How effective is your face mask?

New Delhi, May 29 (DN&V): Studies show that a mask can reduce transmission of SARS-Cov-2, the virus that causes Covid-19, by up to 99%. And it doesn’t matter whether your mask is branded or home-made — both significantly cut the risk of transmission of infectious particles, depending on the material used.

The study also found that while even a single cloth layer can block droplets and aerosols, adding layers increases their efficiency to block the virus’ transmission — which is why 3-ply masks are usually recommended as protection against Covid-19 transmission. Even though the study concedes that a single layered cotton cloth may not stop isolated virions — the virus particle — considering that “most virus transmission occurs via larger particles in secretions, whether aerosol (<5 m) or droplets (>5 m), which are generated directly by speaking, eating, coughing, and sneezing”, it has a filtration efficiency of between 43%-94%. Disposable medical masks, on the other hand, have a filtration efficiency of 98%-99% for aerosols and 90% for virions.
The study also cited a 1975 study comparing four medical masks with a 4-layered reusable mask made of muslin — the filtration efficiency, based on bacterial counts, was 96%-99% for the medical masks and 99% for the cloth mask, while for aerosols (of <3.3 m in size), it was 72%-89% and 89%, respectively. It also found that for influenza-like illness, "the attack rate in health care workers wearing cloth masks was 2.3%, compared with 0.7% in health care workers wearing medical masks and 0.2% for those wearing medical masks continuously".

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