OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 9 Fall Protection

Section 161 Control zones

The use of a control zone is an approach to fall protection that places special requirements on workers and work being performed on a nearly level working surface within 2 metres of an unguarded edge from which a worker could fall. Control zones can be used on surfaces having a slope of up to 4 degrees measured from the horizontal.

If a worker works within 2 metres of the control zone i.e. within 4 metres of the unguarded edge, a raised warning ling or equally effective means is required. If a worker works within the control zone, then a travel restraint system must be used.

A control zone cannot be used if the level working surface on which work is being performed is less than 4 metres wide. In such circumstances, one of the other methods of fall protection required by the OHS Code must be used.

Work away from unguarded edge

Situations may arise where, on a large flat roof for example, work is performed at a significant distance away from an unguarded edge e.g. at a penthouse near the centre of the roof. With the exception of when workers enter or leave the work area at an unguarded edge, workers have no contact with the edge. Upon accessing the roof, workers must proceed directly to their work area. Under such circumstances, a line defining a control zone is unnecessary, as are the remaining requirements for fall protection that would normally apply at the unguarded edge.

Line defining the control zone

If a worker works within 2 metres of the control zone i.e. within 4 metres of the unguarded edge, a raised warning line or equally effective means of alerting the worker to the unguarded edge is required (see Figure 9.25). The raised warning line or other equally effective means such as barricades must be placed at least 2 metres from the edge. The warning method provides a visual and physical reminder of the presence of the hazard.

Figure 9.25 Example of control zone marked out on flat roof

For compliance purposes, a raised warning line can consist of ropes, wires or chains, and supporting stanchions, and should be

(a) flagged or marked with highly visible materials at intervals that do not exceed 2 metres (6.5 feet),

(b) rigged and supported so that the lowest point (including sag) is not less than 0.9 metres (34 inches) from the walking or working surface and its highest point is not more than 1.2 metres (45 inches) from the walking or working surface,

(c) attached to each stanchion in such a way that pulling on one section of the line between stanchions will not result in slack being taken up in the adjacent section before the stanchion tips over, and

(d) the rope, wire or chain must have a minimum tensile strength of 2.2 kN (500 lbs).

An “equally effective method” might be a substantial barrier e.g. pile of materials or supplies, tall parapet, building system pipes and ducts, etc. that is positioned between the worker and the unguarded edge, preventing the worker from getting to the edge. Since this substantial barrier is acting as a guardrail, it must at all time be at least 920 millimetres (36 inches) tall while the protected worker is using it.

Work within the control zone

If a worker works within the control zone, then a travel restraint system or equally effective means that prevents the worker from getting to the unguarded edge must be used. A travel restraint system is always preferred but may not be appropriate or possible in all circumstances.

An “equally effective method” might be a substantial barrier e.g. pile of materials or supplies, tall parapet, building system pipes and ducts, etc. that is positioned between the worker and the unguarded edge, preventing the worker from getting to the edge. Since this substantial barrier is acting as a guardrail, it must at all time be at least 920 millimetres (36 inches) tall while the protected worker is using it.

A control zone cannot be used if the level working surface on which work is being performed is less than 4 metres wide. In such circumstances, one of the other methods of fall protection required by the OHS Code must be used.

For more information

Ellis, NJ. Introduction to Fall Protection, 2nd edition. American Society of Safety Engineers, Des Plaines, Il; 1993.