Method for operating a fuel cell unit for a rail vehicle, comprising: - providing a compressed airflow, - providing a variable, and - supplying the compressed airflow through an air supply duct into a fuel cell component of the fuel cell unit and as a result cleaning the fuel cell component by means of the compressed airflow as a function of the variable, with which the provision of the variable comprises a detection of a measuring signal of at least one sensor, which is representative of an operationally relevant property of a process air in the fuel cell component of the fuel cell unit, and a determination of a value for the operationally relevant property of the process air in the fuel cell component as a function of the detected measuring signal and a comparison of the determined value with a predetermined threshold value for the operationally relevant property of the process air, and with which the supply of the compressed airflow through the air supply duct into the fuel cell component of the fuel cell unit and as a result cleaning of the fuel cell component by means of the compressed airflow is carried out as a function of the comparison of the determined value with the predetermined threshold value for the operationally relevant property of the process air, and with which the fuel cell component is embodied as a wetting unit for wetting the process air for the fuel cell unit, the operationally relevant property is embodied as an air humidity of the process air in the wetting unit and the at least one sensor is embodied as a humidity sensor for detecting the air humidity of the process air in the wetting unit, comprising: - detecting an air humidity of the process air for the fuel cell unit in the wetting unit, - comparing the detected air humidity with a predetermined threshold value for the air humidity of the process air in the wetting unit and - supplying the compressed airflow through the air supply duct into the wetting unit when the detected air humidity does not reach the predetermined threshold value for the air humidity. - providing a compressed airflow, - providing a variable, and - supplying the compressed airflow through an air supply duct into a fuel cell component of the fuel cell unit and as a result cleaning the fuel cell component by means of the compressed airflow as a function of the variable, with which the provision of the variable comprises a detection of a measuring signal of at least one sensor, which is representative of an operationally relevant property of a process air in the fuel cell component of the fuel cell unit, and a determination of a value for the operationally relevant property of the process air in the fuel cell component as a function of the detected measuring signal and a comparison of the determined value with a predetermined threshold value for the operationally relevant property of the process air, and with which the supply of the compressed airflow through the air supply duct into the fuel cell component of the fuel cell unit and as a result cleaning of the fuel cell component by means of the compressed airflow is carried out as a function of the comparison of the determined value with the predetermined threshold value for the operationally relevant property of the process air, and with which the fuel cell component is embodied as a wetting unit for wetting the process air for the fuel cell unit, the operationally relevant property is embodied as an air humidity of the process air in the wetting unit and the at least one sensor is embodied as a humidity sensor for detecting the air humidity of the process air in the wetting unit, comprising: - detecting an air humidity of the process air for the fuel cell unit in the wetting unit, - comparing the detected air humidity with a predetermined threshold value for the air humidity of the process air in the wetting unit and - supplying the compressed airflow through the air supply duct into the wetting unit when the detected air humidity does not reach the predetermined threshold value for the air humidity. - detecting an air humidity of the process air for the fuel cell unit in the wetting unit, - comparing the detected air humidity with a predetermined threshold value for the air humidity of the process air in the wetting unit and - supplying the compressed airflow through the air supply duct into the wetting unit when the detected air humidity does not reach the predetermined threshold value for the air humidity.