To provide a basis for laser safety requirements, all lasers and laser systems in the United States are classified according to the ANSI Z136.1 standard and the Federal Laser Products Performance Standard (FLPPS). The manufacturer is responsible for determining the laser classification. The builder must classify custom-built and modified lasers. EHS can assist with the classification of such lasers. The ANSI Z136.1 standard is enforced by the Occupational Safety and Health Administration (OSHA). The Laser Products Performance Standard is enforced by the Centers for Devices and Radiological Health (CDRH), a part of the Food and Drug Administration (FDA).
The following section describes the classification for continuous-wave lasers. The same hazard levels also apply to pulsed lasers with pulse duration of less than 0.25 seconds but classification is more complex. See ANSI Z136.1 for details of the classification. Copies of ANSI Z136.1 can be purchased from the Laser Institute of America.
Class 1 Lasers
Class 1 lasers are low-powered and do not emit hazardous radiation under normal operating conditions because they are completely enclosed. Class 1 lasers are exempt from any control measures. Equipment, such as laser printers and laser disc players, are examples of this class. These lasers may present hazards if the housing is breached for maintenance (See Embedded Lasers).
Class 2 Lasers
Class 2 lasers are visible continuous wave (CW) and repetitive-pulse lasers or laser systems which can emit accessible radiant energy exceeding the appropriate Class 1 AEL but less than 1 mW. The human eye blink reflex, which occurs within 0.25 seconds, provides adequate protection for Class 2 lasers. However, it is possible to overcome the blink response and stare into the Class 2 laser long enough to damage the eye. Class 2 lasers are typically exempt from control measures other than having a protective housing and label. Equipment such as some visible continuous wave Helium-Neon lasers and some laser pointers are examples of Class 2 lasers.
Class 3a Lasers
Class 3a lasers are systems with power levels of 1 to 5 mW that normally would not produce a hazard if viewed for only momentary periods with the unaided eye. They can pose severe eye hazards when viewed through optical instruments (e.g., microscopes, binoculars, or other collecting optics). Class 3a lasers must be labeled. A warning label shall be placed on or near the laser in a conspicuous location and caution users to avoid staring into the beam or directing the beam toward the eye of individuals. Equipment, such as some visible continuous wave Helium-Neon lasers and some solid state laser pointers, are examples of Class 3a lasers. It is recommended that no pointers over Class 3a be used at the University of Iowa.
Class 3B Lasers
Class 3B lasers are systems with power levels of 5 mW to 500 mW for continuous wave lasers or less than 10 J/cm2 for a 0.25 s pulsed laser. These lasers will produce an eye hazard if viewed directly. This includes intrabeam viewing or specular reflections. Higher power lasers in this class will also produce hazardous diffuse reflections. See Laser Usage Requirements for specific usage requirements for Class 3B lasers.
Class 4 Lasers
Class 4 lasers are systems with power levels greater than 500 mW for continuous wave lasers or greater than 10 J/cm2 for a 0.25 s pulsed laser. These lasers will produce eye, skin and fire hazards. This includes intrabeam viewing, specular reflections or diffuse reflections. See Laser Usage Requirements for specific usage requirements for Class 4 lasers.
Embedded lasers are found in laser products with lower class ratings. Laser printers, CD players, and laser welders may have Class 3B or Class 4 lasers in their protective and interlocked housings. When such a laser system is used as intended, the lower laser class applies. When such a system is opened (e.g., for service or alignment) and the embedded laser beam is accessible, the requirements for the higher class of the embedded laser must be implemented.