Delhi's air quality 'very poor', might worsen by Friday: authorities

Delhi's air quality was recorded in the 'very poor' category on Thursday, with some regions in the national capital expected to witness further deterioration in conditions by Friday, authorities said.

The overall air quality index (AQI) of the national capital stood at 349, which falls in the 'very poor' category, the Central Pollution Control Board (CPCB) data showed.

An AQI between 100 to 200 comes under the 'moderate' category, 201 and 300 is considered 'poor', 301 and 400 'very poor', while that between 401 and 500 is 'severe'.

The Centre-run System of Air Quality and Weather Forecasting (SAFAR) said the air quality is likely to deteriorate further by Friday.

"Some areas of Delhi, particularly the south-east and the north-west part of Delhi, are likely to slip into the 'severe' category, but the overall AQI for Delhi city will remain in the upper side of 'very poor'," the SAFAR said.

"The AQI is expected to recover by the weekend but will continue to remain in the 'very poor' range with a decline in magnitude. A moderate fog will prevail and help both gaseous and particulate pollutants to become stagnant near the surface," it said.

The overall PM2.5 level (fine particulate matter in the air with a diameter of less than 2.5 micrometre) was recorded at 240 and the PM10 level at 413, the SAFAR said.

Neighbouring Ghaziabad, Faridabad and Noida recorded 'very poor' air quality, it added.

According to the Indian Institute of Tropical Meteorology, the maximum ventilation index on Wednesday was 4,300 sqm/second.

A ventilation index lower than 6,000 sqm/second with an average wind speed of less than 10 kmph is unfavourable for dispersion of pollutants.