The air quality across the national capital witnessed some relief as Delhi recorded an overall Air Quality Index (AQI) of 307, in the ‘very poor’ category on Tuesday morning,00 AM by the Central Pollution Control Board (CPCB). Delhi's air quality showed some improvement on Tuesday morning, with the city recording an overall Air Quality Index (AQI) of 307, still in the 'very poor' category, according to Central Pollution Control Board (CPCB) data.