This is a video of Cody from Cody’s Lab breathing in sulfur hexafluoride and then perfluorobutane and then trying to talk. Both are much denser than oxygen and they end up acting in the opposite way of helium, making your voice deep instead of high.

The resulting voice is pretty insane sounding, though I was a little scared he wouldn’t actually be able to clear the perfluorobutane from his lungs and he’d end up dying on camera while screaming for help in a hilariously deep voice.

Keep going for the full video.

Source: Geekologie – Guy breathes in the deeper voice gas and things get weird