A kill switch, also known as an emergency stop (E-stop), emergency off (EMO) and as an emergency power off (EPO), is a
safety
Safety is the state of being "safe", the condition of being protected from harm or other danger. Safety can also refer to risk management, the control of recognized hazards in order to achieve an acceptable level of risk.
Meanings
There are ...
mechanism used to shut off machinery in an emergency, when it cannot be shut down in the usual manner. Unlike a normal shut-down switch or shut-down procedure, which shuts down all systems in order and turns off the machine without damage, a kill switch is designed and configured to abort the operation as quickly as possible (even if it damages the equipment) and to be operated simply and quickly (so that even a
panic
Panic is a sudden sensation of fear, which is so strong as to dominate or prevent reason and logical thinking, replacing it with overwhelming feelings of anxiety and frantic agitation consistent with an animalistic fight-or-flight reactio ...
ked operator with impaired
executive functions
In cognitive science and neuropsychology, executive functions (collectively referred to as executive function and cognitive control) are a set of cognitive processes that are necessary for the cognitive control of behavior: selecting and succe ...
or a bystander can activate it). Kill switches are usually designed to be noticeable, even to an untrained operator or a bystander.
Some kill switches feature a removable, protective barrier against accidental activation (e.g. a plastic cover that must be lifted or glass that must be broken), known as a
mollyguard. Kill switches are features of mechanisms whose normal operation or foreseeable misuse might cause injury or death; industrial designers include kill switches because damage to or the destruction of the machinery is less important than preventing workplace injuries and deaths.
A similar system, usually called a
dead man's switch, is a device intended to stop a machine (or activate one) if the human operator becomes incapacitated or leaves the machine unattended, and is a form of fail-safe. They are commonly used in industrial applications (e.g.,
locomotive
A locomotive or engine is a rail transport vehicle that provides the Power (physics), motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, Motor coach (rail), motor ...
s, tower cranes,
freight elevators) and consumer applications (e.g.,
lawn mowers, tractors,
personal watercraft
A personal watercraft (PWC), also called water scooter or jet ski, is a recreational watercraft that a rider sits or stands on, not within, as in a boat. PWCs have two style categories, first and most popular being a runabout or "sit down" whe ...
, outboard motors,
snow blowers,
motorcycle
A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...
s and
snowmobiles). The switch in these cases is held by the user, and turns off the machine if they let go. Some riding lawnmowers have a kill switch in the seat which stops the engine and blade if the operator's weight is no longer on the seat.
Vehicles
On
railways
Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a pre ...
, an emergency stop is a full application of the
brakes
A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction.
Background ...
in order to bring a train to a stop as quickly as possible. This occurs either by a manual emergency stop activation, such as a button being pushed on the train to start the emergency stop, or on some trains automatically, when the train has
passed a red signal or the driver has failed to respond to warnings to check that they are still alert, which is known as a
dead man's switch. A similar mechanism is the
watchdog timer.
In large ships, an emergency stop button pulls the countershaft for the fuel pumps to the stop position, cutting off the fuel supply and stopping the engines. With a controllable-pitch propeller, the stop button may declutch the engine from the propeller.
NASCAR
The National Association for Stock Car Auto Racing, LLC (NASCAR) is an American auto racing sanctioning and operating company that is best known for stock car racing. The privately owned company was founded by Bill France Sr. in 1948, and hi ...
requires all their stock cars to be equipped with a
steering wheel
A steering wheel (also called a driving wheel (UK), a hand wheel, or simply wheel) is a type of steering control in vehicles.
Steering wheels are used in most modern land vehicles, including all mass-production automobiles, buses, light and ...
-mounted kill switch, in case the
accelerator pedal
Car controls are the components in automobiles and other powered road vehicles, such as trucks and buses, used for driving and parking.
While controls like steering wheels and pedals have existed since the invention of cars, other controls have ...
sticks and the driver needs to shut down the engine.
Kill switches are also used on land vehicles as an
anti-theft system and as an emergency power off. Such devices are often placed in
bait cars and configured so that observing police can trigger the switch remotely.
A related concept is the
dead man's switch, where the operator must be holding a button or lever any time the vehicle is operating. A common example of this is the kill switches used by
boat
A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats.
Small boats are typically found on inl ...
ers and
jetskiers wherein a cord connects the kill switch to the operator (usually by the operator's
life jacket
A personal flotation device (PFD; also referred to as a life jacket, life preserver, life belt, Mae West, life vest, life saver, cork jacket, buoyancy aid or flotation suit) is a flotation device in the form of a vest or suite that is worn by a ...
or clothing), and if the operator is thrown overboard in an accident, the cord will pull the switch and immediately shut down the vessel's engine. This prevents it from becoming a runaway vessel that could impose a danger to other vessels or swimmers at sea, and allows the operator to swim back to the vessel and re-board it without the risk of being injured by the boat's propeller. A similar device is featured on most lawnmowers: a lever on the handle either disables the ignition system and applies a brake to the flywheel (on a gasoline lawnmower), or cuts the power to the motor (on an electric lawnmower), as long as it is not held down.
