This Technical Report gives explanation on the pressure definitions and pressure units used by the gas network operators with regard to the standards of CEN/TC 234 “Gas infrastructure” listed in Clause 2. The European Standards of CEN/TC 234 comprise the functional requirements in the field of gas infrastructure from the input of gas into the on-shore transmission network up to the inlet connection of gas appliances, including transmission, distribution, storage, compression, pressure regulation and metering, installation, injection of (renewable) gases such as biomethane, hydrogen, gas quality issues and others.