Gas Container
From Halopedia, the Halo Wiki
Gas Containers are used in Forerunner mining facilities to move the volatile gas mazes from location to location within the facility. They can detonate if exposed to weapons fire or an explosion in their immediate vicinity. The gas inside these containers is possibly methane; it appears to be similar in color to that of which the Unggoy have on their backs.[1]
[edit] Gameplay
In Halo 2, they can be used to kill Heretic forces on the level The Arbiter and The Oracle. They also spawn in Halo 2 on the Multiplayer level Colossus. Also these containers are better to use when there are groups of enemies to damage their energy shields for an easier kill. The substance could also be a possible fuel used to power the station and the containment shields of the Flood perimeter.[1]
