In the first part of this mission when you are using the fire weapon, the game is REALLY bad at determining when you are in an oxygen environment.
Example 1: Go to the Troll Booth and trigger the dome. Even though both you and an enemy are in the air dome, your Oz kit is not in place, AND the enemy is clearly in flames, Janey nags about fire not working in a vacuum.
Example 2: Go to the Darksiders Garage. Set fire to an enemy in the connecting tunnel, or lure them back to where the Moon Zoomy station and fast travel are, and their being on fire does not count. Repeat the annoying nag about being in an atmosphere.
This happens on ALL levels, with ALL characters. Basically, the game can tell you are in an atmosphere as far as an oz kit is concerned, but is completely clueless about the scavs; you pretty much have to set fire to them ONLY in specific locations, which is really annoying.