Useful information

How effective is a handmade cloth mask against the new coronavirus?

2020/12/01

Wearing a mask when going out is the norm now.
We are no longer in a situation where “we can’t find a mask in the store!” Various types of
masks are on sale. Is there any difference in efficiency depending on the type (material) of the
mask?

How much can you prevent spread with cloth masks compared to surgical masks?

How much does the amount of virus inhaled change when a cloth mask, surgical mask, or N95
mask is used compared to without a mask?
A research group led by Professor Yoshihiro Kawaoka at the Institute of Medical Science,
University of Tokyo, investigated this using real new coronavirus and mannequins.
In this study, the heads of two mannequins were placed 50 cm apart, facing each other, one as
if it were an “infected person”, and droplets and aerosols containing the new coronavirus were
applied at a rate similar to that of a human cough. They compared how much the other
mannequin inhales from the mouth with “no mask”, “cloth mask”, “surgical mask”, and “N95
mask”.
First, when the side that emits droplets (infected person side) does not wear a mask and the
side that inhales (non-infected person side) wears a mask, the “cloth mask” suppressed the
virus to 60% compared to “without a mask”. It was found that the amount of virus inhaled can be
suppressed to about 80%, to about 50% with the “surgical mask”, and to about 10 to 20% when
the “N95 mask” is fitted perfectly.
All masks have a certain effect, but after all, other than the N95 mask, the cloth mask seems to
be a little less effective in preventing the spread of viruses than the surgical mask.

What is the effect of preventing the virus from spreading?

Next, if the side that emits the virus (infected person) puts on a mask and the side that inhales
(non-infected person) does not put on either a “cloth mask” or a “surgical mask”, it turns out that
it can be suppressed to 20-40% in most cases. By the way, it is not expected that an infected
person will actually wear an N95 mask, but when the infected party was wearing an N95 mask,
it was suppressed to almost 0%.
You can see that the effect is greater when the exhaling side wears the mask than when only
the inhaling side wears the mask.

20 types of mask materials put to the test

Researchers at the University of Cambridge in the United Kingdom are examining the rate at
which ultrafine particles are caught in as many as 20 materials used in handmade masks, such
as denim fabrics, cotton for shirts, and nylon.
In this study, they examined various items such as windbreakers, denim, wool felt, thick cotton
fabrics, socks materials, quilted cotton, cotton for shirts, nylon fabrics, thick and thin T-shirts,
non-woven interlinings, etc. In addition to cloth, there are 20 other types including pack
materials for vacuum cleaners.
It was found that all materials catch ultrafine particles to some extent. In particular, it has been
found that using two or more layers of cloth is more effective than a single layer of cloth
(although it also has the disadvantage of inhibiting respiration).
The study concludes that “a face mask made of common layered cloth will help filter ultrafine
particles and provide some protection to the wearer when commercial face masks are not
available.”
The results of these studies show that even handmade cloth masks can prevent the virus from
being inhaled at a considerable rate if they are worn layered over each other. However, as
Professor Kawaoka and his colleagues have verified by keeping a distance of 50 cm, social
distance is important even with a mask on.
◎ Reference
The University of Tokyo “Protective effect of mask against air transmission of new coronavirus”
https://www.ims.u-tokyo.ac.jp/imsut/content/000003662.pdf
BMJ Open. 2020 Sep 22; 10 (9): e039424.
“Ability of fabric face mask materials to filter ultrafine particles at coughing velocity”
https://pubmed.ncbi.nlm.nih.gov/32963071/