IN China it is not just face masks and air purifiers that are in high demand, "mist cannons," used to lessen dust, have also got a wide following.

　　Hebei Yuanda Vehicles Manufacturing Co. sold more than 100 mobile mist cannons in 2015.

　　"The cannon business has taken off. We began promoting our business in the first half of 2015, and sales began to climb in the latter half, when smog was severe," said Wu Chao, vice manager of the company.

　　Mist cannons are specialized machines usually used by coal, cement and other industries. They spray liquid into the air where it combines with dust and falls to the ground. Many local environment authorities have added the cannons to their smog prevention arsenal.

　　The cannons can distribute mist as far 200 meters away and 60 meters in the air.

　　Such cannons can be seen on the streets of many central and northern Chinese cities, including Lanzhou in Gansu Province, Taiyuan in Shanxi, and Changsha in Hunan. Cities in the provinces of Hebei and Shandong as well as Inner Mongolia are also using the machines.

　　Cannon sales at Jiujiu Mining Safety Co. in Hunan has also soared in the last year. Sales of dust-removing equipment have increased by 30 percent year on year, said manager Mr. Peng.

　　"Before last year, we would have to seek out clients and promote our products. Now, they're coming to us," she said.

　　"We plan to develop more efficient cannons," she said.

　　"There are over 2,000 construction sites in Zhengzhou, and dust is among the major contributors to air pollution. The cannons have proven useful," said an official with the Zhengzhou environment protection bureau.

　　However, mist cannons use a lot of water, and environment experts dispute its effectiveness in removing inhalable particles such as PM2.5.