re: like todays doping tests for races.
There’s no way a person could inhale enough helium to float or lift themselves. (Couldn’t retain it, either. Helium goes through the glass walls of He Ne laser tubes over time, meaning that the gas has to be recharged occassionally.) Balloons work by being less dense overall than air, and given the low density of air, it takes a large volume of helium in a balloon to generate enough lift to lift a human.