Laser Safety
I. IntroductionII. Scope
III. Responsibilities
IV. Personnel Training and Qualification
V. Exposure Incidents
VI. Laser Hazard Analysis
VII. Laser Classification
VIII. General Laser Safety Recommendations and Requirements
IX. Additional Controls for Class 1 and Class 2 Lasers
X. Additional Controls for Class 3 and 4
XI. Converting to a Class 1 Enclosed Laser
XII. Controlling Associated Hazards
I. INTRODUCTION
The purpose of this program is to insure the safe use of lasers in research by identifying hazards, providing recommendations for proper use, providing for medical surveillance and for laser safety training for individuals using lasers. To achieve this goal, the University has adopted the American National Standard for the Safe Use of Lasers, ANSI Z136.1-2000. ANSI Z136.1-2000 is recognized as a minimum standard for laser safety. Additional information can also be obtained from the Laser Institute of America, located at the following web site: http://www.laserinstitute.org
Most lasers are capable of causing eye injury to anyone who looks directly into the beam or specular reflections. In addition, diffuse reflection of a high-power laser beam can produce permanent eye damage. High-power laser beams can burn exposed skin, ignite flammable materials, and activate toxic chemicals that release hazardous fumes, gases, debris, and radiation. The equipment and optical apparatus required to produce the lasing action and control and direct the laser beam also introduce additional hazards associated with high voltage, high pressure, cryogenics, noise, radiation, and toxic gases.
II. SCOPE
The requirements and recommended details of this program are applicable to all lasers used in research and instructional laboratories at the University of Utah.
III. RESPONSIBILITIES
-
3.1 Principal Investigators are responsible for:
-
1. The immediate supervision of lasers in the laboratory.
2. Providing, implementing, and enforcing the safety recommendations and requirements prescribed in this program.
3. Providing laser operators with training in the administrative, alignment and standard operating procedures.
4. Classifying and labeling all of their lasers.
5. Ensuring the availability of correct protective eyewear.
6. Conducting or coordinating laser safety training for personnel who are assigned to an area where lasers are operated.
7. Participating in University sponsored Laser Safety Training.
8. Notifying EHS immediately in the event of an exposure to a Class 3 or Class 4 laser.
-
1. Following laboratory administrative, alignment and standard operating procedures while operating lasers.
2. Keeping the Principal Investigator fully informed of any departure from established safety procedures. This includes notification of an exposure incident.
3. Participating in University sponsored Laser Safety Training.
-
4.1 Only a qualified and authorized person is permitted to operate a laser. The Principal Investigator determines the employee's operational qualification from departmental or technical training or other acceptable learning experience.
4.2 Before operating a Class 3 or Class 4 laser, or a Class l laser system that encloses a Class 3 or Class 4 laser a person must:
-
1. Review the Laser Safety Program.
2. Receive from the lab supervisor or Principal Investigator a thorough review of the laser equipment to be used and the administrative, alignment and standard operating procedures (SOP's).
3. Review the operating and safety instructions furnished by the manufacturer.
-
5.1 If an exposure incident occurs, EHS must be notified by the Principal Investigator or the person operating the laser.
5.2 If the incident causes an injury or could potentially have caused an injury, the person or persons who have received an exposure should inform their supervisor and be seen immediately by an ophthalmologist or qualified medical professional. The Workers Compensation First Report of Injury must be completed as soon as possible.
5.3 EHS will conduct an investigation, and an incident report will be written.
Before appropriate controls can be selected and implemented, laser radiation hazards must be identified and evaluated.
-
6.1 Types of hazards include:
-
1. Eye : Acute exposure of the eye to lasers of certain wavelengths and power can cause corneal or retinal burns (or both). Chronic exposure to excessive levels may cause corneal or lenticular opacities (cataracts) or retinal injury.
2. Skin : Acute exposure to high levels of optical radiation may cause skin burns; while carcinogenesis may occur for ultraviolet wavelengths (290-320 nm).
