Delhi's air quality remained in the very poor category Wednesday, though authorities expressed hope that a slight improvement may be observed in the next few days due to increased wind speed.

The Central Pollution Control Board recorded an overall air quality index (AQI) of 332, which falls in the "very poor" category.

An AQI between 201 and 300 is considered poor, 301 and 400 very poor and 401 and 500 is severe.

Mundka recorded severe air quality while 24 areas reported very poor air quality. Eight areas recorded poor air quality, according to the CPCB.

The overall PM2.5 (fine particulate matter in the air with a diameter of less than 2.5 micrometre) level was recorded at 186 and the PM10 level at 360, it said.

In NCR, Ghaziabad recorded worst air quality in severe category at an AQI of 404. Faridabad and Noida recorded very poor air quality while Gurgaon recorded poor air quality.

The Centre-run System of Air Quality and Weather Forecasting (SAFAR) said the overall air quality over Delhi continues to remain in the very poor range.

"It may improve a few notches tomorrow (Thursday) but will remain in very poor category. Moderate surface wind speed is the only weather factor not allowing pollution to accumulate significantly and working positively to an extent. Rest of the weather conditions are unfavourable for the air quality," the SAFAR said.

According to the Indian Institute of Tropical Meteorology, the maximum ventilation index was likely around 5000 sqm/second on Tuesday.

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

A Central Pollution Control Board taskforce has identified 21 hotspots of high pollution levels in Delhi-NCR and directed the respective area municipal corporations to take "focussed actions".

The taskforce has also asked authorities to carry out inspection in Loni Bhopura, in Ghaziabad, from where repeated complaints of violations of norms associated with pollution-causing activities have been received, according to minutes of a meeting of the taskforce held in Delhi Tuesday.

The taskforce has identified 15 hotspots in Delhi. They are: Anand Vihar, Bawana, CRRI Mathura Road, DTU, Dr. Karni Singh Shooting Range, Dwarka-Sector 8, Jahangirpuri, Mundaka, NSIT Dwarka, Narela, Okhla Phase-2, R K Puram, Rohini, Shadipur, Wazirpur.

Many of the hotspots are already experiencing severe pollution levels.

In NCR areas outside Delhi, six hotspots have been identified. They are: Sector-16A in Faridabad, Vikas Sadan in Gurgaon, Vasundhara in Ghaziabad, Knowledge Park-III in Greater Noida, Sector-125 in Noida and RIICO Industrial Area-III in Bhiwadi.