On December 7, their heavy smog shut off many cities in China, prompting Beijing to issue its first three-day pollution "red alert", according to Reuters.

But on December 10, it was lifted and was blown away by the high wind.

China’s pollution regularly garners world headlines. Breathing Beijing’s air, the Economist reports, could cause as much damage as smoking 40 cigarettes per day.

A restaurant in the Chinese city of Zhangjiagang has been caught charging customers a “clean-air fee” after it installed an air-filtering system in response to the blankets of thick smog that have shrouded the city in recent weeks.

The restaurant's owners recently purchased an air filtration system to improve the dining experience, and covered the cost by passing it on to customers without prior warning, the report says.

Diners at the eatery in Zhangjiagang city, Jiangsu Province, were charged one yuan ($0.15; 10p) each to cover the cost of purifying the air inside, the official Xinhua news agency reports.

Zhangjiagang municipality officials investigated complaints about the surcharge, and issued the restaurant with a warning, saying the air is a natural resource for human survival and not a commodity to sell.

On Weibo, the Chinese version of Twitter, a user wrote: “I am willing to give an extra yuan [for purifying the air].”

Another said: “They could have added the extra one yuan to the price of the dishes, but they didn’t ... there is nothing wrong with charging this extra fee. The kind of dining environment decides the kind of pricing.”

Ironically, restaurants were once of the biggest causes of air pollution in Beijing, especially roadside barbecues, leading to a crackdown by authorities in 2013.

Mostly Kitchen exhausts were the third-largest source of air pollution in the capital, leading to a ban on barbecues without purification systems.

New restaurants cannot open now unless they have exhaust filtration systems in place.