According to CPCB measures, an AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', 401 and 450 'severe' and above 450 'severe-plus'.

Delhi's air pollution woes continue to get worse with each day, as over 14 areas in the national capital recorded an AQI of over 400 on Sunday. Most of these areas that had ‘very poor’ air quality last week, have now fallen to the ‘severe’ zone, CPCB data showed.

In the latest development, the National Capital wakes up witnessing thick smog. The Air Quality Index(AQI) remains in the Severe category. #WATCH | Delhi: A layer of smog envelops the National Capital as the air quality continues to remain in the ‘Severe’ category as per the CPCB.

Every year, Delhi and northern states battle hazardous air during the winter months of October to January due to plummeting temperatures, smoke, dust, low wind speed, vehicular emissions and crop stubble burning. This time, experts say that the condition is likely to get worse in the coming days.

Northern India encountered the recurring annual pre-winter event of air emergency where the Air Quality Index (AQI) readings of main pollutant PM 2.5 breached the 400-mark of “very poor” and landed the air of Delhi, Punjab and other northern cities into the “hazardous” category.

After reaching a peak, Delhi’s AQI has remained in the ‘severe’ category for the fourth day in a row. Covered in a thick blanket of fog and pollution, the poor visibility has even caused many school to remain closed for the past few days.