Monster Truck Racing Association requires all of their
monster trucks to be equipped with kill switches (either remote or in cab), in case the monster truck loses control and the driver needs to shut off the engine. Monster trucks' kill switches are tested before races.
Pioneer-era planes and World War I aircraft
Early aviators using
rotary engine-powered aircraft from
the beginnings of their use in 1908, up through the end of
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
in 1918 had what could be called a reversed functionality version of the "dead man's switch" for cutting the
ignition
Ignition may refer to:
Science and technology
* Firelighting, the human act of creating a fire for warmth, cooking and other uses
* Combustion, an exothermic chemical reaction between a fuel and an oxidant
* Fusion ignition, the point at which a ...
voltage to the spark plugs on such a power-plant, to give a degree of in-flight speed control for a rotary engine. This was often called
a "blip switch" or "coupe switch" (from the French term ''coupez'', or "cut") and when not being pressed, allowed the high voltage from the engine's
magnetos to operate the ignition with normal engine operation in flight — pressing the "blip switch" cut the flow of high voltage from the magnetos, stopping the combustion process in the cylinders. When such a "blip switch" was intermittently used on landing approach, this allowed a limited degree of engine speed control, as rotary engines generally did not have a conventional
throttle
A throttle is the mechanism by which fluid flow is managed by constriction or obstruction.
An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term ''throttle'' ...
in their
carburettors to regulate engine speed, but only for governing the fuel-air ratio for start-up and full-speed operation.
Industrial machinery
![Emergency stop button](https://upload.wikimedia.org/wikipedia/commons/d/df/Emergency_stop_button.jpg)
On large industrial machines, an emergency stop button is typically located on the panel, and possibly in several other areas of the machine. Often, an emergency stop is made wireless using a remote control. This provides a rapid means to disconnect the energy source of the device to protect workers. For fail-safe operation, the emergency stop button is a normally closed switch, which ensures that a broken wire will not prevent it from being activated, but may accidentally activate the emergency stop.
In the
European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...
, 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
A backronym is an acronym formed from an already existing word by expanding its letters into the words of a phrase. Backronyms may be invented with either serious or humorous intent, or they may be a type of false etymology or folk etymology. The ...
.
Machine tools
Emergency stop functions are frequently used on
machine tools
A machine tool is a machine for handling or machining metal or other rigid materials, usually by cutting, boring, grinding, shearing, or other forms of deformations. Machine tools employ some sort of tool that does the cutting or shaping. All m ...
, including equipment like wood and metal
sawing machines,
grinding machines
Grind is the cross-sectional shape of a blade.
Grind, grinds, or grinding may also refer to:
Grinding action
* Grinding (abrasive cutting), a method of crafting
* Grinding (dance), suggestive club dancing
* Grinding (video gaming), repetitive and ...
,
drilling machines
A drilling rig is an integrated system that drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to drill wat ...
,
milling machines and machining centres and
lathes. The emergency stop
safety function
Safety is the state of being "safe", the condition of being protected from harm or other danger. Safety can also refer to risk management, the control of recognized hazards in order to achieve an acceptable level of risk.
Meanings
There are ...
, 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
CSA may refer to:
Arts and media
* Canadian Screen Awards, annual awards given by the Academy of Canadian Cinema & Television
* Commission on Superhuman Activities, a fictional American government agency in Marvel Comics
* Crime Syndicate of Amer ...
in Canada.
Complementary protective measure
![Homemade Mollyguard](https://upload.wikimedia.org/wikipedia/commons/1/12/Homemade_Mollyguard.jpg)
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
An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...
or
flammable
A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable mat ...
chemicals. There is commonly a single kill switch for all pumps at a
pumping station
Pumping stations, also called pumphouses in situations such as well drilling, drilled wells and drinking water, are facilities containing pumps and equipment for pumping fluids from one place to another. They are used for a variety of infrastru ...
.
Elevators and escalators
Elevator
An elevator or lift is a wire rope, cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or deck (building), decks of a building, watercraft, ...
s often 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 normal service. When the button is pushed, the elevator comes to an immediate stop. When the button is pulled back out, it resumes normal service, thus the reason for the use of the phrase "Run/Stop".
