Where a structure has multiple components, a known defect in one component does not establish reasonable foreseeability of injury from a defect in a different, unrelated component. The 'class of injury' foreseeability doctrine (Mount Isa Mines v Pusey; Chapman v Hearse) applies to the type of harm suffered, not to the source of danger — a defect in one part of a structure 'heralded nothing as to a possible defect in the other'. An occupier who engages a specialist to maintain equipment is entitled to assume that safety issues are being addressed by that specialist, absent evidence to the contrary.
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