Fall protection – buyer guide
How to Calculate Fall Clearance: EN 355 Guide
How to calculate the clearance a fall arrest system needs before anyone works at height.
Short answer: required fall clearance is the sum of lanyard length, energy absorber deployment, worker height below the attachment point, and a safety margin. For a 2 m EN 355 lanyard the working figure is commonly around 6.5 m below the anchor: 2 m lanyard, up to 1.75 m absorber extension, roughly 1.5 m of body length, plus 1 m clearance. If less than that is available, an energy-absorbing lanyard is the wrong equipment and a retractable device to EN 360 should be used instead.
Why Clearance Is the Calculation That Gets Missed
A fall arrest system limits the force on the body to a survivable level, which EN 355 caps at 6 kN. It achieves this by allowing the energy absorber to tear open and extend, converting kinetic energy into deformation. That extension is not a defect — it is the mechanism. But it means the worker falls considerably further than the length of the lanyard.
A correctly rated harness, lanyard and anchor will still result in a ground impact if the structure does not offer enough space below. Clearance is the one element of the system that no product certification can supply; it has to be calculated for the specific workplace.
The Four Components
| Component | Typical value | Notes |
|---|---|---|
| Lanyard length | Up to 2 m | EN 355 limits the assembly, including connectors, to 2 m |
| Energy absorber deployment | Up to 1.75 m | Maximum extension permitted by EN 355 |
| Worker height below attachment | About 1.5 m | Dorsal D-ring to feet, varies with build |
| Safety margin | 1 m minimum | Prevents contact if any value is underestimated |
Adding these gives approximately 6.25 m, which is why 6.5 m is used as a practical planning figure for a full-length lanyard attached at foot level or above. Where the anchor is above head height, the required clearance decreases; the calculation must always start from the actual anchor position.
Fall Factor Changes Everything
Fall factor is the distance fallen divided by the length of lanyard available to absorb it. It determines the severity of the arrest.
- Factor 0 — anchor above the head, lanyard taut. The shortest possible fall and the lowest forces.
- Factor 1 — anchor at harness attachment height. The worker falls the length of the lanyard before arrest begins.
- Factor 2 — anchor at foot level. The worker falls twice the lanyard length. This is the maximum an EN 355 lanyard is designed to arrest, and it generates the highest forces and the greatest clearance requirement.
Anchoring as high as practicable is the single most effective way to reduce both the arrest force and the clearance needed. Where an overhead anchor is impossible, the equipment selection must account for factor 2 explicitly — not every lanyard on the market is rated for it.
When to Use a Retractable Device Instead
A self-retracting lifeline to EN 360 keeps the line under light tension and locks within a short distance, so the total fall distance is far shorter than with an energy-absorbing lanyard. Typical clearance requirements are around 2 to 3 m depending on the model, against roughly 6.5 m for a 2 m lanyard.
For work on low structures, inside vessels, on scaffolds close to the ground or on vehicle loading platforms, a retractable device is usually the only fall arrest option that fits the available space. Check the manufacturer’s stated clearance for the specific model, as it varies with device length and locking distance.
Restraint and Positioning Are Not Fall Arrest
EN 358 covers work positioning and restraint systems. A restraint system is set up so the worker physically cannot reach the fall hazard, and it is not designed to arrest a fall. A positioning belt supports the worker at a work face but likewise offers no fall arrest capability.
Where a fall is possible, an EN 361 full body harness with an EN 355 lanyard or an EN 360 retractable device is required. A positioning belt used alone in a genuine fall situation can cause severe internal injury, because the arrest load is applied to the abdomen rather than distributed through the harness.
Frequently Asked Questions
Can a fall arrest lanyard be used after a fall?
No. Once the energy absorber has deployed it has done its job and cannot do it again. The lanyard must be withdrawn from service and destroyed. The harness must also be inspected by a competent person and is normally retired, as internal webbing damage is not always visible.
What anchor strength is required?
Anchor devices certified to EN 795 are tested to defined requirements by class. Where a structural anchor point is used rather than a certified device, it must be assessed by a competent person for the loads a fall arrest can generate. Never anchor to handrails, pipework or ductwork without a structural assessment.
Why does rescue planning matter for clearance?
Arresting the fall is only half the system. A worker left suspended in a harness can develop suspension trauma within a short period, so a rescue plan and the means to execute it must be in place before work starts. Descender devices to EN 341 are commonly part of that plan. Clearance calculation and rescue planning should be done together, because both depend on the geometry of the same workplace.
Next Steps for Buyers
Measure the available clearance below each anchor position before selecting equipment, not after. Where space is tight, specify EN 360 retractable devices and confirm the model’s stated clearance. MSQ SAFE supplies EN 361 harnesses, EN 355 lanyards, EN 360 retractables and EN 795 anchor devices with full test documentation. Browse fall protection, review the standards library, or request a quote.