Jahnavi Sarma
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Written By: Jahnavi Sarma | Updated : June 19, 2020 4:09 PM IST
Even when a mask is worn, some droplets can travel a considerable distance, up to 1 metre, during periods of mild coughing.
The COVID-19 pandemic is here to stay for some time to come. With no cure or vaccination in sight, it is imperative that you take the proper precautions and say safe. Frequent washing of hands, social distancing and wearing a face mask is now mandatory. Now researchers say that if you cough repeatedly, your face mask may just become ineffective and allow virus ridden particles to escape and infect others.
Face masks slow the spread of viruses, including the novel coronavirus that causes COVID-19. But their filtering efficiency is adversely affected by repeated coughing, say researchers. According to a study at the University of Nicosia in Cyprus, masks decrease droplet accumulation during repeated cough cycles. However, it remains unclear whether large droplets or small ones are more infectious. The journal Physics of Fluids published this study.
For the purpose of the study, the research team used precise computer models to map out the expected flow patterns of small droplets released when a mask-wearing person coughs repeatedly. They used an extended model to consider the effect of face masks and multiple cycles of coughing. The model was created using complex mathematical equations for turbulence and other flow effects. A sequence of coughs was modelled by applying several cycles of forward-directed velocity pulses to the initial droplets. The researchers performed numerical simulations that account for droplet interactions with the porous filter in a surgical mask.
The results show masks can reduce airborne droplet transmission. However, the filtering efficiency of masks is adversely affected by repeated coughing, as might happen when an individual is ill. Though previous work from this research group showed droplets of saliva can travel 18 feet in five seconds when an unmasked person coughs, this new study shows that repeated coughs reduce efficiency, letting many more droplets through.
According to researchers, the results are alarming. Even when a mask is worn, some droplets can travel a considerable distance, up to 1 metre, during periods of mild coughing. But without a mask, droplets travel twice as far, so, wearing a mask will help. A mask also decreases the number of droplets that leak out the side of the mask but fails to eliminate it entirely. Researchers say that these calculations reveal an effect on the droplet size due to turbulent flow encountering the mask, escaping and entering the environment.
According to them, the droplet sizes change and fluctuate continuously during cough cycles as a result of several interactions with the mask and face. The use of a mask will not provide complete protection. Therefore, social distancing remains essential, they add.
(With inputs from IANS)
