When SARS ended in 2003, little did I imagine I'd be in dire need of face masks again. COVID-19 has brought back memories of SARS. At that time, I was 10, in my fourth grade at school. I stayed at home for days. My parents one day brought a bag of gauze masks.

"During SARS, we wore gauze masks. There was basically no shortage as they were washable and reusable. A gauze mask cost around 2 yuan (29 cents)," my mom recalled recently.

Today, gauze masks seem old-fashioned. Face masks can generally be divided into four categories now: gauze masks, non-woven masks or surgical masks, activated carbon masks, and anti-particulate masks. In 2003, the first two types dominated the market.

Thirteen years on, masks that protect users from PM2.5, or fine particulate matter in smog that can damage lungs, became essential in some Chinese cities as thick air reduced visibility to shockingly low levels. Demand for PM2.5 masks surged in Beijing.

"At that time, we sold dozens of those masks priced around 32 yuan daily. Sometimes, the masks sold out by afternoon, and we refilled the stocks next day," recalled Wang Hu, then a salesman at a 7-Eleven convenience store in Beijing's Chaoyang district.

I was among the early birds to visit the store for those masks. A PM2.5 mask was invaluable. I prized its possession and, to save on costs, avoided unnecessary outdoor activities.

Thanks to the government's sustained efforts at air pollution control, Beijing skies are azure more often than not now. Off went the masks, until late January, that is.

The novel coronavirus that causes COVID-19 sent the demand for masks surging again. During the initial phase of the outbreak, there were mask shortages, to be sure. Till early February, most pharmacies in Beijing hung "masks are out of stock" boards on their closed doors or shutters. Fortunately, the Wumart branch near my home still sold masks.

Everyday, each customer could buy one pack of Korean masks priced 17.9 yuan. Not cheap but a big relief, given the situation.

As demand grew, China's mask makers swung into action. According to Qichacha, a data provider based in Jiangsu province, nearly 3,000 new firms registered as mask makers and entered the business in the space of 60 days (Jan 1 to Feb 29).

It was a throwback of sorts to 2003 when SARS broke out and the number of mask producers surged by 75 percent year-on-year to 105. Similarly, between 2016 and 2017, registered mask firms rose rapidly due to PM2.5.

The number of new mask firms this year must be a record, said a report from Time Business School, a Nanjing, Jiangsu province-based online platform.

Zhang Weiwei, an online content editor with the Business Review magazine, noted that with people's rising healthcare awareness and surging environmental problems, face masks are transforming from a special protective product to a daily necessity.

As demand constantly rises, enterprises that own mask manufacturing business will continue to grow. However, when the epidemic is over, whether the market is able to digest the newly added capacity remains to be seen, he said.

Hopefully, the COVID-19 epidemic will end sooner or later, and life should be back to normal. While walking past a neighborhood drugstore last week, I noticed masks were available again. I said a silent thank-you to China's mask producers.