Viral droplets are generated by coughing, sneezing, or talking. And it is believed that face masks protect healthy people from inhaling infectious droplets and reduce the spread of people who are already infected.
But the global shortage of personal protective equipment during the pandemic has prompted some health agencies, such as the Centers for Disease Control in the United States, to recommend the use of homemade cloth face covers as an alternative to surgical masks.
Various types of material have been suggested for these, but based on little or no evidence of how well they work.
Therefore, a team of Australian researchers compared the effectiveness of single or double-layer fabric face liners (175 g / m² cotton fabric, with a thread count of 170 / inch) with a 3-face surgical face mask. layers to reduce the spread of droplets.
Double or triple layer better
The researchers used a custom LED lighting system and a high-speed camera to film the dispersion of airborne droplets produced by a healthy person without respiratory infection, speaking, coughing, and sneezing while wearing each type of mask.
Video recording showed that the 3-layer surgical mask was most effective in reducing the dispersion of droplets in the air, although even a single layer of fabric on the face reduced the spread of droplets when speaking.
But double-layer coverage was better than a single layer to reduce the spread of droplets when coughing and sneezing, the recording showed.
This is just one case, plus several other factors contribute to the effectiveness of cloth face masks, the researchers note. These include the type of material used, design and fit, as well as the frequency of washing.
However, according to their observations, a homemade fabric mask with at least two layers is preferable to a single-layer mask, they say, adding: “The guidelines on homemade fabric masks should stipulate multiple layers.”
And they emphasize: “More evidence is needed to inform a safer cloth mask design, and countries must ensure the proper manufacture or purchase of surgical masks.”
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