Rationale for laser classification measurement conditions

The basic concept of laser hazard classification with four fundamental risk groups and several subclasses is well understood by most laser users. However, many readers of laser safety standards are frequently puzzled by the rigid measurement conditions applied for hazard classification, even if this is normally a task performed by the laser manufacturer and not by a laser user or a Laser Safety Officer. The historical rationale for the measurement conditions is provided and it is emphasized that the aim of each measurement is to simulate a wide range of ocular exposure conditions that would be reasonably foreseeable worst-case viewing conditions during the use of the laser product. Measurements, if needed to compare human exposures with the maximum permissible exposure limits, emphasize actual exposure conditions and generally do not match the measurement used for hazard classification.