The air quality in the national Capital deteriorated on Friday with an overall air quality index (AQI) of 321 micrograms per cubic on the National Ambient Air Quality Index (NAAQI).

According to the System of Air Quality and Weather Forecasting And Research (SAFAR), aunit of Ministry of Earth Sciences (MoES), the air quality is tagged with very poor air quality status.

Meanwhile, according to SAFAR, the concentrations of PM 2.5 and PM 10 stood at 130 in the 'very poor' and 237 in the 'moderate' category respectively. According to the SAFAR bulletin, New Year celebrations on December 31 night may increase emissions and worsen the air quality but the net effect is likely to keep AQI within the very poor or higher end of very poor for the next three days.

"AQI today indicates very Poor air quality. Prevailing cold wave conditions in the northwest region of Delhi and winds blowing from the west/northwest direction affect weather in Delhi. However, minimum and maximum temperatures show a tendency to increase slightly for the next 3 days (December 31, January 1 and January 2). Consistently high wind speeds are likely for the next three days. Mixing layer height continues to be 1.0 - 1.5 km," SAFAR said in its bulletin.

While the air quality of Noida remains in the very poor category with AQI at 304 and air quality of Gurugram is in the poor category with AQI at 252. As per the Government agencies, 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', and 401 and 500 'severe'.