A nationwide lockdown was implemented in India for 29 days March 24^th to April 21^st of 2020 during the wake of the COVID-19 pandemic.The amount of pollution in cities across the country decreased dramatically in just a few days as a result of the imposed limits, prompting lockdown debates as a viable alternative to be implemented to combat pollution. This work finally emphasized a scientific look in the context of air quality throughout the lockdown time to the Indian metropolitan area of Kolkata. The air quality data of polluting parameters such as PM10, PM2.5, SO₂, NO₂, CO, O₃, and NH₃ for seven monitoring stations of the city of Kolkata has been used, namely Bullygaunge, Fort William, Victoria, Bidhannagr, Jadavpur, RabindraBharati, RabindraSarabor, spread across the metropolitan area of Kolkata, we used the “National Air Quality Index (NAQI)” to show pre-and during-lockdown air quality spatial patterns. The findings showed major changes in air quality throughout the lockdown period. The highest reduction in pollutants was observed in pollutants of PM10 (-60.82 percent), PM2.5 (-45.05 percent) and NO₂ (-62.27), followed by NH₃ (-32.12 percent) and SO₂ (-32.00 percent), CO (-47.46 percent), O₃ (15.10 percent) and O₃ (-32.12 percent). During the lockdown, the NAQI value was reduced from pre-lockdown to the end of the lockdown at-52.93 percent due to the lockdown effect in the study area. Overall, the study is focused on the planners and government agencies for suitable measures for controlling and attenuating the pollutant components of air quality.

Keywords: National Air Quality Index, COVID-19, Kolkata Metropolitan Area, Lockdown.