Employers and self-employed persons must, as far as reasonably practicable, find every hazard linked to confined space work (ss 21, 23, 24). They may do this once for a class of like confined spaces rather than space by space, but only where every space in that class is alike and doing so leaves no employee exposed to any greater, extra or different risk than individual identification would.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.