Axial flow reaction turbines are typically used for expanding hydrocarbon gases or fluorinated refrigerants where a high molecular weights results in a low enthalpy drop across the turbine. When air or steam is used, the head drop across a single turbine is usually too high; therefore, multi-stage turbines can be used to reduce the head across each stage. Additionally, the power and resulting flow rates should be high enough to result in specific speed values of 60 or higher. If specific speeds are low, then impulse turbines may be better suited for an application.