By the Doctor's calculations, there should be enough air for another few hours at least, long enough for him to find the TARDIS. And if he could find the generators or some kind of control room, he could restore the power and there'd be no need to leave after all. Which would be preferable with the TARDIS nowhere in sight.
He scratched his nose as he walked; there was a pungent smell that tickled just a little and a strange kind of gas that was beginning to make his eyes water. But what was more important, leaving the base? Or finding the TARDIS?