A gas grenade or generating canister was a hand-held projectile weapon used for incapacitating an enemy. When activated and thrown, it released a gas of some kind into the area. A gas grenade could be non-lethal or very lethal, depending on the gas it released, and on the physiology of the target. It differed from a smoke grenade in that the former was meant to incapacitate, while the latter was intended to reduce visibility.
In 2268, Leonard McCoy used a container of baking soda as a component of a non-lethal gas grenade in an attempt to escape the Melkotian illusion. Cotton wadding was also added by Spock. (TOS: "Spectre of the Gun")