Australia Model Code of Practice: Managing the Risks of Plant in the Workplace 4.1a: 4.1 Guard plant using the required order of barrier types (r 208)

Where guarding is used, the person with management or control must use a permanently fixed barrier if access to the guarded area is not needed during operation, maintenance or cleaning; where access is needed, an interlocked physical barrier that allows access only when the area presents no risk. If neither is reasonably practicable, use a physical barrier that can only be altered or removed with a tool; and if that is also not reasonably practicable, use guarding that includes a presence-sensing safeguarding system that eliminates the risk when a person or part of a person is in the guarded area. Fixed barriers are welded or built into the machine, such as enclosing gears. An interlock guard connects to operational controls so the plant cannot run until the guard is closed, and either stays locked while running with a delay until moving parts stop, or stops the machine when opened. Fixed in position barriers should be removable only with a special tool that is not the operator's normal tool, and devices operated by fingers such as wing nuts should not be used. Perimeter fences need secured gates or interlocks, and an interlocked door closed by accident should not restart the machine. Adjustable guards allow material feed while preventing contact.