The gas most commonly known for making your voice temporarily deeper is sulfur hexafluoride (SF₆). It is very dense, so sound travels more slowly through it than through normal air, which shifts the resonant frequencies in your vocal tract downward and makes your voice sound unusually low for a few seconds. However, deliberately inhaling any gas for this effect is not safe and strongly discouraged:

  • SF₆ can displace oxygen in your lungs and lead to suffocation if you don’t clear it properly.
  • Other “deep voice gases” mentioned online (like xenon, chloroform, bromine, carbon tetrachloride, or even butane) range from anesthetic to highly toxic or flammable.
  • Repeated or careless use in stunts or “science pranks” has real risk of lung injury, unconsciousness, or worse.

If you like the deep-voice effect, the safe way to get it is with audio filters or voice-changing apps , not by breathing unusual gases.