[Rane Longfox]

Just to sort out this "fire" thing.

The Doctor calibrated the atmospheric converter so that it only affected the Sontaran clone gas. While this is a somewhat unlikely piece of technology, it's quite a step more realistic than say, a time-travelling police box, or a field to disable guns by expanding the bullets.
I'm assuming that they have at least traces of this gas floating around the Sontaran ship also, though well below human-toxic levels, hence why they could blow up the ship with same piece of equipment.


So no, it was not normal oxygen-burning fire.