The Covid-19 crisis has forced activity freezes, Lockdowns and calls to shelter-in-place have closed schools and non -essential businesses. Minimal activities from industrial sites, factories and construction sectors have minimized the risks for toxins to escape, in turn improving air quality. People are forced to stay at home practicing social distancing and working remotely. It is all aimed at controlling the spread of Covid-19 and hopefully reducing the death toll. But all this change has also led to some unexpected consequences. One among them is pollution levels and the natural environment. Before the start of the Covid-19 pandemic, the air around us had been deemed very toxic to breathe in due to the number of greenhouse gases that had been emitted over the centuries. But after the coronavirus lockdown commenced, there were slight changes in the environment. In the above context, a study should be undertaken to analyze the air quality indicators during non-lockdown period and the lockdown period is inevitable and essential. In this regard, the researcher wants to analyze the air quality of Chennai City by comparing the air quality indicators values like P.M.2.5, NO2, SO2, CO for the year 2019 with 2020 (same period). Accordingly, the researcher has collected data information and analysed it with the help of regression analysis and trend lines. The results revealed that during the lockdown period, everything was shut down and it would decrease the values of the above said air quality indicators, especially the concentration of P.M.2.5 because it is the major factor contributing to air pollution. It was proved by many earlier studies and this study also proved the same. The data set revealed that nearly 80 percent of the air pollution was due to the concentration of P.M.2.5 and its concentration was lowered during the lockdown period. Hence, to avoid air pollution, authorities should be taken steps to reduce P.M.2.5 concentration. It is good for the environment, the health of the living organism and the sustainable development of the economy.