Main Ventilation Shaft Section B is part of a network of ventilation shafts in the Frigate Orpheon in Metroid Prime that Samus travels through after the Parasite Queen battle in order to escape the frigate. This section opens out into a room with 2 Auto Defense Turrets at one point. During Samus's escape, the door remains powered down. She is required to destroy both Auto Defense Turrets in order for the door to re-energize.
The room remains relatively intact after Orpheon crashed into the Tallon Overworld. A large rock wall has broken through part of the shaft. Both Auto Defense Turrets are both still active and are in fact stronger than before, but no longer are linked to the door's energy systems. A Sap Sac is found connected to the rock wall. The door leading to the hallway leading to Main Ventilation Shaft Section A was de-energized, requiring Samus to shoot a Power Conduit above the door with the Wave Beam.
- Sap Sac
- "Species: Sap Sac
- Chemical reaction within sac produces mild explosion when agitated."
- Powerless door
- "This door has no power.
A nearby Power Conduit must be energized for it to open. A blast of electrical energy will energize the conduit. The conduit radiates some heat that is invisible in the normal spectrum."
- If a Sap Sac has been scanned into the Log Book previously, the Sap Sac that appears in this room after the crash is rescannable and it provides Samus with only a portion of the Log Book entry.
- The Crash-Ship-MAE theme plays in this room after the frigate crash.