Energy barriers are useful because they allow solid matter through, but not gases, such as Oxygen and Neon. However, before matter passes through, the pressure on both sides must be equalized, to minimize the risk of explosive decompression.
Signal Units work through energy barriers, while COM units do not. Energy barriers are also present on Covenant Boarding Craft, on the end of the craft's penetration tip. They can also be garrisoned with infantry in Halo Wars' Skirmish mode.
Energy barriers are also used as exterior doors in hangar bays on Covenant starships. These include the shuttle bay doors on CCS-class Battlecruisers, as well as the hangar bays on Covenant corvettes. The barriers can also be configured to block all vehicles or personnel or allow them to pass through when required.
In Halo: Combat Evolved, it is possible to operate the shuttle bay doors. On the level Truth and Reconciliation, the player is able to access the doors by heading to the third floor of the Shuttle Bay and pressing X on the control panel. This is required to complete the mission, so you can escape in a Spirit with Keyes.
In Halo: Reach, on the Covenant corvette Ardent Prayer, the shields seemed to work differently: after Noble Six pressed a button, the shields still remained in place over the bay, but ships could now go in and out of them. Presumably they were simply lowered to a point things could travel through them while remaining in place to hold the atmosphere in the bay as the ship was in space.
- Halo: Combat Evolved (First appearance)
- Halo 2
- Halo 3
- Halo: Reach
- Halo 4
- Halo: First Strike
- Halo: Contact Harvest
- Halo Legends