stop. In the European Union, most types of machinery are required to be equipped with an emergency stop according to the Directive 2006/42/EC. Exceptions apply for machinery in which an emergency stop would not lessen the risk as well as for portable hand-held/hand-guided machinery. Nuclear power plants A kill switch in a nuclear reactor plant is called SCRAM. It is usually characterized as an acronym for "safety control rod axe man", though this is probably a backronym. Machine tools Emergency stop functions are frequently used on machine tools, including equipment like wood and metal sawing machines, grinding machines, drilling machines, milling machines and machining centres and lathes. The emergency stop safety function, and general requirements for emergency stop devices are set out in ISO 13850. Machine specific (type-C) standards often include specific requirements for the emergency stop functions, but in the absence of a relevant type-C standard, the risk assessment should be used to determine whether or not an emergency stop function would be useful in avoiding or limiting harm. The ISO machinery safety standard types are defined in ISO 12100, and this nomenclature is used by other standards development organizations, like ANSI in the USA, and CSA in Canada. Complementary protective measure A machinery's emergency stop control is considered a complementary protective measure because it is intended to complement the primary safeguarding measures like fixed guards, movable interlocked guards or safeguarding devices. The primary safeguarding measures prevent injury automatically, either by enforcing distance between a hazard and a person, or by eliminating the hazard by stopping hazardous motion or switching off a source of hazardous energy. By contrast, emergency stop requires a deliberate action on the part of a person who must first recognize that some hazardous condition is about to arise or is arising, and who then must activate the emergency stop function by pressing the emergency stop button or activating another emergency stop device such as a pull-cord switch. Fuel stations and road vehicles A kill switch is also used for gasoline pumps or any other device that pumps large amounts of explosive or flammable chemicals. There is commonly a single kill switch for all pumps at a pumping station. Elevators and escalators Elevatorsoften have a red two-way button on the control panel which is either marked "Emergency Stop" or "Run/Stop". Normally, the button is in the "up" or unpushed position, allowing the elevator to "run" in