A new and promising technique for improving shock tube/tunnel performance is presented. This technique is able to produce higher reservoir enthalpy levels than the ones usually obtained with conventional shock tubes/tunnels, when operating in the Equilibrium Interface Condition. The new technique, which is tentatively being called "Gaseous Piston Technique", has been proven also to prevent combustion from taking place at the air-hydrogen interface, and seems to be capable to improve the available testing time by reducing the test gas contamination by the driver gas. The qualitative agreement of both numerical and experimental investigations is very encouraging.