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Evolving issues in laser safety.

The approach to laser safety has come a long way since the 1960s when the first guidelines were issued by defense research organizations in the US and the UK, and then by the American Conference of Governmental Industrial Hygienists. Although the search for 'eye-safe' numbers continues in a few laboratories, this work is almost exclusively centered on deriving retinal thresholds for ultra-short (sub-nanosecond) lasers. Setting limits in this temporal region has been difficult, since there are conflicting data sets and there is a limited amount of data to extrapolate to other spectral regions. In the standards arena, the concentrated efforts have been in terms of product classification and attempts to resolve the eternal question of 'how safe is safe?'. Recent efforts to revise safety standards have not always taken into account the historical rationale for the maximum permissible exposures and forget that safety factors were already factored into the limits and further safety factors are quite unnecessary. Finally, the study of accidents raises the question of whether our approach to eye protection and enclosures are adequate and whether separate standards and guidance is needed for different applications.