The capital sat under a dense layer of smoke late on July 5 as farmers on the outskirts of the Hanoi burnt rice straw.
People travelling along Nguyen Trai, Truong Chinh, Nguyen Chi Thanh and Giai Phong were particularly affected by the smog and poor visibility.
The smoke drifted over the city from 6.30pm, worsening as the evening went on.
Nguyen Quoc Hung, based in My Dinh, Hanoi, said, the smoke became worse at night, affecting visibility as he drove his motorbike.
Farmers are busy with their rice harvest and often burn the remaining straw, producing columns of smoke that drift across national highways 1A, 6 and 32.
Hundreds of piles of straw left smoke billowing for hours over the city.
Some farmers used the road verges to dry paddy and straw, further hindering traffic.
Straw smoke pollutes the air and can affect the health of children, the old and those who suffer from respiratory diseases. The smoke contains toxic and carcinogenic Polychlorinated Dibenzo-p-dioxins and Dibenzofurans.
No action has been taken to dissuade farmers from this anti-social practice.
Thang Long Highway covered with smoke
Nguyen Trai Street in the same situation
Smoke on Lang Ha Street
Column of smoke on National Highway 1A
Travelling through smoke
A national highway section used for drying paddy and straw