Energy barriers, sometimes referred to as energy fields, are a type of visible energy field used to separate a pressurized environment from the vacuum of space. 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.
The Covenant use energy barriers as hangar doors, in airlocks and for boarding parties to board enemy ships. Energy barriers are present on Covenant boarding craft, on the end of the craft's penetration tip. Energy barriers are also used as exterior doors in hangar bays on Covenant starships. The barriers can also be configured to block all vehicles or personnel or allow them to pass through when required. It is interesting to note that Covenant signal units work through Covenant energy barriers, while human COM units do not.
By 2552, the UNSC had also begun to employ energy barrier technology in their space installations and ships in a fashion similar to the Covenant. Examples of human energy barriers include the Sabre engineering facility on the orbital dockyard Anchor 9, and the windows of the Charon-class light frigate UNSC Forward Unto Dawn. As the most advanced warship in the Fleet, the hangar bays of the UNSC Infinity are also equipped with energy barriers.
In the Halo games, energy barriers are typically encountered in levels featuring a Covenant ship.
In Halo: Combat Evolved, it is possible to operate the shuttle bay doors of the Truth and Reconciliation. On the level The 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 the player can escape in a Spirit with Keyes.
In Halo: Reach, on the Covenant corvette Ardent Prayer in the level Long Night of Solace, the shields operate in a different fashion: after Noble Six presses a button, the shields still remain in place over the bay, but ships can now go in and out of them. Presumably they are simply lowered to a point things could travel through them while remaining in place to hold the atmosphere in the bay as the ship is in space.
 List of appearances
- Halo: Combat Evolved (First appearance)
- Halo: First Strike
- Halo 2
- Halo 3
- Halo: Contact Harvest
- Halo Legends
- Halo: Reach
- Halo 4
- ^ Halo: Contact Harvest, page 98
- ^ Halo: Contact Harvest, page 309
- ^ Halo 2, level Cairo Station
- ^ Halo: Combat Evolved, campaign level, The Truth and Reconciliation
- ^ Halo: Reach, campaign level, Long Night of Solace
- ^ Halo: Contact Harvest, page 99
- ^ Halo: Contact Harvest, page 132
- ^ Halo: Reach, multiplayer map, Anchor 9
- ^ Halo 4, campaign level Dawn
- ^ Spartan Ops: S1E10 Exodus
- ^ Halo: Reach, campaign level Long Night of Solace