ISO 6358-1:2013 specifies a steady-state method for testing pneumatic fluid power components that use compressible fluids, i.e. gases, and that have internal flow paths that can be either fixed or variable in size, to determine their flow-rate characteristics. ISO 6358-1:2013 does not apply to components whose flow coefficient is unstable during use, i.e. components that exhibit remarkable hysteretic behaviour (because they can contain flexible parts that deform under the flow) or that have an internal feedback phenomenon (such as regulators). In addition, it does not apply to components that exchange energy with the fluid during flow-rate measurement, e.g. cylinders, accumulators, etc.ISO 6358-1:2013 specifies requirements for the test installation, the test procedure, and the presentation of results for the steady-state method.