Part I of this report covers considerations regarding test gases for assessing combustion related risks of supply with gaseous fuels of the second family (i.e. natural gases) blended with hydrogen of which the concentration may vary between 0 and a maximum hydrogen concentration X (called “X% H2NG” throughout this document) to gas appliances within the scope of the Regulation (EU) n°2016/426. If relevant, a specific view is given on 20% H2NG as this is often put forward as a meaningful limit if hydrogen injection is considered.
The document is mainly intended as input for CEN/TC238 – Test gases, test pressures, appliance categories and gas appliance types – in view of the revision of EN 437 for use of the above-mentioned gases.

Part II covers risks to be considered when revising existing gas appliance standards for H2NG supply.