Lab Safety Guide - Chapter 5: Laser Safety
The following gives an overview of safety, regulations and other topics related to laboratory use of lasers. Adapted from the NMSU Lab Safety Guide (modified - dls)
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The acronym LASER stands for "light amplification by the stimulated emission of radiation." Lasers are devices that produce light at very specific frequencies of the electromagnetic spectrum. The frequency of a laser depends on the type of material that is stimulated. The properties of lasers are similar to those of the other members of the electromagnetic spectrum. However, lasers can achieve great power densities which, along with operating at a single wavelength, has made them indispensable in today's marketplace. Lasers can also present a serious danger to the eyes and skin. Care must be taken to assure the safe operation of lasers.
The Radiation Control for Health and Safety Act of 1968 was passed by Congress to protect the U.S. public from the dangers of radiation exposure from electronic products. Federal regulations require that all laser products. (i.e., any electronic product that consists of, incorporates, or is intended to incorporate a laser) manufactured on or after August 2, 1976, be certified as complying with the FDA performance standards for laser products, 21 CFR 1040.10 and 1040.11 under the Radiation Control for Health and Safety Act. Also reference ANSI Z-136.1-1993 American National Standard Institute 1993.
The Standards created by the FDA divide laser products into four separate classes, based on the biological effect produced by the laser and the intensity of the radiation in the laser beam.
1. Class I lasers produce radiation that causes no biological damage. The continuous output of Class I laser is not more the 0.39 m W.
2. Class II lasers produce radiation that can cause eye damage if exposures are direct and prolonged. The continuous output of a Class II laser is not more than 1 mW. These lasers operate in:
visible (400-700 nm) and continuous wave (CW) bands, and can emit a power exceeding Pexempt for the classification duration (0.4 mW for Tmax> 104s), but not exceeding 1 mW; and
visible (400-700 nm), repetitively pulsed, or scanning modes, which may be evaluated by specifying Pexempt at a point 10 cm from the exit port of the laser system. Such laser devices can emit a power that exceeds the appropriate Pexempt for the classification duration, but not exceeding Pexempt for a 0.25-second exposure.
3. Class III lasers emit radiation that is powerful enough to severely damage the eye and possibly lead to loss of sight from direct or indirect exposures off of shiny surfaces for a short duration (example signs for class 3b). The continuous output of Class III lasers is not more than 500 mW. These medium power laser devices produce radiation in:
a) the infrared (1.4 um-1 mm) and the ultraviolet (200-400 nm) bands and can emit power in excess of Pexempt for the classification duration, but they cannot emit:
an average radiant power in excess of 0.5 W, for Tmax greater than 0.25 seconds or
a radiant exposure of 10 J cm -2 within an exposure duration of 0.25 second or less;
b) visible (400-700 nm) band, CW, or repetitive pulses, modes that produce a radiant power in excess of Pexempt for a 0.25-second exposure (1 mW for CW laser), but they cannot emit an average radiant power of 0.5 W for Tmax greater than 0.25 second;
c) visible and near-infrared (400-1400 nm) bands, and emit a radiant energy in excess of Qexempt but they cannot emit a radiant exposure that exceeds either 10 J cm-2 or that required to produce a hazardous diffuse reflection; and
d) near-infrared (700-1400 nm) CW band, CW, or they and repetitively pulsed modes emit tiny amounts of power in excess of Pexempt for the classification duration, but they cannot emit an average power of 0.5 W or greater for periods in excess of 0.25 second.
4. Class IV lasers emit extremely powerful radiation, which can cause damage to eye and skin tissue when exposures are short and the beam is direct, reflected, or diffused. Direct irradiation from a Class IV laser on the eye will cause permanent damage (danger signs for Class 4 ). The continuous output of a Class IV laser is more than 500 mW. These high power laser devices operate in:
a) ultraviolet (200-400 nm) and infrared (1.4 54m - 1mm) bands emit an average power in excess of 0.5 W for periods greater than 0.25 second or radiant exposure of 10 J cm-2 within an exposure duration of 0.25 second or less; and
b) visible (400-700 nm) and near-infrared (700-1400 nm) bands, and emit an average power of 0.5 W or greater, for periods greater than 0.25 second, or a radiant exposure in excess of either 10 J cm-2, or that required to produce a hazardous diffuse reflection.
Before a laser is purchased, the facility should notify the departmental and Environmental Health and Safety to determine whether its use by laboratory personnel would be safe. The facility operator should design a safe operating procedure for using the laser which includes a short safety course for all potential users. A written examination on eye and laser safety should be given and kept on file.
Typically, lasers require very little monitoring. The manufacturer designates both the power level and the wavelength. With this information, the department can classify the laser into one of the four groups (I-IV) discussed above. Then, the facility can apply the controls based on the designated classification. The American Conference of Governmental Industrial Hygienists (ACGIH) lists the threshold limit values (TLVs) for lasers based on their exposure duration, radiation exposure, irradiance, and wavelength. EH&S can use the Laser Database to help gather this information and apply the proper controls.
Most control measures depend upon a laser's classification (I-V) Listing of laser safety control measures by classification.
Class I exempt laser device is considered to be incapable of producing damaging radiation levels. It is, therefore, exempt from any control measures or other forms of surveillance.
Class II, medium power laser device may be viewed directly. However, it must bear a cautionary label warning against continuous intrabeam viewing.
Class III, medium power laser device requires control measures that will preclude viewing of the beam directly.
Class IV, high power laser device requires control measures that will preclude exposure of eyes as well as skin to the direct and diffusely reflected beam.
Each laser, Class II, III and IV must have a label attached by the manufacturer describing the necessary precautionary measures that must be taken.
The correct labels must also be placed at the entrance to an area utilizing laser energy.
Each laser operator must insure that adequate eye and skin protection is readily available for each researcher and additional naturals available for visitors.
American National Standard Institute, Safe use of Laser, ANSI Z136.1-1993, New York.
Laser Institute of America, Laser Safety Guide, Fifth Printing, January 1992.
Laser safety procedures, sample cases, written eye
safety exam, and eye-laser interaction discussions can be found in:
Matthews and Garcia, Laser and Eye Safety in the Laboratory, IEEE Press, Piscataway, New Jersey.