than if you just breath a lungful of air,” said Ristenpart.
And as experts have repeated since the beginning of the pandemic, your risk of contracting or spreading the virus is lower when you are outdoors because the virus is quickly diluted by outdoor air.
“Another reason for that is not just air flow but also if its daytime, UV helps deactivate the virus,” said Ristenpart.
Epidemiological studies suggest that the vast majority of transmission is occurring indoors.