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This page explains the international safety distances principles. Our EN ISO 13857 guide covers the European reference checks, project interfaces and supply brief for an EU machine.
EN ISO 13857: European project guidanceISO 13857: guard heights, openings and safety distances
Modular machine guarding and perimeter fencing designed around ISO 13857 principles to help prevent people reaching hazardous areas over, under, around or through guards.
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From ISO 13857 to your guarding brief
Include a dimensioned plan, hazard locations, proposed heights and openings, floor conditions and access points. Mark any dimensions still awaiting engineering confirmation.
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Understanding the standard
What is ISO 13857?
ISO 13857:2019 is the international machinery safety standard that establishes safety-distance values intended to prevent people reaching hazardous zones with their upper and lower limbs.
For machine guarding projects, ISO 13857 is commonly used to assess how a person could reach a hazard:
• Over the top of a perimeter guard;
• Through mesh, slots or other openings;
• Under a guard panel;
• Around the side or end of a guard;
• Through conveyor, product-transfer or service openings; and
• Into a crushing, shearing, drawing-in or entanglement zone.
The standard is especially relevant when selecting guard height, mesh aperture, floor clearance and the distance between the guard and hazardous movement. It does not provide a single universally safe fence height or mesh size. Those dimensions must be assessed against the specific hazard location, opening geometry and possible reach direction.
ISO 13857 does not operate in isolation. Machinery risk assessment and risk reduction are generally addressed through ISO 12100. Guard design and construction are addressed by ISO 14120, while interlocking devices and measures to reduce foreseeable defeat are covered by ISO 14119. Where the position of a protective device depends on approach speed and machine stopping time, ISO 13855 may also be relevant.
For machine guarding projects, ISO 13857 is commonly used to assess how a person could reach a hazard:
• Over the top of a perimeter guard;
• Through mesh, slots or other openings;
• Under a guard panel;
• Around the side or end of a guard;
• Through conveyor, product-transfer or service openings; and
• Into a crushing, shearing, drawing-in or entanglement zone.
The standard is especially relevant when selecting guard height, mesh aperture, floor clearance and the distance between the guard and hazardous movement. It does not provide a single universally safe fence height or mesh size. Those dimensions must be assessed against the specific hazard location, opening geometry and possible reach direction.
ISO 13857 does not operate in isolation. Machinery risk assessment and risk reduction are generally addressed through ISO 12100. Guard design and construction are addressed by ISO 14120, while interlocking devices and measures to reduce foreseeable defeat are covered by ISO 14119. Where the position of a protective device depends on approach speed and machine stopping time, ISO 13855 may also be relevant.
Identify the hazardous zone
Identify all locations where a person could be injured by moving parts, including crush points, nip points, rotating components, robot movement, tooling, conveyors and ejected material.
Assess possible reach paths
Consider whether a person could reach over, under, around or through the proposed guard, including through mesh apertures, gaps at corners, conveyor openings and clearances beneath panels.
Select guard dimensions
Determine guard height, aperture size, floor clearance and guard-to-hazard distance together. Changing one dimension can affect the safety distance required for the others.
Verify the installed layout
Confirm the actual installation matches the approved design. Measure heights, gaps, openings and distances after installation, particularly around gates, columns, conveyors and existing equipment.
Why Safety Distances Matter
How is ISO 13857 used in machine guarding design?
ISO 13857 provides safety-distance guidance, but it is not a substitute for a machine risk assessment. The guarding designer must first understand the hazard, the location of hazardous movement, foreseeable access and the machine’s operating conditions.
The standard is then used to assess whether the physical layout prevents a person reaching the hazard.
The standard is then used to assess whether the physical layout prevents a person reaching the hazard.
A person could reach over the guard
Guard height, hazard height and the horizontal distance between the guard and hazard must be considered together. A taller guard may reduce reach-over access, but only where the arrangement prevents a person from leaning or reaching into the hazard zone.
A person could reach through mesh or an opening
Mesh aperture and setback distance must be assessed together. A larger opening can allow a finger, hand or arm to extend further through the guard, requiring the hazard to be positioned further away.
A person could reach beneath a guard
Floor clearance must be controlled where lower-limb or upper-limb access beneath the guard could expose a person to the hazard. Uneven floors, ramps, pits and raised machine bases can affect the actual clearance.
A person could reach around a guard edge
Guard ends, wall interfaces, columns, service penetrations and conveyor transfer points require the same attention as the main fence line. A compliant panel arrangement can be undermined by an uncontrolled side gap.
The hazard is inside a large automated cell
Perimeter guarding should be positioned to prevent reach-through and reach-over access while maintaining sufficient separation from hazardous robot movement, conveyors, palletisers, tooling and other equipment in accordance with the risk assessment and applicable machinery or robot safety standards.
Access is required through a gate or door
Safety distance alone may not be sufficient. Where opening a movable guard provides access to hazardous movement, interlocking, guard locking, restart prevention and safety-control performance may need to be considered.
