@betty Small correction from a scientist. At 50% oxygen content, everything that is flammable (including us humans, clothing, animals, plants) would immediately start to burn. Up there, the air also has just under 21% oxygen content (the same as at the sea). Only the air pressure is correspondingly lower (or the density is lower) and therefore less oxygen is available with each breath. Therefore, an appropriate breathing technique is very helpful!
Very easy for mountaineering. Perhaps that is why many people underestimate it. The altitude is tough.
The lake below the pass was still covered in deep snow. So we didn't go swimming (swimming is supposed to wash away bad karma) There isn't another teahouse until after the pass. So take plenty of water with you!