Smoke from fireworks and stagnant air have allowed airborne particles to accumulate and linger in China's capital, which continued to experience moderate smog on Sunday.
Smog began to accumulate from Friday, which was the Lantern Festival, the last day of the Lunar New Year celebrations which traditionally features the setting off of fireworks.
The density of PM2.5 weakened to 118 micrograms per cubic meter on average on Sunday in Beijing's city proper, down from 188 micrograms per cubic meter on Saturday, as the smog moved southwards to affect Hebei, Shanxi and Henan provinces, according to the Institute of Atmospheric Physics with the Chinese Academy of Sciences.
Beijing is expected to have improved air quality on Monday and Tuesday due to the effect of cold air.
