The effectiveness of a mask depends also on the type of material used, the design, the fit, as well as the frequency of washing, observes a study.
The masks in a cloth “home made” probably need a minimum of two layers, three preferably, to prevent the spread of the Covid-19 by droplets of the virus from the nose and mouth, according to a study published Friday in the monthly scientific Chest.
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“The global shortage of personal protective equipment during the pandemic, has led some health agencies such as the Centers for Disease Control (CDC) in the United States, to recommend the use of liners, facial tissue home-made, as an alternative to surgical masks. Several types of equipment have been suggested for these, but on the basis of “little or no evidence of their effectiveness”, the study said.
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in practical terms, a team of australian researchers has compared the efficacy of the coatings to the facial tissue single and double layer (cotton fabric 175 g/m2) with a surgical mask in three layers. Scientists have used a LED lighting system and a highspeed camera to film the dispersion of liquid droplets suspended in air produced by a healthy person without respiratory infection, during speaking, coughing and sneezing, with each of the two types of mask.
The video recording showed that the surgical mask, three layers was more effective in reducing the dispersion of droplets, even if a fabric covering to a single layer, reduce the spread of droplets when speaking. In the same sense, the coating on double-layer is shown to be more effective than a single layer.
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“Covid-19”, the new coronavirus
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This is only one case among several other factors contributing to the efficiency of gauze masks in public, note the researchers. It is also necessary to take into account the type of material used, the design and the fit, as well as the frequency of washing. However, on the basis of their observations, a fabric mask home made with at least two layers is preferable to a mask to a single layer, illustrate, suggesting that the “directives on the masks in fabric and home-made should provide several layers”. “It is necessary to have more evidence to inform the design of masks fabric safer, and countries should ensure that a manufacturing or purchase adequate surgical masks,” adds the study.
