How does the flow of respiratory droplets affect COVID-19 transmission ?

What is it about?

Face masks are an important safety measure against COVID-19. They protect the wearer from virus containing droplets in the air. The manner in which droplets flow can affect how far they travel. Hence, upcoming studies are focusing on how droplets flow through different masks. In this review, authors discuss the findings from these studies. Moreover, they discuss which masks that are better at preventing droplet spread. They note that mass, speed, and droplet-to-air density affect the flow of droplets. A mask's design and material are also important to control the flow. Masks that allow droplets to flow and leak from the openings are not suitable. Surgical and cotton masks are quite successful at controlling droplet flow. They offer more protection than loose fitting cloth masks. However, surgical masks are 3 times more effective than cotton masks. How well a mask captures small droplets (filtration efficiency) affects its performance. Masks which have microscopic pores to contain small droplets are ideal. However, they may not offer enough ventilation to the wearer. For example, N95 masks filter tiny droplets with 95% efficiency. They are effective at controlling the spread of cough droplets. Regrettably, their design causes nasal flow resistance and breathing discomfort. This means that masks with better design are needed to improve air flow.

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Photo by visuals on Unsplash

Photo by visuals on Unsplash

Why is it important?

New masks with high filtration efficiency and comfort are the need of the hour. Masks with inbuilt ventilation and cooling are in the making. They may sport features like rechargeable filters and breathing rate monitors. People are more likely to use masks if they are comfortable to use. The insights offered in this review can support the design of such masks. They also include useful numerical methods to calculate droplet flow measurements. KEY TAKEAWAY: Understanding the flow of droplets via face masks can help develop masks with high protection and comfort. This can control the spread of contagious respiratory diseases such as COVID-19.