Probabilistic risk assessment in the development of laser safety standards Available to Purchase

Since the development of the first ANSI Z136.1 standard (1973), estimates of risk of ocular exposure have been employed by safety standards committees to develop the hazard classes and to determine the appropriate control measures for each class. Indeed, probabilistic risk assessment (PRA) was used to argue for setting the AELs for Class 3a and for Class 3b. The setting of 0.25 s as the aversion response was based on an analysis of the interplay of several physiological factors and probability of several worst-case conditions occurring at the same time. In the first laser safety standards, it was argued that diffuse reflection hazards did not vary with viewing distance and the AELs for Class 3b were based upon the sudden jump in the probability of viewing a hazardous level. PRA was particularly important in the development of safety standards for military lasers (and lasers used outdoors); guidelines for setting buffer zones and in dealing with atmospheric scintillation all were based upon such risk assessments in the safety standards committees. The general philosophy developed in the US has been for a committee of experts to consider risk factors and to provide practical guidance, and not to suggest that users perform a PRA. There is a renewed need for safety standards committees to employ PRA to determine more realistic measurement conditions for optically aided viewing—particularly with regard to the concept of measurement “Condition 2” for magnifier viewing of a diverging beam. PRA should also be applied rather than “worst-case” analysis in the development of guidelines for the safe use of Class 1M lasers in outdoor free-space communications.