People cover their faces as as smog continues to cover the skyline of Delhi

From the archive record

Air quality in Delhi continued to be rated as “severe” by monitoring systems in most parts of the city. Ayanagar, Dhirpur and Delhi University stations recorded “very poor” on the air quality index (AQI), while the remaining showed “severe”, according to SAFAR monitoring. Air quality is classified as “very poor” if the AQI ranges from 301 to 400 and “severe” if it is between 400 and 500. Overall, the average AQI in the Capital was over 400. AQI is an index to depict how clean or polluted the air is in an area. There are six AQI categories, namely Good, Satisfactory, Moderate, Poor, Very Poor and Severe, based on the concentration of eight pollutants — PM10, PM2.5, NO2, SO2, CO, O3, NH3 and Pb. Based on the measured ambient concentrations of these pollutants, a sub-index is calculated for e