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Safeguard OSH Solutions - Thomson Reuters

Safeguard OSH Solutions - Thomson Reuters

Health, Safety, and ACC

2.4 Hierarchy of controls

Hierarchy of controls
The HSW Act provides that regard must be had to the principle that workers and other persons should be given the highest level of protection against harm to their health, safety and welfare from hazards and risks arising from work or from specified types of plant as is reasonably practicable. The Health and Safety at Work (General Risk and Workplace Management) Regulations 2016 (HSW (General Risk) Regulations) contain a hierarchy of controls that indicate how to implement this general principle in particular circumstances.
The hierarchy recognises that certain controls that either eliminate or reduce risk at source or provide collective protection are more effective than administrative controls or PPE in protecting the health and safety of workers and other persons and therefore must be given precedence. Only if a control further up the hierarchy is not reasonably practicable or is unlikely to be completely effective in controlling the risk can a PCBU move on to a less reliable control. Often the control strategy will include elements at different levels in the hierarchy that combine to meet the overall protection principle. Engineering or system-level controls are sometimes described as being “above the line” while controls that primarily rely on human behaviour are referred to as “below the line”.
Figure 2.2 - Hierarchy of controls
(Source: WorkSafe New Zealand Hazardous Substances Risk Management Chart <>)
A diesel compressor in a workshop was identified as a noise hazard (as well as having other hazards including fumes, drive belts and pressure systems). The compressor supplies air to a number of systems and workers are required to work in close proximity to it. An initial noise assessment indicated that noise levels exceeded those in the Approved Code of Practice.
The hierarchy of controls should be followed to manage the noise risk presented by the compressor, as described below:
The hazard could be eliminated by replacing the compressor with cylinders of compressed air, removing the noise. Whether this is reasonably practicable or not may depend on factors such as whether cylinders can supply the required pressure or volumes of air and the fact that cylinders introduce new hazards of their own including manual handling and pressure vessel hazards. Typically, elimination and substitution controls are best considered as part of health and safety in design and procurement, as it is easier to specify a quieter compressor or choose the location for it before it has been purchased and installed.
If elimination is not reasonably practicable the diesel compressor could be replaced with one powered by a quieter electric motor. Considerations may include capacity, reliability and proximity to a mains power supply. Benefits include no hot exhaust pipes and fumes.
The compressor could then be isolated by building a housing around it to separate it from workers while they carry out their tasks or moving the compressor to outside the building away from areas where other tasks are carried out. Note that even if the compressor is substituted for a quieter alternative, it may still be reasonably practicable to isolate it (and to continue further down the hierarchy of controls).
Engineered controls
Engineered controls could include the installation of an interlock that reduces compressor speed (or shuts it down) when the door to the housing is opened for maintenance access. Such an interlock could also help control mechanical hazards during maintenance tasks.
Procedural controls
Procedural controls could limit the amount of time workers are permitted to spend in close proximity to the compressor. Workers could be trained on health risks from noise and the correct fitting of hearing protection. Warning signs could be posted in the area and information about the noise risk could be included in the Job Safety Analysis or risk assessment for the task.
Personal protective equipment
Finally, protective equipment in the form of suitable hearing protection can be provided. This would need to be selected to reflect the noise profile and to be a comfortable fit for workers, especially in conjunction with other items of PPE. It would need to be periodically maintained or replaced and managers would need to regularly monitor that it is being worn as a matter of routine. Health monitoring would be required to verify that hearing loss has not occurred despite the application of these controls.
At each level of the hierarchy, each potential control should be assessed to determine if it is reasonably practicable. Employing a control at one level does not remove the requirement to consider more if they remain reasonably practicable. As can be seen from this example the below the line controls are not necessarily the cheapest in the long run and are less reliable – yet PPE is typically the first control people think about in relation to a noise hazard.

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