Abstarct: The Tunnel Boring Machines (TBMs) have revolutionized the tunneling industry to make the underground space safer, healthier, and more economical. To create a healthy work environment for people and equipment, the quality and quantity of airflow in TBMs should be sufficient to dilute gases, remove dust, and controlling the temperature. The numerical study of airflow distribution has mainly been concentrated on underground mines and road tunnels. Ventilation during the construction of long tunnels, especially the ventilation of the TBMs has received less attention. The two specific objectives of this research are first to study the airflow pattern and decreased dead zones in the TBM, and secondly, analysis of pollution concentrations from diesel locomotive and decreased pollutant volume to solve safety and health problems. The effect of increasing airflow quantity in the blowing fan to the dead zone volume and people breathing zone was studied. Several relevant scenarios such as switching off the exhausting fan, setting up complete duct from backup system to the mainfrxame area and the simultaneous effect of switching off the exhausting fan and setting up complete duct have been studied to decrease the number of dead zones and pollutant area. Modeling result shows that simultaneous use shutting down the exhaust fan and setting up complete duct can optimized airflow distribution and decrease dead zone and pollutant volume. The experimental measurements were carried out on the Chamshir tunnel to validate the results of a 3D numerical model.