Abstarct: The aim of the current project was to numerically investigate the air conditioning system in a passenger train cabin to reduce the risk of the spread of the Covid-19 virus. In order to investigate the purpose of the project, the CFD method has been used, one of the methods of air conditioning to increase air safety and the removal of particles. The train is one of the environments with high population density, widely used and a place for the rapid transmission and spread of the Covid-19 virus. Different methods have been provided for air conditioning, and the air conditioning method is one of the suitable methods for air conditioning in the train. The train air conditioning system in underground stations is a mechanical system that has the necessary equipment for air conditioning. Controlling the interior environment in these vehicles is very important to provide thermal comfort and reduce the risk of airborne disease transmission. Air conditioning systems of public vehicles need continuous air renewal and maintain thermal comfort in high density spaces. In this research, modeling and ventilation methods were discussed in order to increase air safety and reduce the effect of the spread of the Covid-19 virus in the train. This research presents a computational and numerical study to investigate the fluid dynamics of particles infected with the Covid-19 virus in a passenger train cabin. To investigate the performance of the air conditioning system in a passenger train cabin, the emission of particles in a public space was evaluated. The design of the 3D model of the half cabin of the bus train along with the entrance and exits of ventilation inside the cabin with SolidWorks software, dimensions of the cabin, ventilation valves and seating distances of its passengers were considered according to the standard. Also, the assumption of the problem is that the passenger in the first row is sitting next to the window and he sneezes and coughs, and therefore the velocity inlet boundary condition was considered for the passenger's mouth. In the case of sneezing, saliva drops reach the back row of the person sneezing faster after hitting the cabin wall. But it does not reach the two rows behind, and the air outlet ventilation directs a smaller part of the droplets to the outside. In the case of coughing, the saliva droplets do not reach the back row of the coughing person after hitting the cabin wall, and due to the lower momentum of the coughing particles, the air outlet ventilation directs a large part of the droplets to the outside. The results show that the geometric shape and position of the air inlet and outlet doors have a significant effect on improving and reducing the risk of the spread of the Covid-19 virus and the contamination caused by the virus, as well as the drops of human saliva released from sneezing and Cough in air conditioning and thermal comfort systems cause more and more passengers.