Diwali air quality: Delhi-NCR remains worst, Chennai worsens; Northern/Western India hotspots, with some cities like Chennai and Patna deteriorating. A thick blanket of smog engulfed large parts of north India on Monday, a day after Diwali celebrations, with air quality deteriorating sharply across Delhi,. Burari Crossing and Sonia Vihar recorded the highest AQI at 441 each, followed by Vivek Vihar at 437, Delhi Technological University at 434 and North Campus of Delhi.