It is considered a person is (working at heights) at risk of a fall:
Fall means a fall by a person from one level to another
Risk of a fall means a circumstance that exposes a worker while at work, or other person while at or in the vicinity of a workplace, to a risk of a fall that is reasonably likely to cause injury to the worker or other person. This includes circumstances in which the worker or other person is:
1. in or on plant or a structure that is at an elevated level
2. in or on plant that is being used to gain access to an elevated level
3. in the vicinity of an opening through which a person could fall
4. in the vicinity of an edge over which a person could fall
5. on or in the vicinity of a surface through which a person could fall
6. on or near the vicinity of a slippery, sloping or unstable surface.
In those cases all workers should be trained to work safely at heights.