Coronavirus in a cough: Tests show masks stopping the spread

  • An Indian study found that a surgical mask can considerably reduce a cloud of Covid-19 in a room 
  • In fact, anything that reduces the distance travelled by the cloud can reduce one's chances of infection
  • The study findings also led to a formula to keep the air fresh in enclosed spaces 


A cough could spread a cloud of Covid-19 throughout a room, but a face mask can greatly shrink the size and spread of that cloud, a new study finds.

In fact, the volume of the cloud without a mask is about seven times larger than with a surgical mask and 23 times larger than with an N95 mask, the researchers found.

"We found that anything that reduces the distance travelled by the cloud, such as a mask, handkerchief, or coughing into an elbow, should greatly reduce the region over which the droplets disperse upon coughing, and therefore the chances of infection," said researcher Rajneesh Bhardwaj, from the Indian Institute of Technology Bombay, in Mumbai.

Keep the air fresh

Using jet theory and data from the literature, Bhardwaj and colleague Amit Agrawal found the first five to eight seconds after coughing is critical for suspending droplets in the air and the spread of the disease. After that, the cough cloud starts to break up.

The study findings helped the researchers develop a formula to determine the maximum number of people that can be in a hospital ward, and the rate at which air in a room, elevator, movie theatre, car, plane cabin or restaurant needs to be circulated to keep the air fresh and reduce the odds of infection.

The report was published online on 20 October in the journal Physics of Fluids.

"We estimate this volume of the air, which may help to design ventilation of closed spaces and consequently reduce the spread of the disease," Agrawal said in a news release from the American Institute of Physics.

Image credit: Getty Images

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