Hanoi warns residents to limit outdoor activity as air quality plunges

In a notice signed on Dec. 1 by vice chairman of the municipal People’s Committee Nguyen Manh Quyen, city officials said Hanoi is ramping up its response to the prolonged smog.

Health authorities will issue guidance to help people recognize periods of bad air and reduce outdoor exposure, particularly in the early morning and at night. Hospitals in the inner districts have been told to prepare for a potential rise in respiratory cases during days of dense pollution.

Schools will now monitor daily AQI readings and adjust outdoor activities based on air-quality levels. When the index hits "poor," students should avoid outdoor exercise. If pollution spikes to more dangerous levels, schools may shift schedules to keep children safe.

Construction sites will face tighter dust-control rules, including mandatory shielding, vehicle washing, misting and real-time monitoring with cameras, sensors and AI. Several neighborhoods, parks and major roads will pilot mist-spray systems aimed at lowering fine-particle concentrations.

City environmental teams will increase nighttime street sweeping, vacuuming and water spraying to keep dust from spreading. High-emission factories are being encouraged to move dust-heavy operations to periods with better weather conditions.

Hanoi is also expanding its air-quality monitoring network. VN-AQI data is updated continuously on the city's system, while experts are using satellites, drones, traffic cameras and the iHanoi app to catch illegal trash burning and rice-straw burning.

Northern Vietnam has recently faced many days of temperature inversion, still air and fog, conditions that trap pollutants near the ground. According to the HanoiAir forecasting model, this is the city’s third pollution episode of the season, running from Nov. 28 to Dec. 5.

On Dec. 1, Hanoi’s average AQI reached 143 ("poor"), and PM2.5 levels rose to 77 µg/cu.m, five times the World Health Organization’s recommended limit.

AQI measures air quality on a scale from 0 to above 300. The higher the number, the greater the health risk: 101–150 affects sensitive groups; 151 and above harms public health; and readings over 200 are considered hazardous for everyone.