Why do they it’s wierd
Because they breathe methane and would suffocate in oxygen-rich atmospheres.
The Unggoy’s homeworld has a methane atmosphere and they can’t breathe oxygen. Thus they have packs that contain methane to allow them to do their work in oxygen-rich places.
They act like oxygen tanks that we humans use, but with methane instead. Like the other two posters before me said, they can only survive in methane environments since their species evolved in a methane rich environment on their homeworld.
Please do not discriminate against methane breathers. Thanks.
They breathe methan instead of oxygen.
They breathe fart gas
It makes breathing easier, I believe that they can get Methane naturally, but it causes labored breathing.
Methane tanks. Simulated pressure and composition of the native Ungoy home world.
To breathe
In addition to breathing, they are absolutely necessary for making it even funnier and more satisfying when they die.
I have no idea I guess it was 343 take on them
> 2535452892661946;12:
> I have no idea I guess it was 343 take on them
It’s not a 343 addition; Grunts have always had the gas tank backpacks.
> 2535437652903765;13:
> > 2535452892661946;12:
> > I have no idea I guess it was 343 take on them
>
> It’s not a 343 addition; Grunts have always had the gas tank backpacks.
Oh ok haven’t play the halo games in since I was a and I’m only just know getting back into them so my memory is a bit rusty. 
Dey breeve dat gas, mang.
If I ever correctly it’s so they can breathe in the air around them. The atmosphere from their home world is a lot different to my knowledge.
Because the covenant enslaved them to fight for them. The atmosphere on their home world is different on the planets they fight on so they need support