It is interesting that we now have the gas coming from the tunnel...

Going way back to when ground zero was first encountered by Victor and Pegs, we speculated that it might be an area denial weapon. A defensive measure to keep things away from a valuable facility. When Victor and Saul go back, they do not notice any animals, they see undisturbed dead bodies, even the trees were brown. They also observed blood stains indicating previous violence. CJ later states that one of her explores may have been changed by the gas exposure. @@ On an aside, I still think CJ sabotaged the tanks. She explicitly tells Saul which color tank to use! If there was no difference a priori, why assign a color? @@

We get additional complexity when Victor and Tanya go back the gas is gone and the area is more normal. However, the gas returns shortly after Tanya's gunshot. So, was the localized tremor and gas release just chance coincidence or a defensive measure? Fast forward to the present, the tunnel entrance that Michael, Victor and Datu used is now closed and the tunnel they are at now has gas. So, again, is this a defensive measure or just chance?