CLASSIFICATIONS OF LASERS

There are 4 main classifications of lasers. These classifications are for lasers in the general sense, not specifically in reference to how they are used in health, medicine and surgery. Classes II, III and IV are required to have a safety label with respective warnings printed. (11)

  • “Laser hazard classification gives the user or laser safety officer an initial sense of the hazard the laser system or product presents to the user and others in the area. Rather than using colors to alert one to the fire hazard level in laser safety, a numerical code is used. The higher the number, the greater the hazard potential. Potential is the key word, for any laser system can be made safe.” (12)

Each Classification is defined below, with a summary explanation, quotes from quality sources which are cited at the bottom, and respective examples. Specific lasers of each class that are commonly used for medical and surgical purposes are listed on THIS page.

Key for acronyms and symbols used below:

  • µm = micrometer
  • mW = milliwatt
  • Watt = flow of Joules per second
  • Joules = unit of energy used in measuring lasers
    • More specifically: “One joule is equal to the energy used to accelerate a body with a mass of one kilogram using one newton of force over a distance of one meter. One Joule is also equivalent to one watt/second.”
  • AEL: Accessible Emission Limit
  • NOHA = Nominal Ocular Hazard Area
    • Within this area, “the intensity or the energy per surface unit is higher than the MPE on the cornea. The size of this area is defined by the NOHD. (8)
  • NOHD = Nominal Ocular Hazard Distance
    • The distance along the laser beam axis beyond which is acceptable for eye exposure (7)
  • MPE = Maximum Permissible Exposure
    • The highest laser energy to which the eye or skin can be exposed for a given laser (7)
  • CW = Continuous Wave
  • Optical aids = binoculars, telescopes, microscopes, magnifying glasses (but not prescription glasses) (13)

Class I

    • SUMMARY: In all foreseeable circumstances, lasers classified as Class I are understood to be safe in every aspect (skin, eyes, general health, etc.), meaning there are no safety requirements. Lasers of this class can be within both the visible and invisible spectrum.
    • SOURCED QUOTES:
      • “Considered non-hazardous” (1)
      • “Are very low risk and ‘safe under reasonably foreseeable use’, including the use of optical instruments for intrabeam viewing.” (4)
      • “Classes 1 and 1M can be visible, invisible or both” (13)
      • The following are cited from (6)
        • Type of lasers:
          • Very low power lasers or encapsulated lasers
        • Meaning:
          • Safe
        • Relationship to MPE:
          • MPEs are not exceeded, even for long exposure duration (either 100 seconds or 30,000 seconds), even with the use of optical instruments)
        • Hazard area:
          • No hazard area (NOHA)
        • Typical AEL for CW Lasers:
          • 40µW for blue”
    • EXAMPLES:
      • Laser printers (11)
      • CD players (11)
      • Geological survey equipment (11)
      • Laboratory analytical equipment (11)
    • Class IM
        • SUMMARY: Lasers classified as Class I M are between 302.5nm and 400nm (overlapping slightly in both the visible and invisible range) and are safe for exposure, except when viewed through any optical aid which magnifies. Under the circumstance of lasers of this class being viewed under magnification, potential eye damage is possible.
        • SOURCED QUOTES:
          • “Hazard increases if viewed with optical aids, including magnifiers, binoculars, or telescopes, potentiating eye damage under these circumstances” (1)
          • “Wavelengths between 302.5nm and 400nm, and are safe except when used with optical aids” (4)
          • “Classes 1 and 1M can be visible, invisible or both” (13)
          • The following are cited from (6)
            • Type of lasers:
              • Very low power; either collimated with large beam diameter or highly divergent
            • Meaning:
              • Safe for the naked eye, potentially hazardous when optical instruments are used
            • Relationship to MPE:
              • MPEs are not exceeded, even for the naked eye, even for long exposure durations, but maybe exceeded with the use of optical instruments
            • Hazard area:
              • No hazard area for the naked eye, but hazard area for the use of optical instruments (extended NOHA)
            • Typical AEL for CW Lasers:
              • Same as Class 1, distinction with measurement requirements”
          • EXAMPLES:
            • LED
            • Laser printers (1)
            • CD/DVD players (1)

