Ghaziabad, Greater Noida and Noida recorded "poor" air quality. (File)
Delhi's air quality showed an "unusual" improvement on Sunday due to increased wind speed, favourable for dispersion of pollutants, and settled in the "poor" category, authorities said.
The overall air quality index (AQI) was recorded at 262, which falls in the "poor" category, according to the Centre-run System of Air Quality and Weather Forecasting (SAFAR).
Six areas in the national capital recorded "very poor" quality air while 21 areas recorded "poor" air quality, according Central Pollution Control Board (CPCB) data.
The PM2.5 level (particles in the air with a diameter of less than 2.5 micrometres) was recorded at 124 and the PM10 level was recorded at 250, it said.
Ghaziabad, Greater Noida and Noida recorded "poor" air quality while Faridabad recorded "moderate" air quality, the CPCB data said.
An AQI between 0 and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe".
According to the SAFAR, the improvement in air quality is "unusual" for this time of the year.
"The major role is being played by late night faster wind speed which otherwise remains calm. However, the air quality is expected to keep oscillating between 'poor' and 'very poor' for the next three days," the SAFAR said.
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