Masks may reduce cough cloud volume, but don't completely stop COVID-19 from spreading
The findings showed that the first 5-8 seconds after coughing are responsible for suspending infectious droplets in the air and, thereby, spreading the disease.
In order to protect ourselves during this pandemic, we have been asked to take many basic precautions. Some of these precautions involve maintaining physical distance, wearing masks and sanitising or washing your hands. These measures are believed to help control the spread of the virus amongst people. However, according to the recent research published in the November issue of International Journal of Multiphase Flow, even if a person is wearing a mask, the infectious droplets can transmit across several meters and can also stay in the air for a long period of time.
Masks may not provide you complete protection from infectious COVID-19 droplets
So far, it was believed that whenever a person coughs, the large droplets drop immediately due to the gravity, while the small droplets travel farther, almost in a straight line and then evaporate quickly.
But according to a group of researchers from the US, France and Italy, these small virus-containing droplets have the ability to convert into aerosols, which can remain in the surrounding for much longer. Aerosols can also travel several meters (up to 8 metres), thus increasing the risk of infecting people at a larger distance.
The scientists found that an average-sized saliva droplet of diameter 10 micrometres takes around 15 minutes to fall to the ground. This increases the risk of infection transmission even when the distancing rules are followed.
This risk of transmission increases when the relative humidity is high or the area is poorly ventilated.
Masks may reduce the volume of infected cough clouds
It is an established fact that when a person with COVID-19 infection coughs, sneezes or sings, infectious droplets are released into the surrounding air. In recent research, published in the journal Physics of Fluids on 20th October 2020, it was found that the cough of a COVID-19 infected person can contaminate a larger volume of surrounding air than previously believed due to the jet-like flow created by the cough.
In this study, the scientists studied the action of cough with the help of jet theory and previous studies based on this topic.
The findings showed that the first 5-8 seconds after coughing are responsible for suspending infectious droplets in the air and, thereby, spreading the disease. It was found that after that time period, the cough cloud (the cloud of aerosols formed after a cough) starts dispersing.
When compared with a person wearing a surgical mask, the cough cloud was found to be 7 times larger in the person who did not wear a mask. The volume of the cough cloud in a non-mask wearer was found to be 23 times larger than seen in the person wearing an N95 mask.
It was also stated that adopting some simple habits such as coughing into the elbow or using a handkerchief while coughing or sneezing, along with wearing masks, could help reduce the volume of the cough cloud.
With this study, scientists concluded that wearing a mask may not provide complete protection but can reduce the risk of transmitting the infection to other persons present in the room to a significant level.
For more information, read our article on How useful are masks against COVID-19 and how to use them.
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