Why do i sometimes smell anesthesia?

It's likely gas: Most general anesthetics are maintained by inhaling a potent vapor or "gas", despite an IV med usually being used to put you to sleep. As you awaken, the gas diffuses out of your blood stream via your lungs and you may smell the gas as you exhale it. Some IV medications may also cause you to perceive a taste or smell as they take effect in your brain, even though there's nothing in your mouth.

Anesthetic gas: The three most use inhalation anesthetic agents are: Isoflurane, Sevoflurane and Desflurane. All of them smell especially in high concentration. Most adult patients undergo general anesthesia do not smell it because they are induced to sleep by intravenous agents first.