The local consumer pricing supervision bureau in Zhangjiagang in East China's Jiangsu Province issued a warning to a restaurant that charged each customer a fee for breathing purified air.

The bureau conducted an investigation after receiving complaints from citizens who said that the restaurant charged customers "purified air fees" without advising them of these fees in advance, the Xinhua News Agency reported on Sunday.

The restaurant bought an air purifier to improve the dining environment and charged every customer 1 yuan ($0.15) to recoup the cost of the machine.

An official from the pricing bureau was quoted by the Xinhua News Agency as saying that air is a natural resource and that it is the restaurant's obligation to offer a good environment for customers, adding that therefore it should not "sell purified air" to customers if they do not ask for it.

The restaurant owner's lack of knowledge of pricing regulations was the main reason for the collection of "purified air fees," said the official.

The bureau asked the restaurant to rectify its charging practices within seven days.

The news triggered public discussion on social media, as hazardous air pollution choking northern China has led more people to become concerned about air quality.

A Net user writing under the moniker xiongmaolaoxu said, "I am willing to pay if the restaurant does buy an air purifier to improve the indoor air quality, but the restaurant needs to notify customers in advance."

Others said that it is a shame that people must resort to paying for clean air to breathe.