Stabilizing polyacrylonitrile precursor yarns

The invention relates to a method for stabilizing yarns made of polyacrylonitrile by way of chemical stabilizing reactions comprising the following steps: - presenting a polyacrylonitrile precursor organ, - providing an application device for treating the precursor yarn with high-frequency electromagnetic waves, comprising an applicator having an application chamber, means for generating the high-frequency electromagnetic waves, and means for feeding the same into the application chamber, - generating a field of the high-frequency electromagnetic waves in the application chamber, comprising regions having minimal electric field strength and regions having maximum electric field strength and adjusting the maximum electric field strength in the range of 3 to 150 kV/m, - continuously guiding the precursor organ through the application space and through the field of high-frequency electromagnetic waves, while - feeding a process gas through the application chamber at a flow speed of at least 0.1 m/s relative to the precursor yarn, wherein the temperature of the process gas is set within the range of 150 to 300 °C, so that said temperature lies above a critical minimum temperature and below a maximum temperature.