Air pollution can be defined as the presence of a substance, energy, from different components in environmental air activities through various community activities, including in the field of transportation because 70% of air pollution comes from vehicles. In line with various human needs to move places and activities, transportation activities will also increase following the existing growth, this progress can be seen by the increasing number of existing vehicles and continues to grow from year to year, including in the Special Region of Yogyakarta (DIY). The increasing number of vehicles can lead to congestion, which has a negative impact in the form of air pollution. One of the most common pollutants produced by motorized vehicles is carbon monoxide (CO), carbon monoxide produced by motorized vehicles produces a negative nuisance to public health. Carbon monoxide is a toxic gas, which can interfere with hemoglobin (Hb) to deliver fresh oxygen to the body, when oxygen supplies are reduced it will cause shortness of breath and even death as the worst consequence. Based on the problems described, it becomes a reference in predicting the amount of carbon monoxide parameters in the air using Fuzzy Time Series Cheng which will be displayed in a web-based application. The study was conducted using 30 data obtained from the Environmental Service of the city of Yogyakarta, with the results of the accuracy test using the Mean Absolute Percentage Error (MAPE) getting an inaccuracy value of 6.10% which is included in the very good forecasting category