A worker strapped into a harness and secured by a lanyard to a roof anchor looks safe. But the difference between falling off the roof or not – and providing level three controls under the fall prevention hierarchy – comes down to subtle differences in the design and use of the equipment. Here, safe work at heights specialist, Carl Sachs of Workplace Access & Safety in Australia explains why the distinction between level three fall restraint and level four fall arrest systems is important and how workplace controllers can be sure systems are designed for safety and compliance.

The equipment used in level three and four controls is identical – harnesses, lanyards, and static lines or roof anchors – but the outcomes are very different. Level three controls called “work positioning systems” or “fall restraint systems” prevent users getting close enough to an edge where they could fall. In contrast, the less protective level four “fall arrest systems” simply limit the distance the user can fall.

The implications are potentially tragic. Falling even a short distance from a roof can lead to very serious injuries caused by the pendulum effect or suspension trauma. Described in the codes of practice for fall prevention, the pendulum effect occurs when a person falling over the edge swings like a pendulum and slams into the side of the building or hits the ground.

Hitting the ground while wearing a harness, shock absorber, and lanyard is a real possibility when falling from a single storey building. Refer to AS/NZS 1891 for more detailed calculations.

Suspension trauma, on the other hand, can be lethal at any height. In a mine safety alert, the NSW Department of Primary Industries warned: “Suspension trauma or orthostatic intolerance results from a harness restricting blood flow from the legs. Harness restriction leads to pooling of blood in the legs which reduces the return blood flow to the heart. The brain, kidneys, and other organs are then deprived of blood and oxygen which leads to a lack of consciousness, serious injury, and then death. A lack of consciousness can occur after five minutes.”

The alert also warns that rescuers must not only be prompt but well trained.

“Rescue must be carried out very carefully or it can also cause death. Moving a person quickly into a horizontal position – a natural reaction – is likely to cause a large volume of deoxygenated blood to move to the heart if a person has been suspended for an extended period. The heart may be unable to cope with the abrupt increase in blood flow, causing cardiac arrest.”

Planning level three and level four
The best approach is to avoid falls altogether by implementing level one, two, or three controls. In practical terms, the difference between fall restraint and fall arrest can be as simple as the location of the anchor points and the length of the lanyards.

The best way to determine whether a system is level three or four is to check the layout. When users need to reach a corner of the building to maintain downpipes, for example, the rope is extended and they can fall over the edge. This makes the system a level four fall arrest system rather than a level three fall restraint system.

A fall restraint system includes extra anchorage points called diversion anchors. This time, to get to the downpipe, users hook onto the diversion anchor from the centre anchor and then work in a smaller radius, maintaining restraint. Fall restraint or work positioning systems can have three or even four times as many anchors as a fall arrest system. Of course, if the user chooses not to employ the diversion anchors, even the best designed level three fall restraint system operates as a level four fall arrest system.
The answers
Follow the hierarchy of controls. There are many situations where the hazard can be eliminated altogether by redesigning the work (for example, work from a scissor lift or platform). If that isn’t practicable, use passive fall prevention devices – like guard rails and walkways – that don’t require a high level of user skill.

If level three controls must be used, ensure the system is properly designed, maintained, and inspected and tested annually (or every six months in South Australia) in accordance with legislation. Equally importantly, train all users and put permit systems and inductions in place. And, because falls do happen, have a well-rehearsed rescue plan and keep a second person on stand-by to carry it out.
For more information contact: Workplace Access & Safety,
visit: www.workplaceaccess.com.au