Hanoi recorded an Air Quality Index (AQI) of 267 between 7 am and 8 am, a level considered very unhealthy, according to air-monitoring application IQAir.
Domestic data from the Environment Agency under the Ministry of Agriculture and Environment showed deteriorating conditions across the city.
At 8 am, the monitoring station at the gate of Hanoi University of Science and Technology on Giai Phong Street reported an AQI of 133, classified as poor. At Nhan Chinh Park on Khuat Duy Tien Street, the AQI rose to 188, an unhealthy level, from 94 a day earlier.
Several locations recorded hazardous readings. Quang Khanh reported an AQI of 517, while a station in Ha Dong Ward registered 312. Another site in Ha Bang Commune, on the city’s outskirts, recorded 287.
Health experts advised residents to limit outdoor activities when AQI levels exceed 300, urging people to stay indoors with windows closed. Vulnerable groups were warned to avoid going outside entirely and ensure safe indoor conditions.