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Environmental Health and Safety


Coherent Light – Lasers

Lasers generate coherent, monochromatic light in many wavelengths, both visible and invisible, depending on the type of laser. The property of coherence makes lasers very different than typical light sources; and very hazardous to the eyes and/or skin.

The properties of coherence makes lasers hazardous even at very low powers. Some lasers operating at a power of just a few milliWatts (mW) or less can cause instantaneous damage to the eye and/or skin if exposed. Because laser light is monochromatic and coherent, the distances with which lasers can be hazardous are quite long; typically miles long.

The United States Federal Performance Standards for Light Emitting Products requires manufacturers and/or importers of laser devices to assign a hazard class to all lasers distributed for use. All lasers must have a durable label on the device with the hazard class indicated.

All lasers used on University property must have the hazard class label clearly legible on the device. The laser hazard classes and their meaning are below:

  • Class 1: Eye safe. Lasers classed as Class 1 are low enough in power that damage to the eyes are not possible.
  • Class 1M: Eye safe except if altered by optical aides.
  • Class 2: Eye safe taking into account the reflexive aversion response to a damaging light source. The reflexive response to limit damage to the eye is fast enough to ensure that if a Class 2 laser beam enters the eye, damage will not occur. Class 2 lasers therefore must be in the wavelength of visible light.
    Many laser pointers and bar code scanners, such as those at retail outlets and grocery stores, are Class 2 lasers.
  • Class 2M: Eye safe taking into account the reflexive aversion response; except if altered by optical aides.
  • Class 3R: Marginally unsafe for intrabeam viewing. The “R” stands for reduced hazard.
  • Class 3R lasers are not controlled for use by the University. However, if you are utilizing a laser classed as 3R, precautions must be taken to ensure that the beam is not directed into the eyes of anyone.
    Some laser pointers are Class 3R.
  • Class 3B: Unsafe for intrabeam viewing. Specularly reflected beams are hazardous. Engineering and/or administrative controls must be in place to ensure that individuals operating the laser; and in the vicinity of the beam, are protected. Training is required for all operators of Class 3B lasers.
  • Class 4: Unsafe for intrabeam viewing. All specular and diffuse reflections of Class 4 beams are hazardous. Class 4 laser powers can be high enough to transfer enough heat onto objects where fires can begin. Engineering and/or administrative controls must be in place to ensure to ensure that individuals operating the laser; and in the vicinity of the beam, are protected. Training is required for all operators of Class 4 lasers.

The University possesses many Class 3B and 4 lasers for research and development purposes. Procedures must be in place and in conformance with the American National Standards for the Safe Use of Lasers in Research, Development, or Testing (ANSI Z136.8). All operators of Class 3B and 4 lasers must be trained.

The University’s Radiation Safety Office coordinates laser safety program development in conjunction with the Principal Investigator (PI) and research staff where Class 3B and 4 lasers are utilized. Should you need to purchase equipment containing a Class 3B or 4 laser, have any questions pertaining to the use of lasers, need to deactivate equipment containing an Class 3B or 4 laser, or have general questions regarding laser devices, please contact the Radiation Safety Office at 803-777-2841 or 803-777-7530.

Laser Safety forms can be found at the Radiation Safety Toolbox Page.

The University’s Laser Safety Program can be found in the University’s Radiation Safety Manual [pdf].

Laser safety training programs can be found at the Research Safety Bureau’s training page for Radiation Safety.