In environmental scanning electron microscopy (ESEM) high pressure applications have become increasingly important. Using this method makes it possible to study wet or biological samples without time consuming sample preparation and potential artefacts from this preparation. Unfortunately, the applications were limited by poor image quality. At the FELMI-ZFE we identified and improved crucial elements so that the image qualities at high pressures of a FEI Quanta 600 (field emission gun) and a FEI Quanta 200 (thermionic gun) were considerably improved by optimizing the pressure limiting system and the secondary electron (SE) detection system.