If the fire spreads, more sprinklers go off, but the sprinklers do not automatically flood an entire building, only in areas where heat is high. Sprinklers have been in use in the United States since 1874.
Cost of sprinklers runs from $2 to $3 a square foot (2002 prices), roughly the same as carpet or tile. They can be installed during construction or retrofitted. More than 200 communities, half of them in California have laws requiring residential sprinkler system. Many cities require them for large commercial buildings and places of assembly.
According to the National Fire Protection Association, fires in hotels with sprinklers averaged 78% less damage than fires in hotels without them (1983-1987). The NFPA says the average loss per fire in buildings with sprinklers was $2,300, compared to an average loss of $10,300 in unsprinklered buildings.
The NFPA states that it "has no record of a fire killing more than two people in a completely sprinklered building where a sprinkler system was properly operating, except in an explosion or flash fire or where industrial fire brigade members or employees were killed during fire suppression operations."