A hydraulic compressor arrangement includes hydraulic rams A and B with associated non-return valves (13 and 16). A hydraulic pump (7), typically electrically operated, provides a pressurised fluid source to operate rams A or B to allow the associated chambers to receive and compress the low pressure gas provided via valve (30). The rams A and B alternately compress and allow entry of the gas so as to produce a continuing source of compressed gas via pipe (1) to a gas storage tank (2) via quick release coupling (3). Two stage compression is also described.
