BEIJING -- Heavy smog is forecast to hit Beijing from Wednesday to Friday as the air is stagnant, making it unfavorable for diffusing pollution such as fireworks smoke.

The municipal environment monitoring center monitored a firework spree on the eve of Spring Festival (China's Lunar New Year) on Sunday night drove up the PM2.5 reading to as high as 700 mg per cubic meters. Thanks to strong wind, the air became clear on Monday.

However, the air started to become static from Tuesday, making smog aggregated in a vast area in northern and eastern China regions from Wednesday, the center warned.

China has a tradition to usher in a lunar new year by setting off fireworks which is believed to drive away evil spirits and fuel up festive atmosphere. Beijing, a city that has a firework ban, only allows fireworks for the Lunar New Year celebrations, which last from Feb. 3 to 12 this year.

However, with a rising awareness of air protection, the capital city has witnessed a big fall of firework consumption. From Sunday to Monday morning, sanitation workers swept away 413 tonnes of firework clastic on the streets, down by 33.8 percent from the same period of last year.