What is the test for contributory negligence on the basis that a design defect in a suction valve caused a plaintiff to lose his hearing?

The trial judge found liability on the part of the appellant on the ground that the suction valve had a design defect that caused the loss. The trial judge also found that the respondent was contributorily negligent to the extent of fifteen percent because he was not wearing safety glasses. The appellant submits that the trial judge erred in finding that injury was caused by the alleged design defect. The respondent cross-appeals the finding of contributory negligence. Both the appeal and the cross-appeal are entirely fact-driven. We are not persuaded that either party has established “palpable and over-riding error” on the part of the trial judge: see Stein v. The Ship “Kathy K” (1975), 1975 CanLII 146 (SCC), 62 D.L.R. (3d) 1 (S.C.C.).