Main Ventilation Shaft Section A 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 contains a swarm of Parasites that are most easily avoided using Morph Ball.
After the frigate crashed into the Tallon Overworld, a large portion of the room was flooded. In the unflooded portion, there is a swarm of Tallon Crabs. The flooded portion contains some Fish and a door leading to the Reactor Core.
- Cargo Freight Lift to Deck Gamma (leading on from Subventilation Shaft Section B) (Before crash) (via Ventilation cap)
- Main Ventilation Shaft Section B (via Blue Door)
- Reactor Core (After crash) (via Blue Door)
- The Crash-Ship-MAE theme plays in this room after the frigate crash.
- How this room and the other surviving Main Ventilation Shafts ended up connecting to the Reactor Core after the crash instead of the Cargo Freight Lift to Deck Gamma is unclear. The door to this room in the Cargo Freight Lift is still present, although the two rooms are no longer connected.