Abstract: An electrolytic gas generating apparatus for producing a combustible mixture of hydrogen and oxygen by electrolysis of water is disclosed, for particular use in a gas welding apparatus. The generating apparatus comprises a d.c. power supply 100 connected to electrolytic cells 200, a dehumidifier 400 for scrubbing the gas mixture generated by the cells 200, a gas regulator 500, a modifier 600 which modifies the combustion characteristics of the gas and a flash arrester 660. Gas generation is controlled by a main control board 800 in accordance with sensors which measure parameters to calculate indirectly the gas flowrate and control this in accordance with demand.