Quantified risk assessment for fall from height

Logical models for quantifying occupational risk owing to fall from height developed under the Workgroup Occupational Risk Model (WORM) project are presented. Sixty four logical models quantifying corresponding occupational risks are developed under the WORM project. The overall objective of quantifying occupational risk through detailed logic models in WORM is twofold: First from a qualitative point of view the model helps in identifying the specific factors that contribute to the risk by outlining the sequence of events that constitute an accident, starting from the undertaking of an activity by a worker to the final undesirable consequence. Second, from a quantitative point of view, a logic model allows for the quantitative assessment of the risk of the particular activity to the workers allowing a rational ordering of the various activities on the basis of quantified risk rather than on, the potentially misleading, number of observed accidents. Furthermore, a quantified detailed logical model allows for the assessment of the relevant contribution of the various factors to the risk enabling this way a rational prioritization of the available risk reducing measures. Fall from height models presented in this paper simulate the logical and stochastic interdependences of the various events involved with the occurrence of a fall and its consequences. Fall from heights logical models consist of two main parts (a) the part incorporating the events preceding the fall consisting mainly of fall preventing measures; and (b) the part incorporating events following the fall and consisting mainly of measures mitigating the effects of the falls or otherwise affecting the consequences of a given fall. Three levels of consequence severity are considered; lethal injuries, non-lethal permanent injuries, and recoverable injuries. A generic logical model developed for quantifying occupational risk is specialized to six particular instances corresponding to six different work related ways of falling from a height, namely falls from ladders, scaffolds, roofs and roof openings, holes in the ground, moveable platforms and falls from non-moving vehicles. Safety measures engineered or procedural aimed at preventing the fall, mitigating the impact of a fall and influencing the consequences of a given impact along with the required data for quantification are presented. As an example preliminary quantification results are presented for the risk of a fall from a movable ladder.