In brief
The emergency stop button is a complementary measure that stops a machine as quickly as possible in a dangerous situation without creating additional risk; it does not replace guards or lockout and tagout. It has a red actuator on a yellow background and latches when pressed; releasing the latch does not restart the machine, it only allows it to be restarted. Its function is tested regularly and the result recorded.
Where does the emergency stop button appear in the legislation?
When a press operator's glove catches in the die, when a conveyor worker's arm is drawn into the drum, or when a part slips out of its clamping fixture on a CNC machine, there is only one thing that can be done in the first seconds: stop the machine. The emergency stop button is designed for those first seconds. Its rules come from two regulations.
For the employer as user: Annex I of the Regulation on Health and Safety Requirements for the Use of Work Equipment requires:
- All work equipment has a system that can stop the equipment completely and safely; stop controls take priority over start controls (2.3).
- If the hazards of the equipment and its normal stopping time make it necessary, there is an emergency stop system (2.4).
- Equipment that has stopped for any reason is restarted only by deliberate use of a control designed for that purpose (2.2.1).
For the manufacturer: Annex I 1.2.4.3 of the Machinery Safety Regulation (2006/42/EC) of 3 March 2009 requires the emergency stop device to be clearly identifiable, clearly visible and quickly accessible; to stop the hazardous process as quickly as possible without creating additional risks; to remain latched once activated until it is specifically released; and for its release not to restart the machinery but only to permit restarting. The same item states explicitly that the emergency stop is a back-up measure that does not replace other protective measures. We explain the transition timetable to the new regulation that comes into force for new machinery on 20 January 2027 in our article on the machinery safety regulation.
Emergency stop colour and types
The emergency stop colour is set by standard: under TS EN ISO 13850, the actuator of an emergency stop control is red, and the background behind it, where there is one, is yellow. This colour combination is used only for emergency stops. Making normal stop, reset or start buttons red and yellow leads to the wrong button being pressed in a panic.
| Type | Where is it used? | Point to watch |
|---|---|---|
| Mushroom-head button | Control panels, operator stations | Latches when pressed; released by turning or pulling |
| Pull wire (rope switch) | Long conveyors, belt lines | Wire tension and operation when pulled from either end |
| Button on a portable control | Crane pendant, robot teach pendant | If the control is wireless, the machine stops when the connection is lost |
If an e-stop button's head is broken, has tape wrapped around it, has faded or has lost its yellow background label, the button is considered defective and is replaced.
Emergency stop location: where does it go?
When deciding the emergency stop location, the only criterion is whether a hand can reach it in a dangerous situation. These rules make the job easier:
- At least one at every operator station. The operator must be able to reach the button without reaching into the danger zone.
- At every point where the machine is entered. Maintenance doors, material feed and discharge points.
- At intervals on long lines. Everyone working along a conveyor or belt line must be able to reach a button or pull wire by stretching out an arm.
- Clear and visible. No crates, pallets or materials are placed in front of the button. A button hidden behind a guard or on the side of a panel is useless.
- Protected against accidental operation but not obstructed. Where necessary it can be surrounded by a collar; it is not covered with a lid.
| Machine | Recommended location |
|---|---|
| Hydraulic press | Operator control panel, rear feed side |
| CNC machine | Control panel; on large machines, next to the loading door |
| Long conveyor | Pull wire along the line, buttons at the feed and discharge ends |
| Robot cell | Outside the cell door, on the teach pendant |
| Open roll mill | Device that can also be activated with the body, accessible from both sides |
Reset and restart rules
After the emergency stop button has been pressed, restarting the machine should require two separate steps:
- Releasing the button latch: The button is turned or pulled. This step does not start the machine.
- Deliberate restart: A separate reset and then a start command are given.
If the machine starts by itself as soon as the button latch is released, this is a serious defect contrary to both the Work Equipment Regulation and machinery safety rules, and the machine must not be used.
Who resets? The rule is simple: no reset until it is understood why the button was pressed. The hazard that led to the button being pressed must be removed, a trapped limb or part must be safely freed and, if necessary, the energy must be locked out. The department manager or an authorised person confirms this.
