You also need to stabilize your head and the while body so that you do not leave the bucket for a longer time (to ensure death). I assume that helium would not

You also need to stabilize your head and the while body so that you do not leave the bucket for a longer time (to ensure death). I assume that helium would not have the alert effect CO2 has - similarly to nitrogen which is probably too Henry to just it with a bucket as you describe.