On Jan. 13, local developer Wang Jun found that downloads for his app had suddenly skyrocketed, totaling 58,000 in a single day.
"Usually, it only gets between 1,000 and 2,000 daily downloads", he said on Thursday.
But the spike in popularity wasn't due to any promotion or new feature. Instead, the cause was Beijing's pollution, with the air quality in China's capital reaching beyond hazardous levels, and off the index.
Wang is one of the developers behind the "China Air Pollution Index" app. And recently his product has garnered a new level of interest thanks to one of the worst bouts of prolonged pollution Beijing has seen.
"When the pollution went beyond the air quality index, all the social networks in China and media began paying attention to the problem," he said. "This caused the downloads to increase 30 times."
For much of this past month, smog in the city has blotted out the sun, and authorities have urged residents to stay inside in order to avoid exposure to the polluted air. Coal burning to heat homes during the winter has been cited as one major reason behind the dramatic decline in air quality.
Benefiting from the prolonged pollution, however, have been air quality monitoring apps, which have seen soaring download rates in the past month. In the case of Wang, his app now sees about 10,000 daily downloads.
Wang is the co-founder of Fresh-Ideas Studio, a small startup that began in October 2011, which has three full-time employees. The startup originally chose to develop an air quality monitoring app simply for "practice", he said.
"At that time the air quality was also bad," he said. "But we didn't think the app would get such a big reception".
The team then expanded it to include over 120 cities in the nation, with air quality data pulled from the U.S. Embassy and pollution monitors of China's Ministry of Environmental Protection. In total, the app has reached over 1 million downloads, most of them for iOS. Earlier this month, the company released an Android version.
Longcat Labs, another developer behind an air quality monitoring app for Beijing and Shanghai, said it also noticed a spike in downloads since Jan. 11. Downloads have tripled to about 100 per day, the company said in an email.
In the future, Wang's startup plans to continue improving its app, and will consider monitoring the air using its own equipment if its team can find an inexpensive solution.
He added that he thought it was ironical that his app succeeds when Beijing's pollution worsens.
"It's really weird. We are thinking about leaving Beijing," he said. "Our product is good, but the environment around us is getting worse."