The air quality of Delhi-NCR is continuously deteriorating due to stubble burning by farmers in many areas of Punjab, Haryana and Uttar Pradesh. After two days of relief, the Air Quality Index (AQI) in Delhi-NCR areas has crossed 400. According to data released by the Delhi Pollution Control Committee, the air quality index was recorded 401 in Anand Vihar, 405 in Alipur and 410 in Wazipur. Dense layer of smog has engulfed these areas in Delhi. Stubble burning takes place from September to December every year in neighboring cities of Delhi.