Natives with no fear of CO2?

http://www.openpassageexpedition.com/blog.htm

The village was eerily quiet; a ghost town bathed in a pristine other-worldly light that made even the decayed and abandoned vehicles glow with an ethereal beauty. The only sound came from ATV's whirring in every direction. Nobody, it appeared, walked in this town of TK people, who seemed permanently affixed to their four-wheelers like droids cruising some distant post-human outpost, sun glinting off their black helmets.