Used to detect and monitor leakage of the inboard seal, these seal support systems can detect liquid leakage (API Plans 65 and 75) or gas leakage (API Plan 76), or a mixture of gas and liquid leakage (API Plan 75). A PD 76 (API Plan 76) system diverts non-condensing inner seal leakage from a dual unpressurized seal where the outer seal is dry running, to a flare or vapor recovery system.