From Halopedia, the Halo wiki
Atmosphere pits are Covenant structures filled with methane. Typically deployed on Covenant bases or military camps in the field, they are designed to allow Unggoy to have a space to live without being hooked up to their methane tanks. Essentially similar in purpose to the starship-based methane suite, atmosphere pits come in different shapes and types, including a dome-shaped tent made from a flimsy white material, allowing the pit to be easily erected and collapsed in the field, and a cylindrical, tank-like structure. They are equipped with airlocks to keep the methane inside.
List of appearances
- Halo: The Flood (First appearance)
- Halo: First Strike