Trace Moisture determination in medical gases is very important. As a medical product they must be produced and used accordingly. Production is therefore carried out under expert supervision. European and Inter-national standards are established for the regulation and determination of trace moisture in medical gases and equipment. Our measurement system for the determination of trace moisture operates according to the coulometric method using a phosphorus pentoxide measuring cell and meets the requirements of the German Institute for Standards DIN 50450 1:1987 08.