This document 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 . The European Standards of CEN/TC 234 cover the field of gas pipeline infrastructure for gaseous energy carriers and blends thereof from the input into the on-shore transmission network up to the inlet connection of gas appliances; This includes related functional requirements for injection, transmission, compression, pressure control, storage, blending, gas treatment, odorisation, distribution, measuring, and associated installation pipework, as well as related requirements such as safety, gas quality, sustainability, environment and emissions. Within the scope of CEN/TC 234, gaseous energy carriers and blends describe gases which are in the gaseous state when conveyed in the gas pipeline infrastructure such as hydrogen, hydrogen rich, and methane rich gases, dimethyl ether (DME) and propane and butanes used for combustion and/or as feedstock, excluding steam and compressed air.