From
Dismantling myths on the airborne transmission of severe acute respiratory syndrome coronavirus (SARS-CoV-2)
Tang et al, Journal of Hospital Infection, Jan 2021 pre print
Several laboratory studies have already
shown that surgical and home-made masks are somewhat (but incompletely)
effective in both limiting exhaled particles, and in protecting wearers
from inhaling particles from others. Surgical masks can contain, and
therefore reduce, the dissemination of viruses shed by an infected
wearer by up to 3-4-fold (i.e. ∼67-75%), and even 100% in the case of
seasonal coronaviruses.,
When an infectious person wears a mask or face covering, the size of
the exhaled plume is also reduced and this also helps to reduce the risk
of exposure to those nearby.
Surgical
masks also protect the wearer, by reducing the exposure to incoming
droplets and aerosols from infected individuals by an average of 6-fold
(range 1.1 to 55-fold)., The filtration capacity of surgical masks in the micron size range is often considerable, although it varies between brands.
We know that the filtration capacity of N95/FFP2 respirators is better
if they have been appropriately fit-tested, to avoid leakage of aerosols
around the side of the respirator into the breathing zone.
Even
home-made cloth masks (made from tea cloths or cotton t-shirts) can
reduce the exposure from incoming particles by up to 2-4-fold (i.e.
∼50-75%).
This mainly depends on how the mask is made, what materials it is made
from, the number of layers, and the characteristics of respiratory
secretions to which it is exposed. Based on the evidence supporting a
role for airborne transmission of COVID-19, the use of N95/FFP2/FFP3
respirators by frontline healthcare workers should be recommended. For
those that cannot tolerate wearing these masks for long periods, the
less restrictive surgical masks still offer some protection, but it
needs to be acknowledged that these won’t be quite so effective
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