The office of the government’s Principal Scientific Advisor on Tuesday issued a detailed manual to prepare homemade masks using easily available items like old vests, t-shirts and handkerchiefs, stressing they are “70 per cent effective” in curbing the spread of coronavirus.

Masks lower the chances of coronavirus entering the respiratory system through droplets left in the air from an infected person.

Wearing masks is especially recommended for people living in densely populated areas, the manual states.

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Reducing the chances of inhaling the virus by wearing a protective mask cleaned thoroughly using a combination of approaches that use heat, ultraviolet light, water, soap and alcohol, will be vital to stopping its spread, the manual states.

“A double layer of 100 per cent cotton cloth is about 70 per cent as effective as a surgical mask at capturing small particles (up to five times smaller than coronavirus). This material is breathable and it is easy to find around the house. These masks can be easily reused,” the manual states.

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Before making the masks, the fabric should be washed well and boiled for 5 minutes. Adding salt to this water is recommended, as per the manual.

It states that homemade reusable masks only reduce the chances of inhaling droplets still in the air from an infected person.

“They do not give full protection. Homemade reusable masks must be washed and heated each day, as instructed. Reuse without washing should not be done,” it adds.

The manual is meant to provide a simple outline of best practices to make, use and reuse masks to enable NGOs and individuals to self-create such masks and accelerate widespread adoption of masks across India, a statement said.

The key criteria for proposed designs are: ease of access to materials, ease of making them at home, and ease of use and reuse.

“Analyses show that if 50 per cent of the population were to wear masks, only 50 per cent of the population would be infected by the virus. Once 80 per cent of the population wears a mask, the outbreak can be stopped immediately,” it states.