OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 9 Fall Protection

Section 156 Boom-supported work platforms and aerial devices

Subsection 156(1) Boom-supported work platforms

Experiences at Alberta workplaces involving ejections has resulted in this subsection explicitly requiring that workers use a personal fall arrest system when working from a boom-supported elevating work platform, boom-supported aerial device or forklift truck work platform e.g. telescopic fork handler (see Figures 9.19 and 9.20). Since ejections can happen at any height, particularly when the boom is in its stowed condition and the unit is moving or being loaded or unloaded off a trailer, the requirements apply even though the worker’s position above grade may be less than 3 metres in height.

Figure 9.19 Example of an articulated boom-supported aerial device (insulated or non-insulated)

Figure 9.20 Example of a hybrid aerial device – articulated aerial device with extendible (telescopic) boom

To reduce the likelihood of a worker being ejected from the work platform, the worker’s personal fall arrest system must be connected to an anchor point. If the work platform manufacturer does not provide an anchor point (usually because the unit is very old), then an anchor point certified by a professional engineer must be used. While this could mean having to add an engineered “hard” anchor point to the boom, anchor slings designed for use with booms are also available. If such an anchor sling is used, a professional engineer is still required to specify the limits under which that anchor sling can be safely used without affecting the stability of the machine.

The worker’s lanyard, if reasonably practicable, needs to be short enough to prevent the worker from being ejected yet be long enough to allow the worker to perform his or her work. Work platforms come in square and rectangular shapes. Because of the physical shape of the work platform, the location of the anchor points, and the need for workers to be able to move about the entire platform, it may be impossible to both limit the length of the lanyard and still allow a worker to perform his or her work unimpeded. The result may be a compromise.

The required personal fall arrest system, which must include a shock absorber as required by subsection 142.3(2), can function as a travel restraint system preventing the worker from being ejected. However, if the lanyard is too long to prevent ejection, then the shock absorber will help limit arrest forces on both the worker and the platform’s anchor point in the event of an ejection and fall.

The referenced CSA Standard Z259.16-04, Design of Active Fall-Protection Systems, specifies requirements for the design and performance of complete active fall protection systems. It is intended for professional engineers with expertise in designing fall protection systems.

Subsections 156(2) and 156(3) Scissor lifts and similar work platforms

Almost all modern scissor lifts (see Figure 9.21) are equipped with anchor points. Some manufacturers recommend that a travel restraint system (consisting of a full body harness and lanyard) or a personal fall arrest system be used by workers on the scissor lift, connected to the anchor points provided. Other manufacturers recognize that when a scissor lift is correctly set up and sited, guardrails offer appropriate work protection.

Figure 9.21 Examples of scissor lifts and a similar vertical aerial platform

Some older model scissor lifts may not be equipped with anchor points. These units will very likely, in their manufacturer specifications, indicate that the unit’s guardrails provide worker fall protection. Subsection (3) then applies.

Subsections (2) and (3) must be read together. Subsection (3) overrides the travel restraint system requirement of subsection (2) by recognizing that the scissor lift manufacturer may allow the worker to work from the work platform and rely on the guardrails to provide protection against falling. The manufacturer’s instructions for use must state that the use of the scissor lift’s guardrails as a means of fall protection is acceptable. Workplace Health and Safety agrees with this assessment.

This approach has several benefits:

(a) it defaults to the use of a full body harness and lanyard for travel restraint, which can only be overridden by the manufacturer;

(b) it reflects what may be a future trend in the aerial work platform industry without conflicting with that trend;

(c) from a compliance perspective, any worker on a scissor lift should be using a full body harness and lanyard connected to an anchor point. If the worker is not, then the employer can be requested to produce a copy of the manufacturer’s operating manual and show where in the manual the manufacturer allows guardrails alone to be used. This ensures that manuals are available and initial compliance is a simple visual check to confirm that a harness and lanyard are being used; and

(d) despite warnings to the contrary, workers continue to stand on midrails (and toprails) to complete work tasks. If a worker is wearing a correctly selected and adjusted travel restraint system, there is less chance that he or she will be able to stand on the rails. As a rule of thumb, if a worker can stand on the midrail while using the travel restraint system, then he or she can fall off the platform.

