This sounds like a riddle or a reference to a fictional story! There's no real gas that would cause a professor's voice to change.

Here's why:

* Voice change mechanisms: Voice changes happen due to physical changes in the vocal cords, not gas inhalation. These changes can be caused by things like:

* Illness: Infections, allergies, or other medical conditions can affect the vocal cords.

* Hormones: Puberty causes changes in voice due to hormone shifts.

* Vocal overuse: Yelling, singing loudly, or prolonged talking can strain the vocal cords.

* Gases and the body: Most gases we encounter are either harmless (like oxygen) or dangerous in high concentrations (like carbon monoxide). There's no known gas that selectively alters the vocal cords for voice change.

If you're thinking of a specific story or scenario, please tell me more so we can explore the fictional context!