What Actually Happens When a Fall Arrest Lanyard Deploys

Most people who manage buildings where tradespeople access the roof have never seen a fall arrest lanyard deploy. If you have ever assumed the system would just work, that assumption is worth examining carefully before someone puts it to the test.

A fall arrest lanyard is designed to stop a person from hitting the ground. But the mechanics of how it does that are more involved than most building owners realise, and those mechanics have a direct bearing on how a height safety system needs to be designed and installed. A lanyard that meets the standard is not the same as a system that will actually save someone in your specific building.

The starting point is understanding fall factor. Fall factor is the distance a worker falls divided by the total length of rope available in the system to absorb that energy. It is a way of measuring how violent the arrest will be. A fall factor of 1 means the worker fell a distance equal to the rope length. A fall factor of 2 is the worst possible scenario, and it occurs when the anchor point is at the same level as, or below, the worker’s attachment point on their harness. In that situation, the worker falls twice the length of the rope before the system catches them. On a rooftop, this can happen when a worker clips to a low anchor and then steps up to a higher level before a fall occurs. The anchor being below the worker at the moment of the fall is what creates the Factor 2 condition.

A general fall, which is the more common real-world scenario, involves a fall factor below 2. This is sometimes called a sub-factor 2 fall. The anchor is positioned above the worker’s attachment point, which is how a properly designed system should always work. In a typical general fall, the worker might free-fall somewhere between half a metre and one metre before the lanyard comes taut. That is still enough to cause serious injury without the right equipment, and it is enough to activate the energy absorber.

This is where the numbers matter. The energy absorber, sometimes called a shock absorber, is the tear-through pack built into the lanyard. It extends as it absorbs the energy of the arrest, keeping the force on the body below the 6kN maximum required by AS/NZS 1891.1. But as it extends, it adds to the total distance the worker travels. In a general fall with a fall factor between 0.5 and 1, a standard energy absorber will typically extend somewhere between 400 millimetres and 900 millimetres, depending on the worker’s weight, the specific fall factor, and the product. In a Factor 2 fall, the energy absorber may extend to its full length of 1.2 to 1.75 metres.

Add that extension to the initial free fall, the full length of the lanyard, and the movement of the harness on the body, and the worker can end up 3 to 4 metres below their starting position even in a general fall. A 2-metre lanyard does not mean a 2-metre fall. That misunderstanding is one of the most common problems we see in poorly designed systems, and it is why clearance below the worker is not a secondary consideration. Clearance is a core part of system design.

At Anchored Height Safety, we see the consequences of this misunderstanding regularly. Building owners and tradespeople assume that compliant equipment equals a safe system. It does not, unless the anchor points are in the right positions for your specific roof. We design and install height safety systems that account for total fall distance, not just lanyard length, because that is what the Australian Standards require and what actually protects people.

When we assess your roof, we look at the full picture. We evaluate anchor point placement to ensure the anchor is always above the worker’s attachment point wherever possible. We assess the clearance to the next level, to the roof edge, and to any obstacles below. We specify the right combination of anchor points, horizontal lifelines, and connecting equipment for your building’s layout. Our industry-leading documentation tells your trades exactly what equipment is installed, what each component is rated for, and when it was last inspected, so they arrive knowing the system and can work with confidence.

When your height safety system is designed correctly for your building, your trades get on the roof, do their job, and get home. Compliance documentation is current, your insurer has evidence of due diligence, and there is nothing left to chance.

When the system is wrong, a general fall that should have been survivable becomes something far worse. The energy absorber deploys, the worker swings into a parapet or drops past a lower level, and the investigation that follows will ask who was responsible for the safety system on that roof. That question will land with you.

If you are not sure whether your height safety system accounts for total fall distance and clearance, call us on 03 9555 3586, email us at sales@anchored.com.au or visit anchored.com.au. We will assess your roof and give you a clear picture of where you stand.