DONGLIU (China) • The steel plants and cement factories scattered across China's Shandong province have made it one of the most contaminated areas of the world's biggest polluter. But for one company, that just makes the business climate better.
ASL Masks says it turned out more than 100,000 face coverings last year and aims to more than double that in 2016 as China struggles to shake off the toxic smog produced by its heavy industries.
At ASL's Dongliu facility, shabby buildings bearing faded signs from the 1980s exhorting "scientific innovation" are just visible through the haze - pollution levels were six times international standards when Agence France- Presse visited.
Dozens of middle-aged women wearing bright blue hats and aprons worked in near silence, sliding air filters into holes in the plastic products before threading on straps and yellow buckles.
"Smog is bad for the lungs. We all wear masks around here," said packager Chen Aimei.
China is the world's top greenhouse gas emitter and last year, air quality in some 300 haze-hit Chinese cities failed to meet national standards.
Last week, air pollution was reported in 180 of 338 Chinese cities at prefecture level or above. Forty-two of them, including Beijing and Tianjin, were categorised as "heavily polluted", the Ministry of Environmental Protection announced on Saturday.
Beijing was among the hardest hit, with an average PM2.5 density of 315 micrograms per cubic metre, according to Xinhua news agency.
Levels of PM2.5, tiny particles which can embed deep within the lungs, are usually above the World Health Organisation's recommended maximum of 25 parts per million.Public anger is mounting over the issue, but a wave of companies see silver linings to the smog, including air purifier and pollution monitor manufacturers, as well as mask makers.
Even when many Chinese factory workers had downed tools for the Chinese New Year holiday in February, ASL CEO Zhang Wenchao kept his staff on until the last possible moment.
"December to April is our busiest period... because it's the peak for pollution," he said.
ASL started making industrial masks in the 1980s, but has since turned to the more lucrative anti-pollution equipment market.
Demand has grown as authorities started releasing more data on the problem, and state media estimate that the Chinese pollution mask market was worth nearly 4 billion yuan (S$843 million) last year.
"People's awareness of pollution protection is increasing all the time. People know that PM 2.5 is bad for them," Mr Zhang said.
Shandong, in eastern China, is the centre of the industry, with another production hub, Dadian, dubbed the "mask village" for producing the cheapest specimens.
It can be a murky business. Dadian was hit by a scandal last year when local media reported that second-hand fabric used to make the masks was piled up beside fresh manure, and slept in by stray dogs.