If one fire sprinkler head is activated, will they all go off?

Contrary to what you see in movies, every sprinkler in a building does not have to go off when one goes off. Each sprinkler head has its own sensor that activates the sprinkler when high heat is detected. Fire sprinklers actually can save a lot of water. Because only one goes off at a time, the water is very focused on putting out the actual fire and much less goes to waste than would from the fire department using a fire house to extinguish the fire. This means the fire is put out more quickly, less property damaged by water, and less water wasted.