New Delhi, Jan. 22 -- A thick blanket of smog covered the national capital on Thursday, forcing residents to breathe foul air whether they stepped outside or stayed indoors without air purifiers.

At 8 am, Delhi's Air Quality Index (AQI) stood at 312, at the lower end of the 'very poor' category, according to data from the Central Pollution Control Board (CPCB) available on the SAMEER app. The reading was marginally better than Wednesday's average AQI of 330.

Experts attributed the slight improvement in air quality to stronger winds over the city. Westerly winds, with speeds of up to 15 kmph, prevailed over Delhi in the past 24 hours, data from the India Meteorological Department (IMD) showed.

Wind speeds are likely to increase to 30-40 k...