Clean nitrogen gas at ambient temperature and up to 35 MPa pressure is manufactured by pumping liquid nitrogen from a laboratory Dewar through a heated coil of tubing. The system and its components are described, particularly the high pressure liquid nitrogen pump and its close clearance seal. Performance is discussed in terms of thermodynamic, physical and mechanical parameters. Good agreement between observations of performance and the results of a theoretical model enables the model to be used as a basis for modifying the system in order to satisfy individual needs. Leakage past the seal may be controlled by varying the down stroke period and cylinder wall thickness. The system reliably delivers 2 Nl s^-1 (normal litres per sec.) at 30 MPa within ten minutes of an ambient temperature start.