A smoke grenade (2370)
A smoke grenade is a non-lethal bomb that gives off thick smoke when it explodes. They are usually used to provide cover in the form of a smoke-screen.
In 2370, an unnamed Starfleet officer threw a smoke grenade to provide cover for Chief O'Brien and Li Nalas after they were pinned down in the promenade security office, during General Krim's take-over of Deep Space 9. (DS9: "The Siege")