Escalator
An escalator is a moving staircase which carries people between floors of a building or structure. It consists of a motor-driven chain of individually linked steps on a track which cycle on a pair of tracks which keep the step tread horizo ...
s will typically have a key-operated control that will turn the escalator off, or change its direction to up or down. Next to the key switch will be a red "Emergency Stop" button, which is used in the event of equipment failure, or where there is a potential for injury, such as when someone's shoe gets stuck in the "comb" at the top or bottom of the escalator and there is a risk of serious injury. The key switch is used to return the escalator to service after it has been stopped.
Gym
Treadmill
A treadmill is a device generally used for walking, running, or climbing while staying in the same place. Treadmills were introduced before the development of powered machines to harness the power of animals or humans to do work, often a type of ...
s often use a safety key with one end magnetically attached to the machine and the other end clipped to the user's waist. If the safety key is pulled out, such as in the event of a fall, the treadmill stops immediately. In other cases, some other treadmills have a more traditional kill switch, often mounted towards the rear of one of the hand railings.
Amusement rides
The emergency stop on an
amusement ride is similar to that on industrial equipment. Typically brakes on a ride are designed to be disengaged when power is applied; disconnecting power will cause all brakes to engage. Most amusement rides have a computer that can, similar to the rail example provided above, engage the emergency stop when such a ride is determined to be out of operating specification, or an accident involving a passenger or ride employee has happened.
Software
: ''See also
Brick (electronics) – an electronic device that can no longer function''
By analogy to physical kill switches, "kill switch" can be used to refer to a mechanism incorporated in software that can be activated by its manufacturer or licensor, for example if the product is withdrawn, or a maintenance fee has not been paid, or a device has been lost or stolen. It can also refer to kill switches for the stopping of
malware
Malware (a portmanteau for ''malicious software'') is any software intentionally designed to cause disruption to a computer, server, client, or computer network, leak private information, gain unauthorized access to information or systems, depri ...
such as in the
WannaCry ransomware attack.
There is a debate about implementing kill switches in
robot
A robot is a machine—especially one programmable by a computer—capable of carrying out a complex series of actions automatically. A robot can be guided by an external control device, or the control may be embedded within. Robots may be c ...
s and advanced
artificial intelligence
Artificial intelligence (AI) is intelligence—perceiving, synthesizing, and inferring information—demonstrated by machines, as opposed to intelligence displayed by animals and humans. Example tasks in which this is done include speech re ...
systems.
Smartphones
In
smartphones
A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, which ...
, a kill switch is a security feature that allows the phone's owner to remotely render the smartphone inoperable if it is lost or stolen. From 2015 this feature is legally required in
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
for smartphones.
There are also ''hardware kill switches'' on some phones, such as
PinePhone, where the user can, by moving a hardware switch inside the phone, disable hardware like the camera, microphone, Wi-Fi or LTE.
Military and other equipment
It is thought that some electronic chips used in equipment, particularly military, have a secret "kill" function that disables the equipment. It has been reported that French and Israeli
electronic warfare
Electronic warfare (EW) is any action involving the use of the electromagnetic spectrum (EM spectrum) or directed energy to control the spectrum, attack an enemy, or impede enemy assaults. The purpose of electronic warfare is to deny the opponen ...
units have used kill switches to disable opponents' military systems. And systems have been infected with malware specifically designed to damage them.
John Deere
Deere & Company, doing business as John Deere (), is an American corporation that manufactures agricultural machinery, heavy equipment, forestry machinery, diesel engines, drivetrains (axles, transmissions, gearboxes) used in heavy equipment, ...
tractors have been criticised for it being impossible for owners to service or repair them; only John Deere has access to computer code required for this and to accept non-John-Deere replacement parts. Vital equipment from other manufacturers such as critical medical equipment has similar restrictions. Remote locking by the manufacturer may also be possible. It was reported that during the
2022 Russian invasion of Ukraine
On 24 February 2022, in a major escalation of the Russo-Ukrainian War, which began in 2014. The invasion has resulted in tens of thousands of deaths on both sides. It has caused Europe's largest refugee crisis since World War II. An ...
Russian troops stole Ukrainian farm equipment, but that the dealers who owned the equipment locked it remotely.
Spaceflight
Range safety systems can automatically destroy errant vehicles in-flight. Range-safety officers may also manually destroy vehicles; this method was used to destruct errant
solid rocket boosters in the
Space Shuttle Challenger disaster
On January 28, 1986, the broke apart 73 seconds into its flight, killing all seven crew members aboard. The spacecraft disintegrated above the Atlantic Ocean, off the coast of Cape Canaveral, Florida, at 11:39a.m. Eastern Time Zone, EST (1 ...
.
See also
*
*
*
*
*
* a fast kill switch for table saws triggered by electrical conductivity of user's finger.
* the opposite of a kill switch, where a system is designed to operate even if damage or injury will occur.
References
{{DEFAULTSORT:Kill Switch
Safety switches