Methane tank
From Halopedia, the Halo wiki
Methane Tank
The Methane Tank is a device that the Grunts use because they can't breathe air like the other species of the Covenant.
The Heretic Grunts can be seen with a more visable Methane Tank.
Without Methane Tank
A Grunt is not seen in the games without the tanks. However, out of their Methane Tank, they look as pictured right.
File:Grunt.jpg
A Grunt without their Methane Tank
