Free fall clearance: how much height does a fall line really need?

According to the Dutch Working Conditions Decree, there is a fall hazard at heights of 2.5 metres or more. However, a fall arrest line at this height is not automatically the solution. A fall arrest line does not stop you immediately: you fall first, and then the energy absorber opens. With the Petzl ABSORBICA-Y MGO 80, your feet will drop by the maximum permitted fall distance of 2.58 metres. At 2.5 metres, you will hit the ground. That is why Petzl requires 3.58 metres of clearance.

How much free fall clearance do you need?

Free fall clearance (referred to in manuals as tirant d'air or clearance) is the space that must be clear beneath you so that you do not hit anything in the event of a fall. It does not have to be the ground: a pipe, machine or lower floor also counts. In the ABSORBICA-Y MGO user manual, Petzl calculates based on the maximum permitted fall: the anchor point is one line length below your harness point. With the MGO 80, this is approximately 50 cm above your feet, and with the MGO 150, approximately 33 cm below.

	MGO 80	MGO 150
Total line length	1.00 m	1.83 m
Maximum free fall	2.00 m	3.66 m
Absorber opens, up to 100 kg	0.58 m	0.91 m
Absorber opens, 100 to 140 kg	0.87 m	1.40 m
Clearance beneath your feet, up to 100 kg	3.58 m	5.57 m
Clearance beneath your feet, 100 to 140 kg	3.87 m	6.06 m
Minimum anchor point height, up to 100 kg	4.08 m	5.24 m
Minimum anchor point height, 100 to 140 kg	4.37 m	5.73 m

These values apply only to the ABSORBICA-Y MGO for a weight of 60 to 140 kg including tools. The EN 355 label states a maximum elongation of 0.9 m (MGO 80) and 1.61 m (MGO 150). Other fall arrest lines have their own values, which are stated in their own user manual.

How to calculate it yourself

At the maximum permitted fall, the free fall is twice the line length. Petzl then adds the absorber opening and a 1-metre safety margin:

2.00 m free fall + 0.58 m absorber + 1.00 m margin = 3.58 m beneath your feet

For the anchor point height, add the line length, the absorber, 1.5 metres between the harness point and your feet and the same margin: 1.00 + 0.58 + 1.50 + 1.00 = 4.08 metres. Never estimate the absorber value yourself. It depends on the fall and your weight and is only known by the manufacturer.

Four things you might not expect

• The number in the name is not the length. The MGO 80 is 1.00 metre long in total, the MGO 150 is 1.83 metres. So do not use the 80 or 150 from the product name in your calculations.
• The 100 kg includes tools and clothing. If you weigh 90 kg and carry 15 kg of equipment, you fall into the heavier column. This adds 29 cm for the MGO 80 and 49 cm for the MGO 150. If you are between two values, use the higher one.
• A separate line attached to your harness limits the absorber. If you attach the free arm of a Y-line to your harness, the absorber may not open as far. Only use special parking points that release the MGO hook in the event of a fall. With the Petzl Newton harnesses, Petzl refers to this on the international version, not the European one. For the Newton, Volt and Avao ranges, a separate parking accessory is also available.
• A flexible line stretches. If you are attached to a flexible horizontal anchor line (EN 795 type C), the stretch of that line is added on top. You will find this in the anchor line manual.

Not enough space? Here are your options

1. Choose a higher anchor point. According to Petzl, this is the easiest way. The higher the anchor point, the shorter the fall and the less the absorber opens. The table above applies to the maximum permitted fall.
2. Choose a shorter line. If you need to work above your anchor point, keep the line as short as possible. The adjustable ABSORBICA-I VARIO, for example, can help.
3. Prevent yourself from falling. With fall restraint, you cannot reach the edge. Such a system does not arrest a fall, so the line must be short enough to prevent you from reaching the edge.
4. Choose a different system. A fall arrester has its own clearance value. Compare it in the user manual before choosing.

If it can be done without a harness, then that is the preferred option. The Dutch Working Conditions Decree prioritises a safe working floor or guardrail and only then personal fall protection.

Be aware of edges and rescue

A fall over an edge is a separate case. Only the ABSORBICA-Y MGO 150 has been tested for this (PPE-R/11.074_V3), over a steel edge with a radius of 0.5 mm and no burrs. The MGO 80 does not have this marking. If the MGO 150 is used on a platform where there is a risk, there must be at least 6.1 metres between the anchor point and the ground. Also stay within 1.5 metres horizontally of the anchor point to limit swinging. If the edge is sharper or has burrs, exclude a fall over that edge or install edge protection.

Furthermore, a successful arrest is not the end. Hanging unconscious in a harness is life-threatening. Therefore, ensure there is a rescue plan and the means to carry it out immediately before anyone goes up.

Frequently asked questions

What is free fall clearance?

The minimum space beneath the user that must be clear so that you do not hit an obstacle in the event of a fall. This includes the fall, the opening of the absorber and a safety margin.

Does fall protection also apply below 2.5 metres?

Yes, if there is an increased fall risk, such as working over water, on roads or near overhanging parts. Include fall hazards at every height in your RI&E.

Can I use Petzl's values for another brand?

No. Absorbers and line lengths differ by product, so always use the user manual for your line. For ABSORBICA lines, you can also use the Petzl clearance calculator.

Are you unsure about your situation?

View all fall arrest lines and energy absorbers or harnesses. Feel free to send us your anchor height, the clearance and your weight including tools, and we will help you.

Sources: Petzl ABSORBICA-Y MGO user manual (L0047200C), Petzl Tech Tip on clearance with ABSORBICA-I and Y, Petzl 2026 catalogue, Dutch Working Conditions Decree Article 3.16 and Arboportaal. Images: Petzl and own diagram. Last checked on November 6, 2026. This article does not replace the user manual or the risk assessment of your workplace.