[en] Automatic translation: This report contains the results of a parameter study on the composition of the test helium in ZEMAK II. The partial pressure changes of the helium impurities are measured by gas chromatography. Particularly problematic is the thermal decomposition of the methane during the flow through the sample chambers at temperatures above 950°C. In order to carry out material tests under flowing test helium, it is necessary to it is necessary to select a sufficiently large volume flow rate. The process engineering of the helium circuit in ZEMAK II allows each test stand to be supplied with approx. 100 litres per hour, so that the required tolerances of the PNP test helium up to T = 950°C.