Homemade coronavirus face masks should be two or three layers to stop spread of virus, study finds

A new study suggests that homemade face masks with two or three layers may be more effective in preventing the spread of the novel coronavirus compared with a single-layered face covering. 

Researchers in Australia performed a video study comparing the effectiveness of different layers of cloth masks to surgical masks in their ability to stop the transmission of droplets in the air when speaking, coughing and sneezing.

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The study, which was published in the journal Thorax., found the effectiveness varied in the cloth masks based on the number of the layers. The single-layer masks reduced spreading droplets from speaking, but the double-layer face covering was better at preventing the spread of droplets from coughing and sneezing, the authors stated. 

The Australian researchers used a LED lighting system and a high-speed camera to capture the scattered droplets in the air expelled by sneezing, coughing and speaking from a healthy individual wearing the different masks. The one-layer covering was made following the no-sew method, while the two-layer covering was made following guidelines from the Centers or Disease Control and Prevention (CDC).

"These visualizations show the value of using face masks and the difference between types of masks," the study's authors said. 

In addition to the number of layers, the type of material, the arrangement of different layers and the frequency of washing also affected the masks' efficacy, per the study. 

However, a surgical mask, the researchers found, "was the best among all the tested scenarios in preventing droplet spread from any respiratory emission." 

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"Based on the visualizations presented, in case of shortages of surgical masks, a cloth face covering with at least two layers is preferable to a single-layer one. Guidelines on homemade cloth masks should stipulate multiple layers (at least three)," the researchers stated. 

The study concluded that wearing a face mask overall is helpful in stopping the spread of the coronavirus.

"Even a single-layer face covering is better than no face covering," they wrote.