Full context:   Fire is one of the four classical elements and has been used by humans in rituals, in agriculture for clearing land, for cooking, generating heat and light, for signaling, propulsion purposes, smelting, forging, incineration of waste, cremation, and as a weapon or mode of destruction. Various technologies and strategies have been devised to prevent, manage, mitigate, and extinguish fires, with professional firefighters playing a leading role. For example, most home fires start from unattended cooking, although cigarettes are a major cause. Smoke detectors and sprinkler systems greatly reduce harm from home fires.