How the stop is carried out also matters. The electrical equipment standard TS EN 60204-1 provides for the emergency stop to work as stop category 0 (immediate removal of power) or category 1 (controlled stop followed by removal of power). Which one is suitable is decided by the manufacturer on the basis of the machine's risk assessment; on equipment holding a heavy load or rotating under inertia, immediate removal of power can create an additional hazard.
In the operator's induction training, the operator is expected to demonstrate four things personally at the machine: the location of the emergency stop device at their own station and of the second nearest one, how the machine stops when the button is pressed, how the button latch is released and whom to inform before resetting. A new operator should not be left alone at the machine without knowing these four steps. When a line or machine is moved, the new button locations are shown to the team again.
Emergency stop testing: how and how often?
The legislation sets no fixed test frequency for emergency stops. The frequency is set according to the manufacturer's instructions and the risk assessment. A common arrangement in practice is a function test at the start of each shift or weekly on hazardous machines, with a detailed check by an authorised person at the annual periodic inspection. Under Annex III of the Work Equipment Regulation, presses and machine tools such as lathes, milling machines and machining centres undergo periodic inspection at least once a year unless the standard sets a shorter period; safety functions are also assessed in this inspection. For details see our periodic inspection page.
The emergency stop test carried out by the operator runs as follows:
| Step | Expected result | Decision on non-conformity |
|---|---|---|
| The button is pressed while the machine runs in a safe mode | The hazardous movement stops immediately or in a controlled way | The machine is not used and is reported to maintenance |
| A start command is given while the button is pressed | The machine does not start | The machine is not used |
| The button latch is released | The machine does not start by itself | Serious defect; the machine is not used |
| A reset and start command are given | The machine runs normally | Reported to maintenance |
| The result is recorded | Date, machine, tester, result | If there is no record, the test is treated as not done |
On pull-wire systems, test from different points along the line in rotation; check that the stop also works when the wire is pulled from the middle. Test results should be collected by department, and recurring faults on the same machine should be entered in the risk assessment.
The drawbacks of using the e-stop instead of a normal stop
In some businesses, operators stop the machine with the e-stop at the end of the shift or at every part change. This habit is harmful for several reasons:
- Mechanical strain: Sudden removal of power can cause shocks in dies, tools and drive components, and the workpiece and die can be damaged.
- Equipment wear: Components of the emergency stop circuit wear with frequent use; the risk of them not working when really needed increases.
- Desensitisation: A button pressed every day is no longer seen as an "emergency"; the team stops investigating the reason after an emergency stop.
- False confidence: Most importantly, an emergency stop is not energy isolation. A machine with its button pressed may retain hydraulic pressure, spring tension, parts under gravity or another supply; someone else can release the button and restart the machine.
On older machines with no emergency stop at all, or with one far from the operator, this deficiency usually ranks among the top items in the risk assessment; you can find solutions in our article on bringing old machines without CE marking into compliance. For a holistic approach to machine safety together with guards, see our article on machine guards, and for sector-specific risks our metal and machinery page. Inspecting the emergency stop arrangement on site and setting up test records is part of our OHS specialist services.
Frequently Asked Questions
Is an emergency stop button mandatory on every machine?
The Work Equipment Regulation requires an emergency stop system if the hazards of the equipment and its normal stopping time make it necessary. Machinery safety rules also require an emergency stop device except where it would not reduce the risk and on hand-held and hand-guided machines. Whether a machine needs one is decided through the risk assessment.
What colour should an e-stop button be?
Under TS EN ISO 13850, the actuator is red and the background behind it is yellow. These colours are used only for emergency stops and not on other buttons.
How often should the emergency stop button be tested?
The legislation sets no fixed frequency; the manufacturer's instructions and the risk assessment are the basis. A function test at the start of each shift or weekly is common practice on hazardous machines. At the annual periodic inspection, the authorised person also assesses it.
What should be done if the machine starts when the button latch is released?
The machine is taken out of use immediately. Releasing the latch should only permit restarting and must not start the machine. The machine is not used again until the defect has been corrected and tested.
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Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.