TIANJIN, Nov. 30 (Xinhua) -- Northern China's Tianjin Municipality issued a yellow alert for heavy air pollution Friday, forecasting the pollution to persist until Monday.
The yellow alert is issued when the air quality index will surpass 200 for two consecutive days.
A series of emergency response measures were taken starting from Friday noon, including limiting emissions from enterprises and suspending construction work, according to local authorities.
Children, elderly and the infirm are advised to stay indoors.
Under China's four-tier warning system, red is the most severe, followed by orange, yellow and blue.