The plasma focus is a source of pulsed radiation, which is of interest in various fields of physics and technology. Applications include soft X-ray microscopy, soft X-ray and electron beam lithography. The plasma focus is also a highly efficient source of fast neutrons. If one applies gas puffing instead of static filling, decoupling of plasma conditions in the breakdown and compression phases can be achieved. Results of experiments with a fast valve and accompanying 2D modelling of the dynamic gas target are presented. Among other advantages of gas puffing, neutron yield could be increased up to a factor of three in appropriate experiments. The concept of gas puffing has been extensively investigated in many Z-pinch experiments including multiple gas puffs. It seems desirable to increase the efforts to understand and optimise the gas puffing option for small and large plasma focus devices.