The process requires material transfer openings
Pallet, product or conveyor openings should be designed so that materials can pass through without allowing people to access the hazardous area. Tunnel guards, fixed side protection, interlocked gates or protective devices may be required depending on the application.
Why Guarding Matters
Designing machine guarding around ISO 13857
A guarding layout should prevent hazardous access without creating unnecessary operational problems. The most reliable solution is usually one that controls access at the source while allowing operators and maintenance personnel to complete legitimate tasks safely.
Guard height and hazard position
Guard height cannot be selected from a catalogue alone. The height of the hazardous area, the position of the guard and the opportunity to reach over the top must all be assessed together.
Mesh aperture and setback distance
A small mesh opening does not automatically make a guard suitable. The hazard must remain far enough behind the guard that a person cannot reach it through the opening.
Floor clearance and uneven surfaces
The clearance beneath a machine guard should be assessed against possible access by feet, legs, hands or arms. Site conditions such as sloping slabs, pits, drainage channels and cable trenches may create larger gaps than shown on the drawing.
Conveyor and product openings
Conveyor entry and exit points are common sources of uncontrolled access. Guarding must account for the movement of products, pallets and materials without leaving a route to hazardous rollers, transfer points or automated equipment.
Gates and controlled entry
Gates should be located where people genuinely need access for loading, fault recovery, cleaning and maintenance. Where entry exposes personnel to hazardous movement, the gate and associated safety controls should be designed as part of the complete safeguarding system.
Existing machinery and retrofit projects
Retrofitted guarding often has to work around machine frames, conveyors, control cabinets, building columns and existing services. Measurements should be verified on site before manufacture. Small changes to guard position, mesh type or floor clearance can affect reach-prevention performance.
Common ISO 13857 Machine Guarding Mistakes
Common safety-distance issues include:
- Selecting mesh based on appearance rather than aperture and hazard setback;
- Positioning a guard too close to a robot, conveyor, rotating component or pinch point;
- Assuming a standard fence height is appropriate for every machine;
- Leaving large gaps beneath panels because of uneven floors or poor installation;
- Ignoring reach-around access at guard ends, columns and wall interfaces;
- Allowing uncontrolled access through conveyor or material-transfer openings;
- Installing a gate without considering interlocking or restart prevention;
- Changing a guard layout on site without reassessing the safety distance; and
- Treating the physical guard separately from the machine’s controls and operating procedures.
A modular fencing system can provide a practical guarding structure, but conformity with applicable safeguarding requirements depends on the completed layout, openings, access arrangements and machine interface.
Connect distance to the complete system
Use ISO 13857 with guard design, interlocking and stopping behaviour
Reach-prevention dimensions are one part of the safeguarding decision. The physical guard, access strategy and any safety-related controls still need to be coordinated.
ISO 12100
Defines the risk-assessment process that determines where distance can provide adequate risk reduction and where more is needed.
Risk-assessment guideISO 14120
Addresses the construction and selection of the guard whose height, openings, rigidity and position maintain the protective boundary.
Guard design guideISO 14119:2024
Addresses interlocking devices used at movable guards and measures intended to reduce foreseeable defeat.
Interlocking guideISO 13855:2024
Addresses a different distance question: positioning safeguards in relation to approach and stopping performance.
Safeguard-positioning guideISO standards hub
Compare the core machinery-safety standards by scope and project decision.
Explore the ISO standards hubFrequently Asked Questions About ISO 13857 (FAQ)
ISO 13857 is an international machinery safety standard that provides safety-distance values intended to prevent hazardous areas being reached by upper and lower limbs.
Yes. ISO 13857 is commonly used when assessing mesh apertures and other guard openings. The opening size and distance from the opening to the hazard must be considered together.
No. There is no single guard height suitable for every application. The required height depends on the location and height of the hazard, the guard position and the potential for a person to reach over the top.
The required distance depends on the type and size of the opening, the direction of possible reach and the location of the hazard. ISO 13857 provides safety-distance values that should be applied to the specific arrangement.
Yes. A guard positioned too close to hazardous movement may allow a person to reach through, over, under or around it. The guard-to-hazard distance must be assessed with the aperture size and other access routes in mind.
Yes. Floor clearance and other lower openings should be assessed where a person may be able to reach a hazardous area with their feet, legs, hands or arms.
ISO 13857 addresses reach-prevention distances. Interlocking devices associated with movable guards are more specifically addressed in ISO 14119. The complete safeguarding arrangement may also require safety-related control-system design.
ISO 13857 provides safety-distance values intended to prevent people reaching hazardous zones. ISO 14120 covers the general design and construction requirements for fixed and movable guards.
Not by itself. ISO 13857 is primarily concerned with reach prevention. Where the position of a protective device depends on approach speed and machine stopping time, ISO 13855 and relevant safety-control requirements may also apply. ISO 13857 does not itself calculate machine stopping distance.
Yes. ISO 13857 is commonly used when assessing retrofit guards around existing machinery. The upgrade should also consider the overall machine risk assessment, actual site dimensions, access requirements, stopping performance and applicable local legal requirements.
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