Fire extinguishers or manual extinguishers were hand-held devices containing a substance used to extinguish a fire.
They were typically located in easily accessible areas, such as the bridge and corridors of a starship. (Star Trek VI: The Undiscovered Country)
Bajoran sub-impulse fighters were equipped with fire extinguishers. In 2371, Lieutenant Jadzia Dax attempted to use one to put a fire out in a plasma conduit, but it was empty. The fighter subsequently crashed on the surface of Bajor. (DS9: "The Siege")
In 2375, the USS Rio Grande, carrying Odo and Weyoun 6, was attacked by several Jem'Hadar fighters. During the engagement, the runabout interior caught fire. Weyoun, using a manual extinguiser, put the fire out. (DS9: "Treachery, Faith and the Great River")
Later the same year, during the Second Battle of Chin'toka, Ensign Nog reported that the fire-suppression system aboard the USS Defiant went down. Worf told him to use a manual extinguisher. (DS9: "The Changing Face of Evil")