In many developing cities, economic growth has led to an increase in atmospheric pollutant emissions, resulting in serious consequences for the environment and human health [1]. Carbon monoxide (CO) emissions, which are released into the environment daily, significantly contribute to the increase in respiratory diseases. The transportation sector is the main source of CO emissions due to the incomplete combustion of gas, oil, gasoline, coal, and oils. In March 2020, the World Health Organization (WHO) declared a global pandemic due to the outbreak and spread of COVID-19. A month later, strict social distancing measures were implemented in Guanajuato, Mexico, and activities decreased in general. It is hypothesized that during the lockdown, CO concentration levels decreased in the state of Guanajuato. Therefore, the main objective of this study is to perform a statistical analysis of CO emission reports in different municipalities of the state of Guanajuato between 2020 and 2021 and compare the data with that of the two previous years. A data collection of CO emissions was carried out using the database of the Secretary of Environment and Territorial Ordering. The municipalities of Celaya, Irapuato, and Salamanca were selected for this study. Statistical computing software RStudio [2] was used to perform a first comparison analysis between each of the months for each year.