This document provides guidance to relevant product standards, for compatibility assessment and qualification of materials for equipment used in commercial, industrial installations including gas burners, gas burning appliances and fuel gas infrastructures1 that are: fed by admixture of natural gas and hydrogen (blending) or pure hydrogen; operated at pressure greater than 10 bar (1 MPa) and up to 100 bar (10 MPa); operated within a temperature range of "20° C to +60 °C; NOTE 1 Temperature range outside of "20° to +60°C can be considered after risk assessment by the manufacturer, in compliance with relevant product standard and the requirements specified in this document. Except for critical equipment, where hydrogen requirements and material compatibility are defined by relevant specific, national and international product standard, according to CEN/TR 17924 and CEN/TR 17797, no specific requirements are necessary, as detailed in this document (see also Figure 1), under the following conditions: for a homogeneous mixture of natural gas and hydrogen with a hydrogen content not exceeding 10 % by volume, at operating pressures up to 100 bar (10 MPa); or for operating pressures up to 10 bar (1 MPa) with a hydrogen content up to 100 % by volume. Equipment is classified as critical when it s subjected to fatigue or specific mechanical stress due to specific operating conditions and applications (i.e. compression and pumping station, specific industrial installations, fuel tanks for vehicles, & ). This document represents minimum requirements and does not restrict the use of better procedures or materials. The following items are detailed in this document: metallic materials; non-metallic materials; validation tests.