Probabilistic Risk Assessment (PRA) techniques are an increasingly-accepted alternative to standard hazard assessments based on Maximum Permissible Exposure (MPE) limits, where the use of high-output military lasers in outdoor environments is concerned. The adoption of a probabilistic approach is motivated by the relative inflexibility of a deterministic evaluation, in which a laser exposure is simply characterised as either “safe” or “unsafe” in comparison with the applicable MPE. The probabilistic method is alternately predicated on the socio-economic acceptability of a low risk of very minor levels of laser-induced injuries.
The United Kingdom Ministry of Defence initiated the development of probabilistic laser hazard assessment models in the mid-1970s, while the United States Air Force has had the goal of developing probabilistic hazard assessment methods for High Energy Laser (HEL) Range testing purposes since the late 1990s. HEL Range clearances evaluated using an MPE-based approach would be virtually impracticable, due to the extraordinarily-large hazard areas involved. The purpose of this paper is to show that a probabilistic hazard analysis is underpinned by the same risk assessment process as the deterministic approach, with the method of choice dependent on the nature of the laser hazard and the risk management context.