Class II

    • SUMMARY: Lasers classified as Class II are between the wavelengths of 400nm and 700nm (visible light spectrum), operate under 1mW of power, and are generally considered safe, though prolonged staring should be avoided. In other words, lasers of this classification are safe within the exposure of the natural human eye aversion rate (how quickly your eyes blink), which is a duration of 0.25 seconds.
    • SOURCED QUOTES:
      • “Visible lasers considered incapable of emitting laser radiation at levels that are known to cause skin or eye injury within the time period of the aversion response (0.25 seconds)” (5)
      • “Repetitively pulsed lasers with wavelengths between 0.4µm and 0.7 µm that can emit energy in excess of the Class 1 AEL, but do not exceed the Class 1 AEL for an emission duration of less than 0.25 seconds and have an average radiant power of 1mW or less” (3)
      • “Do not permit human access to exposure levels beyond the Class 2 AEL for wavelengths between 400nm and 700 nm. Any emissions outside of this wavelength region must be below the Class 1 AEL” (4)
      • “Are low power (<1mW)” (11)
      • “Class 2M-These are visible lasers… classes 2 and 2M [are] visible, but also can contain an invisible element, subject to certain conditions.” (13)
      • The following are cited from (6)
        • “Type of lasers:
          • Very low power lasers
        • Meaning:
          • Safe for unintended exposure, prolonged staring should be avoided
        • Relationship to MPE:
          • Blink reflex limits exposure duration to nominally 0.25 seconds. MPE for 0.25 seconds not exceeded, even with the use of optical instruments
        • Hazard area:
          • No hazard area when based on unintended exposure (0.25 seconds exposure duration)
        • Typical AEL for CW Lasers:
          • 1 mW”
    • EXAMPLES:
      • Barcode scanners (1)
      • Some laser pointers (11)
      • Aiming devices (11)
      • Range finding equipment (11)
    • Class II A
      • SUMMARY: Lasers of the classification II A are considered safe. They are not intended to be stared at, however they are not known to produce any eye or skin damage during normal operation of a device of this classification, under a duration of 1000 seconds (16 2/3 minutes)
      • SOURCED QUOTES:
        • “Visible lasers that are not intended for viewing and cannot produce any known eye or skin injury during operation based on a maximum exposure time of 1000 seconds” (5)
      • EXAMPLE:
        • CoMra-Therapy is classified as a class II A laser.
          • For explanation on this device, scroll to the bottom of THIS page to CoMra-Therapy
          • To purchase this device, see HERE
    • Class II M
        • SUMMARY: Lasers of the classification II M are considered safe, but do not view through any magnifying device. Class II M lasers not known to cause any skin damage, and are not known to cause any eye damage within the natural time it takes for the human eye to blink, except when viewed through magnification.
        • SOURCED QUOTES:
          • “Not known to cause eye or skin damage within the aversion response time unless collecting optics are used” (5)
          • “Have wavelengths between 400nm and 700 nm, and are potentially hazardous when viewed with an optical instrument. Any emissions outside this wavelength region must be below the Class 1M AEL.” (4)
          • The following are cited from (6)
            • “Type of lasers:
              • Visible low power lasers; either collimated with large beam diameter or highly divergent
            • Meaning:
              • Same as Class 2, but potentially hazardous when optical instruments are used
            • Relationship to MPE:
              • MPEs for 0.25 seconds not exceeded for the naked eye, but maybe exceeded with the use of optical instruments
            • Hazard area:
              • No hazard area for the naked eye when based on accidental exposure (0.25 seconds exposure duration), but hazard area for the use of optical instruments (extended NOHA)
            • Typical AEL for CW Lasers:
              • Same as Class 2, distinction with measurement requirements”
        • EXAMPLES:
          • No specific examples could be found of 2M specifically versus Class II. If found otherwise, please contact the ADMIN.