3. Chemical : Some lasers require hazardous or toxic substances to operate (i.e., chemical dye, Excimer lasers).
4. Electric shock : Most lasers produce high voltages that can be lethal.
5. Fire hazards : The solvents used in dye lasers are flammable. High voltage pulse or flash lamps may cause ignition. Flammable materials may be ignited by direct beams or specular reflections from high power continuous wave (CW) infrared lasers.
6.3 Maximum Permissible Exposure (MPE): The level of laser radiation to which a person may be exposed without hazardous effect or adverse biological changes in the eye or skin. The criteria for MPE for the eye and skin are detailed in ANSI Z136.1-2000.
-
7.1 Lasers are generally classified and controlled according to the following criteria:
-
1. Class 1 : Low-power lasers and laser systems that cannot emit radiation levels greater than the Maximum Permissible Exposure (MPE). Class 1 lasers and laser systems are incapable of causing eye damage and are therefore exempt from any control measures.
2. Class 2: Visible, low power lasers or laser systems that are incapable of causing eye damage unless they are viewed directly for an extended period (greater than 1000 seconds).
3. Class 3 : Medium-power lasers and laser systems capable of causing eye damage with short-duration (<0.25 s) exposures to the direct or specularly reflected beam. Includes Class 3a and 3b lasers.
4. Class 3a : Lasers or lasers systems that normally would not produce a hazard if viewed for only momentary periods with the unaided eye. They may present a hazard if viewed using collecting optics.
5. Class 3b : Lasers or lasers systems that can produce a hazard if viewed directly. This includes intrabeam viewing of specular reflections.
6. Class 4: High power lasers and laser systems capable of causing severe eye damage with short-duration (<0.25 s) exposures to the direct, specularly reflected, or diffusely reflected beam. Class 4 lasers and laser systems are also capable of causing severe skin damage and igniting flammable and combustible materials.
-
8.1 Eye Protection: Principal Investigators or staff who operate or supervise the operation of a laser are responsible for determining the need for laser eye protection for a particular laser. If required, eye protection will be provided by the supervisor for staff and visitors to the area. The booklet "Guide for the Selection of Laser Eye Protection" produced by the Laser Institute of America may provide assistance in eyewear selection.
8.2 The minimum laser radiant energy or laser power level required for the application should always be used.
8.3 Beam Control : To minimize direct eye exposure, observe these precautions:
-
1. Do not intentionally look directly into the laser beam or at a specular reflection, regardless of its power.
2. Terminate the beam at the end of its useful path.
3. Locate the beam path at a point other than eye level when standing or when sitting at a desk.
4. Orient the laser so that the beam is not directed toward entry doors or aisles.
5. Minimize specular reflections.
6. Securely mount the laser system on a stable platform to maintain the beam in a fixed position during operation and limit beam traverse during adjustments.
7. Confine primary beams and dangerous reflections to the optical table.
8. Clearly identify beam paths and ensure that they do not cross populated areas or traffic paths.
9. When the beam path is not totally enclosed, locate the laser system so that the beam will be outside the normal eye-level range, which is between 1.2 to 2 meters from the floor. A beam path that exits from a controlled area must be enclosed where ver the beam irradiance exceeds the MPE.
-
9.1 Warning signs : Post at each entrance to the operating area "CAUTION - LOW POWER LASER" signs.
9.2 If the laser has not been labeled by the manufacturer, attach a label on the laser with its classification and relevant warning information. Contact Environmental Health and Safety for assistance.
9.3 Refer to the ANSI Z136.1-2000 for further guidance on control measures for various classifications of lasers.
-
10.1 All Principal Investigators are required to write standard operating procedures (SOP) for all laser operations involving Class 3 and Class 4 lasers detailing alignment, operation and maintenance procedures. The SOP should be posted or attached to the inside surface of the lab door.
10.2 SOP's must include procedures to address when:
-
1. Use of eyewear, shields, and access control are necessary.
2. Two or more Class 3 or Class 4 lasers will be used in the same area by different operators without permanent, intervening barriers.
3. An interlock bypass is installed that does not conform to the conditions of the Laser Safety Manual.
4. A Class 3 or Class 4 laser will be used by non-University personnel; (e.g., contract personnel or visiting colleagues).
