A general view shows the view from Jingshan park looking towards the north of the city on a polluted day in Beijing on Oct 15, 2018. (NICOLAS ASFOURI / AFP)

BEIJING — Beijing Municipal air pollution emergency response office on Tuesday issued a yellow alert for smog, reminding residents to take precautions against it. 

Under Beijing's current three-tier warning system, the yellow alert is the least severe, followed by orange and red

The air pollution will persist until Thursday. The central part of the Beijing-Tianjin-Hebei region is forecast to see moderate to severe air pollution during the period, said a source with the Beijing Municipal Bureau of Ecology and Environment.

READ MORE: Ministry forecasts heavy air pollution

The yellow alert is issued when the air quality index surpasses 200 or the average density of PM2.5 stays above 150 micrograms per cubic meter for two consecutive days.

Under Beijing's current three-tier warning system, the yellow alert is the least severe, followed by orange and red. 

ALSO READ: Beijing issues orange smog alert

The yellow alert and above will trigger a series of compulsory emergency responses including the suspension of outdoor construction operations to reduce dust, the restriction of heavy pollution vehicles or the suspension of production in smokestack industries.