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Because of this situation, more and more masks are made of cotton. The question is whether these masks are effective in preventing infections.

For more information, reporter Yoo Su-hwan.

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A mask with an electrostatic filter placed between two layers of cotton.

When it became difficult to get a mask, the women's association of Gangdong-gu, Seoul made it for the residents.

You can buy electrostatic filters online, etc. The cost of each filter is about 100 ~ 200 won.

The advantage of this mask is that it can be sucked back and made to fit your face.

The problem is performance, but in practice we have found it to work.

We measured the blocking effect by spraying particles in the form of drops of water on the mask and found that homemade cotton masks blocked 80 to 95 of the 100 particles.

This is similar to the KF80 mask approved by the Ministry of Food and Drug Safety.

The key is the filter.

If the cotton mask does not have an electrostatic filter, only about 20 out of 100 droplets can be blocked.

The preventive effect almost disappears.

[Lee Jung-mi / Head of the Pharmaceutical Analysis Team, Korea Institute for Health and Environment Research: The reason for using an electrostatic filter is that static electricity adsorbs fine dust particles. It must be attached with an electrostatic filter to be as effective as a KF health mask.]

However, experts advised that the filter should be cut and fitted to the size of the cotton mask to get the effect.

(Video coverage: Oh Young-chun, Yang Hyun-cheol, Video editing: Jeon Min-kyu)