Scissor lifts and similar vertical aerial platforms are generally more stable than a work platform supported by a boom. Reflecting this higher level of safety, a worker need not use a full body harness and lanyard connected to an anchor point if the scissor lift or similar vertical aerial platform is operated on a firm, substantially level surface with all of the manufacturer’s guardrails and chains in place. However, if the manufacturer’s specifications require the use of a travel restraint or fall arrest system when the vertical aerial platform is being used, then the manufacturer’s specifications take precedence and must be followed.

Research studies

In a 2007 study of aerial lift fatalities in the U.S. for the period 1992–2003, there were 306 deaths – 228 involving boom lifts and 78 involving scissor lifts. Table 9.2 summarizes these deaths by manner of fall and the activity being performed at the time of the event.

Table 9.2 Aerial lift deaths by manner of fall and activity, 1992–2003


Fall From




Boom Lifts

Construction and repairing





Logging, trimming and pruning





Vehicular and transportation operations





Other activities





Boom Lift Total





Scissor Lifts

Construction and repairing





Vehicular and transportation operations





Painting and cleaning





Other activities





Scissor Lift Total





Source: U.S. Bureau of Labor Statistics Census of Fatal Occupational Injuries (CFO) Research File.

As shown in Table 9.2, tipovers/collapses were involved in 46 percent of the fall deaths associated with boom lifts and 56 percent of fall deaths associated with scissor lifts. Failure to use a harness or belt and lanyard to tie off while performing tasks was reported in 42 of the 228 (18 percent) boom lift fatalities. In 25 deaths involving 23 boom lift ejection or tipover/collapse events, the lift was struck by a vehicle, train or crane. In nine boom lift ejections the worker or lift was struck by a falling tree. Other contributing causes to boom lift deaths included open platform doors or defective latches.

Major contributing factors for scissor lift falls included surface conditions and scissor lift motion. In six tipover events (14 percent of 44 scissor lift tipovers), uneven or sloped ground or driving on/off a flatbed truck was a factor, and in seven tipover events (16 percent) driving into holes or over a sidewalk or similar edge was a factor.

Results from this study indicated that for a significant percentage (82 percent of falls involving a different fatality database) of incidents involving a fall from height, existing fall prevention systems such as guardrails, chains, gates/doors, belts, and harnesses with or without lanyards were not being used at the time of the incident.


Pan CS, Hoskin A, McCann M, Lin ML, Fearn K, Keane P. Aerial lift fall injuries: A surveillance and evaluation approach for targeting prevention activities. Journal of safety research 2007; 38(6): 617-25.

In a different study of deaths involving aerial work platforms used in the U.S. construction industry between 1992 and 1999, it was determined that boom-suspended work platforms accounted for almost 70 percent of deaths involving aerial work platforms. The study reported that

(a) half of all falls from boom-supported work platforms involved being ejected from the bucket or platform after being struck by vehicles, cranes, or crane loads, or by falling objects, or when the work platform suddenly jerked, and

(b) two-thirds of the deaths from tipovers/collapses of boom-supported work platforms occurred when the bucket cable or boom broke or the bucket fell. Almost one-third of the deaths were due to tipovers.

This same study found that scissor lifts accounted for over 25 percent of the aerial lift deaths. The study reported that

(a) the causes of scissor lift falls were unknown for over half of the fall deaths,
(b) in one-fifth of the falls, the worker was ejected from the scissor lift, mostly when an object struck the scissor lift. The rest of the fall deaths occurred after removal of chains or guardrails, or while standing on or leaning over railings,
(c) three-quarters of the tipovers of scissor lifts resulted in fall deaths. For the rest, workers died from being struck by the falling scissor lift, and
(d) about two-fifths of the tipovers occurred when the scissor lift was extended more than 5.5 metres (15 feet), mostly while driving the lift.

For more information

Deaths from Aerial Lifts.
The Centre to Protect Worker’s Rights, 2001

Subsection 156(4) Movement not adequately restricted

In some cases, the travel restraint system used on a scissor lift or elevating platform with similar characteristics cannot adequately restrict a worker’s movement in all directions, perhaps because of its rectangular shape. If this is the case, then a personal fall arrest system must be used.

The required personal fall arrest system must include a shock absorber as required by subsection 142.3(2). If a worker does fall off the platform then the shock absorber will help limit arrest forces on both the worker and the platform’s anchor point.