Many officials, architects, and building owners think the main function of a sprinkler system is to protect lives. To offset the cost of the sprinklers, they convince building officials to eliminate the expensive life safety requirements that have protected people for years. They argue that sprinklers put out fires right away so fire-resistant doors and walls aren't needed. But sprinklers don't spray water unless flames make the temperature hot enough to fuse the sprinkler head. Many fires smolder a long time before producing flames or much heat. Smoke inhalation, not fire, causes more than 80 percent of all fire deaths. In contrast, fire-resistant doors and walls seal off fire--and smoke. People can escape along a safe path or wait in a protected room until firefighters rescue them. This built-in fire resistance is never out-of-order. Sprinklers alone do not save lives in a fire situation. They should not be a substitute for fire-resistant construction.