Air quality monitoring systems in Hanoi have shown an alarming readings since the morning of November 6.
At 7 am, the air quality monitoring system of the Vietnam Environment Administration showed that the air quality index at 556 Nguyen Van Cu Street was at 210. The air quality monitoring system of the US Embassy in Vietnam also showed that the air quality index at 6 am was 262. The PAM air quality system which is installed at 60 locations in Hanoi reported indexes from 150 to 300.
The air quality index over 100 is considered bad and people with respiratory and heart diseases are advised to stay home. If the indexes are from 200 to 300 then everyone is affected and advised to stay indoors.
According to the experts, the pollution may be caused by thermal inversions in winter. Le Thanh Hai, General Secretary of the Vietnam Meteorological and Hydrological Association, said pollutants were trapped by a layer of warm air at 300 to 1,000 metres.
The smog often appears at night and morning and disappears in the afternoon. The experts previously warned that pollution in Vietnam would become more serious in the winter due to heat inversion.
Nguyen Thi Anh Thu, the representative of GreenID, said their data collected in the past three years proved that winter was more polluted than in summer. The most polluted days so far this year was in January when the air quality index was near 300.
The citizens are advised to monitor the situation closely and try to stay indoors when the pollution reaches alarming levels. When it is necessary to go out, they are advised to wear masks to deal with fine dust pollution.