A method of starting a plasma arc torch is provided that includes directing a pre-flow gas and a start shield gas through the plasma arc torch during generation and transfer of a plasma arc, and switching from the pre-flow gas to a plasma gas, and switching from the start shield gas to a primary shield gas after transfer of the plasma arc to a workpiece. A method of stopping a plasma arc torch is also provided that includes directing a plasma gas and a primary shield gas through the plasma arc torch during steady-state operation, and switching from the primary shield gas to a stop shield gas during ramp down of an operating current.