42 design for others of accessories for use with an electrolyser to build a complete hydrogen and/or oxygen production plant, namely, AC to DC rectifier systems, gas and water header pipes, electrolyte addition and overflow systems, nitrogen purge systems, DC bus bars, water seals, mist eliminators, gas holders, compressors, filters, purifiers for removing oxygen, water, nitrogen and other contaminants, hydrogen and oxygen storage systems, deuterium recovery systems, control valves and control valve operators, gauges and monitoring instruments, and control panels and motor control centres; preparation for others of reports and studies for scientific research purposes, relating to hydrogen technology