One way to accomplish a GC "shutdown" that conserves gases would be to create a new instrument method (IM) that specifies low temperatures and column flow.
Then append a 1 minute "Equilibrate" line to the sample sequence and associate it with the "shutdown" IM. It is likely that an instrument failure message will occur in the message center, because the setup process cannot be completed for the "shutdown" IM, but the objective of conserving gases will be acheived.
For example, you could use the following settings for a 6890 GC shutdown IM in Empower:
General Tab: All installed and active modules are enabled.Oven Tab: Oven Enable is ON. Set temp to room temp (say 30 C).Column Tab: Set up Constant Flow to a low value (say 0.1 ml/min) to maintain a minimal gas flow through the column as the oven cools.Inlet Tab: Temp is ON. Set temperature to room temperature (say 30 C).Detector Tab: Flame/Filament is OFF. Temp is ON. Set temperature to room temperature (say 30 C). Set all flows to zero