Since the inception of the first sprinkler system in the 1870s, the focus of most sprinkler systems has been to control a fire rather than to extinguish it. Although sprinkler systems have extinguished numerous fires, sprinkler systems generally are designed to limit the size of a developing fire and prevent it from growing and spreading beyond its general area of origin. In some cases, fires are shielded from sprinkler system discharge, which makes complete extinguishment difficult. A sprinkler system’s ability to extinguish or suppress a fire has not been widely discussed until fairly recently, because the interaction between sprinkler discharge and a fire had not been sufficiently understood. Phenomena associated with fire growth rates, mass loss of the burning fuel package, and rate of heat release produced by a fire need to be considered. Only within the past two decades have research efforts provided a greater understanding of these phenomena. The result is the development of nontraditional sprinkler devices such as the control mode specific application (CMSA) sprinkler and the early suppression fast-response (ESFR) sprinkler.