The fire-suppression system was a system on starships and starbases that used foam to smother the flames. It was programmed to function automatically; failing that, it could be activated using a tricorder.
Kirk and Spock activated this system to put out various fires caused by the Gorn attack. They also located a Gorn intruder who was using a personal cloaking device to evade capture. The foam revealed the outline of the Gorn, allowing them to see and fire on him. (TOS video game: Star Trek)