page_title: Laser safety
section_title: Classification
hierarchical_section_title: Laser safety / Classification
caption_attribution_description: English: The maximal allowed cw-powers for the laser classes 1, 2, 3R and 3B according to the norm EN 60825-1:2007. Note that these values hold only for static, point-like laser sources (i.e. collimated or weakly divergent laser beams), for extended or strongly divergent laser sources the powers can be larger. Some missing and some numerical values: 180 nm &lt; λ &lt; 315 nm: for laser class 1 and 3R the limitations are just defined in terms of pulse energy. 500 nm &lt; λ &lt; 700 nm: P &lt; 0.39 mW for laser class 1 and P &lt; 5 mW for class 3R and 500 mW for class 3B. 1700 nm &lt; λ &lt; 4000 nm: the limiting powers are equal to those at λ = 1700 nm.
context_page_description: Laser safety is the safe design, use and implementation of lasers to minimize the risk of laser accidents, especially those involving eye injuries. Since even relatively small amounts of laser light can lead to permanent eye injuries, the sale and usage of lasers is typically subject to government regulations.
  Moderate and high-power lasers are potentially hazardous because they can burn the retina, or even the skin. To control the risk of injury, various specifications, for example 21 Code of Federal Regulations Part 1040 in the US and IEC 60825 internationally, define "classes" of laser depending on their power and wavelength. These regulations impose upon manufacturers required safety measures, such as labeling lasers with specific warnings, and wearing laser safety goggles when operating lasers. Consensus standards, such as American National Standards Institute Z136, provide users with control measures for laser hazards, as well as various tables helpful in calculating maximum permissible exposure limits and accessible exposures limits.
context_section_description: Lasers have been classified by wavelength and power into four classes and a few subclasses since the early 1970s.  The classifications categorize lasers according to their ability to produce damage in exposed people, from class 1 (no hazard during normal use) to class 4 (severe hazard for eyes and skin). There are two classification systems, the "old system" used before 2002, and the "revised system" being phased in since 2002. The latter reflects the greater knowledge of lasers that has been accumulated since the original classification system was devised, and permits certain types of lasers to be recognized as having a lower hazard than was implied by their placement in the original classification system. The revised system is part of the revised IEC 60825 standard. From 2007, the revised system is also incorporated into the US-oriented ANSI Laser Safety Standard (ANSI Z136.1).  Since 2007, labeling according to the revised system is accepted by the FDA on laser products imported into the US. The old and revised systems can be distinguished by the 1M, 2M and 3R classes used only in the revised system and the 2A and 3A classes used only in the old system.  Class numbers were designated using Roman numerals (I–IV) in the US under the old system and Arabic numerals (1–4) in the EU.   The revised system uses Arabic numerals (1–4) in all jurisdictions.
  The classification of a laser is based on the concept of accessible emission limits (AEL) that are defined for each laser class. This is usually a maximum power (in W) or energy (in J) that can be emitted in a specified wavelength range and exposure time that passes through a specified aperture stop at a specified distance. For infrared wavelengths above 4 μm, it is specified as a maximum power density (in W/m²). It is the responsibility of the manufacturer to provide the correct classification of a laser, and to equip the laser with appropriate warning labels and safety measures as prescribed by the regulations. Safety measures used with the more powerful lasers include key-controlled operation, warning lights to indicate laser light emission, a beam stop or attenuator, and an electrical contact that the user can connect to an emergency stop or interlock.
caption: The maximal allowed cw-powers for the laser classes 1, 2, 3R and 3B according to the standard EN 60825-1:2007. Note that these values hold only for static, point-like laser sources (i.e. collimated or weakly divergent laser beams).
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