COVID-19 pandemic has shown a scary picture in a number of countries and as a preventive measure, entire India has been locked down for 21 days starting from 25-03-2020.

In Delhi, the lock down is from 22-03-2020 (the day of Janta Curfew) and there has been almost no movement of people and vehicles on roads in last 5 days. This has resulted in improved air quality in Delhi. In Delhi, prominent pollutants are PM10 and PM2.5. As per Central Control Room for Air Quality Management – Delhi NCR, the average values of PM10 and PM2.5 in Delhi NCR from 21-03-2020 to 26-03-2020 are as follows:

Date: 21-03-2020 (The day before Janta curfew):

Date: 22-03-2020 (The day of Janta curfew):

Date: 23-03-2020 (Starting day of Lock down):

Date: 24-03-2020 (Lock down continued):

Date: 25-03-2020 (Lock down continued):

Date: 26-03-2020 (Lock down continued):

These levels of PM10 and PM 2.5 indicate a significant declining trend in values of PM10 and PM2.5 due to restriction of movement of people and vehicles on roads as well as of stoppage of all other activities causing air pollution. During complete lock down, the air quality in Delhi-NCR is within the standards.

Further, the air quality index (AQI) of various Continuous Ambient Air Quality Monitoring Stations (CAAQMS), maintained by DPCC, CPCB and IMD in Delhi, on 26-03-2020 at 3:00 PM is in the range of 51 to 137 which is in the satisfactory/ moderate range.

There are six AQI categories, namely Good, Satisfactory, Moderate, Poor, Very Poor, and Severe. Each of these categories is decided based on ambient concentration values of air pollutants and their likely health impacts (known as health breakpoints). AQ sub-index and health breakpoints are evolved for eight pollutants (PM10, PM2.5, NO₂, SO₂, CO, O3, NH₃, and Pb) for which short-term (up to 24 hours) National Ambient Air Quality Standards are prescribed.

These results indicate that such measures can be taken to control severe condition (smog condition) of air pollution in Delhi NCR, which is happening every year in the month of November.