The present invention relates to an electrode assembly, electrode structures and an electrolyser using said assemblies/structures, and in particular provides an electrode assembly comprising an anode structure and a cathode structure, each of said anode structure and cathode structure comprising i) a flange which can interact with a flange on an another electrode structure to hold a separator in between the two, ii) an electrolysis compartment which contains an electrode, and which in use contains a liquid to be electrolysed, iii) an inlet for the liquid to be electrolysed and iv) an outlet header for evolved gas and spent liquid, wherein the outlet header on one of the anode structure and the cathode structure is an external outlet header and the outlet header on the other one of the anode structure and the cathode structure is an internal outlet header, as well as to electrolysers comprising a plurality of such electrode assemblies.