Class III

  • Class III R (“relaxed”)
      • SUMMARY: Class III R replaced what used to be referred to as Class III A in most classification sources (still defined below for clarity purposes). Lasers classified as III R range from 302.5nm to 106nm and emit between 1mW and 5 mW of power. Lasers in this class are safe when handled carefully, but are not meant to be directly viewed; risk of eye damage increases when viewed directly with a source of magnification.
      • SOURCED QUOTES:
        • “Replaces Class 3A and has different limits. Up to 5 times the Class 2 limit for visible and 5 times the Class 1 limits for some invisible” (5)
        • “Depending on power and beam area, can be momentarily hazardous when directly viewed or when staring directly at the beam with an unaided eye. Risk of injury increases when viewed with optical aids.” (1)
        • “Range from 302.5nm and 106nm, and is potentially hazardous but the risk is lower than that of the Class 3B lasers. The accessible emission limit is within 5 times the Class 2 AEL for wavelengths between 400 nm and 700 nm, and within 5 times the Class 1 AEL for wavelengths outside this region.” (4)
        • “CW visible lasers emitting between 1 and 5 mW are normally Class 3R” (13)
        • The following are cited from (6)
          • Type of lasers:
            • Low power lasers
          • Meaning:
            • Safe when handled carefully. Only small hazard potential for accidental exposure
          • Relationship to MPE:
            • MPEs with naked eye and optical instruments may be exceeded up to 5 times
          • Hazard area:
            • 5 times the limit of Class 1 in UV and IR, and 5 times the limit for Class 2 in visible, i.e. 5 mW
          • Typical AEL for CW Lasers:
            • 5 times the limit of Class 1 in UV and IR, and 5 times the limit for Class 2 in visible, i.e. 5 mW”
      • EXAMPLE:
        • Some laser pointers (1)
  • Class III A
    • SUMMARY: Class III A was replaced by Class III R in most classification sources, also by 1M and 2M under IEC and EN classification, though is still defined here for clarity.
    • SOURCED QUOTES:
      • “Lasers similar to Class 2 with the exception that collecting optics cannot be used to directly view the beam; Visible [light] only” (5)
      • “Have an accessible output between 1 and 5 times the Class 1 AEL for wavelengths shorter than 0.4 µm or longer than 0.7 µm, or less than 5 times the Class 2 AEL for wavelengths between 0.4 µm and 0.7 µm” (3)
      • “Are continuous wave, intermediate power (1-5 mW) devices” (11)
      • “Classes 1M and 2M broadly replace the old class 3A under IEC and EN classification.” (13)
    • EXAMPLES:
      • Laser pointers (11)
      • Laser scanners (11)
  • Class III B
    • SUMMARY: Lasers classified as III B pose a slight increase of risk as opposed to III R. Lasers of this class can be in the visible or invisible spectrum and pose a potential eye hazard for direct viewing and also can be a potential eye hazard when viewed from a reflective source (i.e. from a mirror or anything capable of a reflective surface) less than 13cm away for more than 10 seconds. For usage of lasers in this classification, protective eyewear, key switches on the device, and safety interlocks on the device are all required. Lasers of this class are below a power of 2 Watts per second of exposure (or .5 Joules). Most lasers in this class do not pose a significant skin hazard, though some higher powered lasers still within this classification can pose some risk. Lasers in this class can heat skin and other materials but are not considered a burn hazard.
    • SOURCED QUOTES:
      • “Medium powered lasers (visible or invisible regions) that present a potential eye hazard for intrabeam (direct) or specular (mirror-like) condition. Class 3B lasers do not present a diffuse (scatter) hazard or significant skin hazard except for higher powered 3B lasers operating at certain wavelength regions” (5)
      • “Cannot emit an average radiant power greater than 0.5 Watts for an exposure time equal to or greater than 0.25 seconds or 0.125 Joules for an exposure time less than 0.25 seconds for wavelengths between 0.18 µm and 0.4 µm, or between 1.4 µm and 1mm. In addition, lasers between 0.4 µm and 1.4 µm exceeding the Class 3A AEL cannot emit an average radiant power greater than 0.5 Watts for exposures equal to or greater than 0.25 seconds, or a radiant energy greater than 0.03 Joules per pulse.” (3)
      • “Are normally hazardous under direct beam viewing conditions, but are normally safe when viewing diffuse reflections.” (4)
      • “Are hazardous to the eye when viewed directly.  For visible and infrared devices, emission power is limited to 0.5W. Protective eyewear, key switches, and safety interlocks are required safety features.” (10)
      • “Are intermediate power (CW 5-500 mW or pulsed 10 J/cm2) devices” (11)
      • “Medium and high power visible and nonvisible – Direct intrabeam viewing of these are always hazardous. Viewing diffuse reflections is normally safe provided the eye no closer than 13 cm from the diffusing surface and the exposure is less than 10 seconds.” (12)
      • The following are cited from (6)
        • Type of lasers:
          • Medium power lasers
        • Meaning:
          • Hazardous when eye is exposed. Wear eye protection within NOHA. Usually no hazard to the skin. Diffuse reflections usually safe
        • Relationship to MPE:
          • Ocular MPE with naked eye and optical instruments may be exceeded more than 5 times. Skin MPE usually not exceeded
        • Hazard area:
          • Hazard area for the eye (NOHA), no hazard area for the skin
        • Typical AEL for CW Lasers:
          • 500 mW”
    • EXAMPLES:
      • Laser light show projectors (1)
      • Industrial lasers (1)
      • Research lasers (1)
      • Some uses for this class include spectrometry, stereolithography, and entertainment light shows (11)
  • Class IV
    • SUMMARY: Lasers classified as Class IV range in the visible and invisible spectrum and operate between 0.5Watts to 15Watts. Lasers of this class are always considered a hazard to the eye, with direct and indirect viewing (i.e. viewed from any source of reflection), so eye protection must always be worn during operation of this class of laser. Eye protection is required, and key switches and safety interlocks on lasers of this classification are also required safety features. Class IV lasers are also considered a fire hazard as they do have the ability to start a fire. This obviously means that lasers of this class can cause burning of the human skin when used improperly. The high majority of Laser Therapy lasers used in clinics are of this class though, as when they are used properly certain lasers of this class can have significant healing properties. For more information see LASER THERAPY.
    • SOURCED QUOTES:
      • “High powered lasers (visible or invisible) considered to present potential acute hazard to the eye and skin for both direct (intrabeam) and scatter (diffused) conditions. Also have potential hazard considerations for fire (ignition) and byproduct emissions from target or process materials” (5)
      • “exceed the Class 3B AEL” (3)
      • “Are hazardous under both intrabeam and diffuse reflection viewing conditions. They may cause also skin injuries and are potential fire hazards.” (4)
      • Operate between 500 mW and 7,500 mW (9)
      • “Includes all lasers that emit powers in excess of the IIIB limitation of one half of one-watt. Eye protection is needed to limit both direct and diffuse reflected exposure. Key switches and safety interlocks are also required safety features. The majority of scientific, industrial, military, and surgical lasers are in this category.” (10)
      • The following are cited from (6)
        • Type of lasers:
          • High power lasers
        • Meaning:
          • Hazardous to eye and skin, also diffuse reflection may be hazardous. Protect eye and skin. Fire hazard
        • Relationship to MPE:
          • Ocular and skin MPE exceeded, diffuse reflections exceed ocular MPE
        • Hazard area:
          • Hazard area for the eye and skin, hazard are for diffuse reflections
        • Typical AEL for CW Lasers:
          • No limit”
    • EXAMPLE:
      • Laser light show projectors (1)
      • Industrial lasers (1)
      • Research lasers (1)
      • SURGICAL:
        • Lasers used to perform LASIK eye surgery (1)
      • THERAPEUTIC:
        • Lite Force Laser (10)

