Like for all inert gases, the psychoactive effects of xenon begin only above a certain pressure threshold (i.e. concentration threshold). The heavier an inert

Like for all inert gases, the psychoactive effects of xenon begin only above a certain pressure threshold (i.e. concentration threshold). The heavier an inert gas is, the lower the pressure threshold. So for nitrogen the pressure threshold is well above atmospheric pressure and it affects only the divers who must breathe air at a pressure equal to their ambient pressure. Lighter inert gases, like helium, can be used up to higher pressures, corresponding to greater depths. For xenon, the heaviest non-radioactive inert gas, the pressure threshold is much lower, so it can work as a general anesthetic at atmospheric pressure. However, at the low pressures corresponding to the high altitudes around Everest, perhaps xenon does not have any psychoactive effects, which is actually claimed by the company providing the climbers with it.