Nitrous oxide

Nitrous oxide (also referred to as laughing gas) is a gaseous substance that is used as an anesthetic to render medical patients unconscious prior to surgery.

Empath: The Luckiest Smurf stories
Nitrous oxide is used by Dentist Smurf in his dental surgery in the EMPATH: The Luckiest Smurf story series. He is very careful of how to administer the gas to his patients, as too much uncontrolled use of the gas could cause Dentist to have laughing fits and to pass out before he could perform any surgery.