 For Common Terms used in reference to Laser Therapy, see LASERS IN MEDICINE page 

SOURCES:

  1. http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/HomeBusinessandEntertainment/LaserProductsandInstruments/ucm116362.htm
  2. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?FR=1040.10
  3. https://www.rli.com/resources/articles/classification.aspx ** As defined by the American National Standards Institute (ANSI): “an organization for which expert volunteers participate on committees to set industry consensus standards in various fields.”
  4. https://www.rli.com/resources/articles/classification.aspx ** As defined by the International Electrotechnical Commission (IEC), “a global organization that prepares and publishes international standards for all electrical, electronic and related technologies. The IEC document 60825-1 is the primary standard that outlines the safety of laser products. Classification is based on calculations and determined by the AEL as with the ANSI standard, but the IEC standard also incorporates viewing conditions.”
  5. https://www.rli.com/resources/articles/classification.aspx ** Comparison of Classifications
  6. https://www.rli.com/resources/articles/classification.aspx ** Overview of Laser Safety Classes
  7. https://www.osha.gov/dte/library/radiation/laser_rmcoeh_20021007/slide13.html
  8. http://www.optique-ingenieur.org/en/courses/OPI_ang_M01_C02/co/Contenu_09.html
  9. http://www.promotionphysio.com/laser/39-laser/105-history-of-laser-therapy-it-started-with-albert
  10. http://www.litecure.com/companion/2013/07/what-do-the-laser-classifications-actually-mean/
  11. http://ehs.uky.edu/radiation/laser_fs.html
  12. http://www.industrial-electronics.com/Laser_Safety_01.html
  13. http://www.lasermet.com/resources/classification_overview.php

 

For anyone who wishes to look at a specific wavelength (nm) and correlated power (Joules), visit here: http://www.fda.gov/downloads/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/SurgicalandTherapeutic/UCM135800.pdf

Additional Helpful Sources not specifically cited above: