Deriving exposure limits

Historically, many different agencies and standards organizations have proposed laser occupational exposure limits (EL's), or maximum permissible exposure (MPE) levels. Although some safety standards have been limited in scope to manufacturer system safety performance standards or to codes of practice, most have included occupational EL's. Initially, in the 1960's, attention was drawn to setting EL's; however, as greater experience accumulated in the use of lasers and some accident experience had been gained, safety procedures were developed. It became clear by 1971, after the first decade of laser use, that detailed hazard evaluation of each laser environment was too complex for most users, and a scheme of hazard classification evolved. Today, most countries follow a scheme of four major hazard classifications as defined in Document WS 825 of the International Electrotechnical Commission (IEC). The classifications and the associated accessible emission limits (AEL's) were based upon the EL's. The EL and AEL values today are in surprisingly good agreement worldwide. There exists a greater range of safety requirements for the user for each class of laser. The current MPE's (i.e., EL's) and their basis are highlighted in this presentation.