Radiation safety. The maximum permissible exposure levels: our knowledge of the hazards

Many different agencies and standards organizations have proposed laser safety standards and personnel exposure limits (ELs), or maximum permissible exposure (MPE) levels. Safety standards may be limited in scope to codes of practice, to occupational ELs, to laser product safety, or to a combination of these three factors. Initially, in the 1960s, attention was drawn to setting ELs; 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 (AELs) were based upon the ELs. 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 MPEs (that is, ELs) and their basis are highlighted in this presentation.