“The mask fit my face well and protected me from droplets,” Zhang said. “There was just one thing: it was too difficult to breathe through.”

When a nation of 1.4 billion people was suddenly alerted and in many cases ordered to wear masks not only in public indoor places but also in the open air, the huge demand quickly exhausted supply.

Mask production capacity in China was 22 million a day – insufficient for the country’s population. There were hopes that the supply of masks would pick up after late January’s Lunar New Year holiday, which was extended to help prevent further spread of infection, but things did not look promising after factories reopened. By early February, despite mask manufacturers making 10 per cent more than before Lunar New Year, masks remained a rare commodity.

Making DIY masks became the top trending topic on Chinese online shopping site Taobao for several days. Materials became much sought-after, from nose bars to the non-woven fabric used in disposable surgical masks to filter out viral droplets. An online shop based in Fujian, southeast China, said it had sold more than 5,500 packages of DIY mask materials that can make 50 to 200 surgical masks apiece.

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Zhang spent 200 yuan (US$29) on materials online, from which she made 60 surgical masks when they arrived last week. She is a qipao designer and has a sewing machine at home. The outer layer was a blue waterproof non-woven fabric, over a layer of melt-blown fabric that can filter out most germs and droplets. The inner layer was made with a face flannel.

“I sent some to my parents and relatives,” Zhang said. “I am not sure how protective they are, but the good thing is our city hasn’t had any new cases for a long time.”

DIY mask production is being taken very seriously, spawning online chat groups to discuss reliability of materials and disinfection methods as people try to make theirs as safe and professional as possible.

Alex Zhang, an office worker in Shanghai, donated her N95 masks to Wuhan, the epicentre of the coronavirus outbreak, when hospitals in the city appealed to the public for protective gear amid an acute shortage – but soon found herself short of masks herself.

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The Shanghai government allowed households to buy a certain number of surgical masks, but it was not enough for her family. Taking apart an N95 mask to see what it was made of, she felt assembling the layers of fabric required no special technique, and decided to do it herself.

Zhang spent 45 yuan on two square metres of melt-blown fabric to stop viruses, and sandwiched it with two layers of nonwoven fabric and an air pad. She sewed the layers together and put them in an electric oven at 70 degrees Celsius (158 Fahrenheit) for a minute, for disinfection. The finished mask is attached using a plastic band.

“Each mask cost about 3 yuan [43 US cents] and was almost like an N95 filter,” Zhang said. “I didn’t find it difficult. I am quite satisfied with my masks and feel very safe to wear them in crowded places.”

She later bought nursing pads, which are already disinfected, to replace the layer closest to the face.

DIY masks have also been used where large amounts of protective gear are needed. Garment manufacturer Shenzhou International, in the coastal Zhejiang province, assigned 100 staff to make masks with melt-blown non-woven fabric to meet the needs of its factory workforce of nearly 15,000, who needed two masks each per day, according to a report by Ningbo Daily.

Hospitals short of masks have mobilised nurses to make their own using a non-woven fabric used to wrap disinfected medical products. At least three hospitals, in Xian in central China and in Jinhua, Zhejiang, have tried making masks for medical staff not serving on the front line, according to media reports.

DIY handmade face masks in Hong Kong

However, facing a shortage that will not end any time soon, health authorities have changed from saying people should discard masks every four hours to advising recycling them when possible.

A guideline issued by the National Health Commission said healthy people could wear masks repeatedly and for a longer time.

“Masks for repeat use can be hung in clean, dry and airy places or put in a clean paper bag,” its guidelines said. “The masks must be placed separately to avoid contact with other masks.”

Making masks with layers of cotton bandage is acceptable, because they can stay dry when breathed on, but plastic wrap is not recommended, because it blocks the ability to breathe entirely, according to Cai Haodong, an infectious diseases specialist at Beijing’s Ditan Hospital.

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Cai said her hospital did not have surgical masks, nor N95s, during the severe acute respiratory syndrome (Sars) outbreak in 2003, and hospital staff made masks for use by front-line medics, disinfecting them with boiling water and drying them in the sun.

“The key is to keep the mask dry,” Cai said. “Self-made masks offer some degree of protection and it is better to wear them than nothing.”