In this paper, curve-fitting and an artificial neural network (ANN) model were developed to predict R-Event. Expected number of new infections that arise in any event occurring over a total time in any space is termed as R-Event. Real-time data for the office environment was gathered in the spring of 2022 in a naturally ventilated office room in Roorkee, India, under composite climatic conditions. To ascertain the merit of the proposed ANN and curve-fitting models, the performances of the ANN approach were compared against the curve fitting model regarding conventional statistical indicators, i.e., correlation coefficient, root mean square error, mean absolute error, Nash-Sutcliffe efficiency index, mean absolute percentage error, and a20-index. Eleven input parameters namely indoor temperature (T In ), indoor relative humidity (RH In ), area of opening (A O ), number of occupants (O), area per person (A P ), volume per person (V P ), CO 2 concentration (CO 2 ), air quality index (AQI), outer wind speed (W S ), outdoor temperature (T Out ), outdoor humidity (RH Out ) were used in this study to predict the R-Event value as an output. The primary goal of this research is to establish the link between CO 2 concentration and R-Event value; eventually providing a model for prediction purposes. In this case study, the correlation coefficient of the ANN model and curve-fitting model were 0.9992 and 0.9557, respectively. It shows the ANN model's higher accuracy than the curvefitting model in R-Event prediction. Results indicate the proposed ANN prediction performance (R=0.9992, RMSE=0.0018708, MAE=0.0006675, MAPE=0.8643816, NS=0.9984365, and a20-index=0.9984300) is reliable and highly accurate to predict the R-event for offices.