Neurazine gas
From Memory Alpha, the free Star Trek reference
Neurazine gas is a type of gas that can be used to incapacitate humanoids. It was used aboard Dominion starships.
In 2375, Kira Nerys planned to use neurazine gas to immobilize the Breen engineers who were installing an energy dissipator weapon on a Jem'Hadar fighter. However, she and the Cardassian Rebellion members had to wait until the Breen were finished installing it before they could flood the ship with the gas. (DS9: "Tacking Into the Wind")
