The spurt has been caused by calm wind movement and increased humidity. The polluting particles, of microscopic sizes, are not getting dispersed due to the atmospheric phenomenon, an IMD official explained.
Although visibility averaged above a kilometer, it will start coming down once the temperature drops to single digit which will be followed by formation of fog and subsequently smog, he said.
The national air quality index of Central Pollution Committee Board (CPCB) had 'severe' readings of the Punjabi Bagh, Mandir Marg and R K Puram stations, where PM 2.5 was the most prominent pollutant.
System of Air Quality and Weather Forecasting And Research (SAFAR) stations in Delhi University, IGI Airport, Dhirpur also had 'severe' Air Quality Index (AQI), bordering 450 in most cases. The 24-hour average of PM 2.5 and PM 10 were 197 and 330 micrograms per cubic metre respectively.
Permissible levels of PM (particulate matter) 2.5 and PM 10 are 60 and 100 micrograms per cubic metre respectively and consistent exposure to anything beyond that can harm the respiratory system as the particles embed themselves deep inside the lungs.