From Halopedia, the Halo wiki
The methane suite is a section aboard Covenant ships where Unggoy soldiers can live in a methane-filled environment while not supported by the pressurized methane provided by their suits' methane tanks. Dadab describes the suite of the missionary ship Minor Transgression as being a box-like room with triangular depressions in the wall and as stale as the methane in their tanks; compressor stations for refilling Unggoy portable methane tanks. The room also features a food nipple.
List of appearances
- Halo: Contact Harvest (First appearance)
- Halo: Contact Harvest, page 53
- Halo: First Strike, page 27