In electrolysers, water is split into the components oxygen and hydrogen using electrical energy. Hydrogen is seen as a key element in the energy transition in order to temporarily store renewable electricity in order to decouple generation from consumption. One type that is particularly suitable for this application is the proton exchange membrane water electrolysis. The water that is split in the electrolysis process passes through porous transport layers to the cell membrane, where it is split into hydrogen and oxygen. The porous transport layers have the task of distributing the water over the entire membrane surface due to their internal resistance. They are also responsible for transporting the gases produced out of the cell and establishing electrical conductivity between the electrode and the membrane. The internal resistance of the porous transport materials results in a pressure loss, which will be analysed in more detail in this thesis. The aim is to better understand the pressure loss of stacks and cells and ultimately optimise the overall efficiency of proton exchange membrane electrolysis. To this end, the most common porous materials currently used in electrolysers are analysed in more detail and their pressure loss is measured when fluids flow through the media. A test block is being developed to describe the porous materials in terms of their pressure loss at different flow velocities. Based on the results, mathematical functions are set up to estimate the permeability, viscous and kinetic resistance of the different porous materials. By listing possible error influences at the beginning of the work, attention can be paid to their avoidance or minimisation when carrying out the tests. The main influences are the cutting of the samples and the sequence of the samples if several samples are installed on top of each other in the test rig. By taking possible error influences into account, it is possible to generate reproducible data. The investigations show, for example, that the number of samples has a significant influence on the pressure loss, as does the contact pressure on the samples, which is particularly pronounced for samples with higher elasticity. A trend line can be read from the recorded pressure loss points of the tested materials, which can be used to calculate the permeability, viscous and kinetic resistance.