Methane Tanks are back-mounted containers used by the Covenant Unggoy, fixed onto their Combat Harness. When they are of the large variety, they provide a place for the creatures to breathe their Methane atmosphere outside of their suits. Thus, Unggoy remove their suits when entering the huge methane filled tank, as they are not needed.
The Covenant also created special methane chambers for Unggoy when they are not in battle. There is a main chamber for the Unggoy to reside in and a smaller chamber in front where the Unggoy can change into and out of their suits. These structures often have posted guards and airlocks at their entrances. A number of different types of methane chamber exist: the atmosphere pit, a more temporary version, and the Methane Suite, a ship-board variant.
- When shot in Halo Wars, the tanks sometimes explode due to methane's high flammability.
- In Halo: Reach, when a Methane Tank is shot off, it will send the Unggoy flying through the air. There is also more variety in the tank designs between different Unggoy ranks.
- In reality, methane is colorless. The blue color used in the games may have just been used as an artistic choice in order to allow the player to actually see it.