In Stage II vapor recovery testing applications, a pressure regulator is used to reduce the very high pressures present in the nitrogen source bottle to the very low pressure required to conduct various Stage II tests. Because of the large difference in inlet and outlet pressures involved in the accuracy with which the outlet pressure must be controlled, a pressure regulator that steps down pressure in two stages is generally required.

Alternatively, two pressure regulators, one with a high inlet pressure and one with low inlet pressure, may be used in a series to accurately control the nitrogen pressure.

See PEI/RP300.