5. A laser installation does not include all the required controls specified in this program (e.g., temporary operations).
6. A University of Utah Class 3 or Class 4 laser or laser system is operated off campus.
7. Other hazards may be involved that require an SOP (e.g.., acutely toxic gases, unattended laser operation).
10.4 Labels: A laser classification label must be conspicuously affixed to the laser housing.
10.5 Warning Signs: Each entrance must be posted with an appropriate danger, caution, or warning sign in accordance with ANSI Z136.1-2000.
10.6 Warnings Devices: Entrances to laboratories with a Class 3b or 4 laser shall have a lighted indicator that is fail-safe interlocked with the laser to activate when the laser is energized. The sign must be tested monthly. A written record must be kept of each test in the log book (see section 10.3).
10.7 Safety Interlocks
-
1. Access doors to a controlled laser area in which a Class 3b or a Class 4 laser is being operated must be equipped with safety interlocks to prevent laser operation when the interlock circuit is broken.
2. All protective enclosures that surround laser devices and high-voltage electrical sources must also be equipped with interlocks to prevent operation of the equipment.
3. Interlocks should be tested quarterly to ensure that they are operational . A written record must be kept of each test in the log book (see section 10.3).
4. Interlocks must be designed so that after they are actuated, the capacitor banks, shutters, or power supplies cannot be re-energized except by manually resetting the system.
-
1. There is no laser radiation hazard at the point of entry .
2. The necessary protective devices are worn by the personnel entering the area.
3. An interlock bypass circuit is designed into the interlock control system. This bypass circuit must only be operated from inside the interlocked area. It must delay no more than 15 seconds before shutting down the system.
10.10 Laser laboratories and controlled areas must be designed so that personnel can enter and leave under emergency conditions.
10.11 Lasers must have a master switch with a key or coded access that prevents use once the key has been removed or a code has been entered. The key must not be left in the control panel when the laser is not in use.
10.12 Laser Activation Warning Systems: An alarm, a warning light, or a verbal "countdown" command must be used during activation and start up.
10.13 Lasers must have a permanently attached beam stop or attenuator and emission delays.
10.14 Laser controlled areas shall be established which have limited access, covered windows and doors, and only diffuse reflective material. The facility must be a fully enclosed room or laboratory with floor-to-ceiling walls. Access to the area during laser operation requires the permission of the responsible operator.
10.15 Class 3b and 4 infrared laser beams with a wavelength greater than or equal to 710 nm must be terminated with fire resistant material.
10.16 Securely fasten all mirrors, prisms, beam stops, etc. in the beam path. Ensure that the laser is also securely fastened.
10.17 Circuit breakers must be identified for each laser.
10.18 Beam Enclosure : The entire beam path of Class 3 and Class 4 lasers, including the target area, should be surrounded by an enclosure equipped with interlocks that prevents operation of the laser system unless the enclosure is properly secured. When total enclosure of the laser beam path is not practical, both the non-enclosed laser beam and any strong reflections must be terminated at the end of their useful path using such devices as backstops, shields or beam traps.
10.19 Reflection Control
-
1. Materials that diffusely reflect laser radiation must be used in place of specularly reflective surfaces wherever possible.
2. To minimize personnel exposure, specularly reflecting surfaces that are needed for beam-path control should be enclosed or shielded.
Ultraviolet (UV) and infrared (IR) lasers that emit invisible beams require several additional controls:
-
1. Visual or audible beam-warning devices must be installed in areas where personnel may be exposed to radiation in excess of the MPE. These warning devices must be clearly identified and visible from all areas of potential exposure.
2. Shielding must be installed that will attenuate UV radiation to levels below the MPE for the wavelength being used.
3. Hazardous concentrations of by-products formed by the reaction of intense UV radiation with materials in the area must be controlled.
4. IR beam enclosures and backstops must be fabricated of IR-absorbent material. For Class 4 lasers, the absorbent material must also be fire-resistant.
Controlled laser areas must be surveyed with appropriate measuring devices to locate and identify direct and reflected beams that exceed the MPE; shielding may be required to limit unwanted radiation.
10.22 Direct Viewing
-
1. Personnel must never look directly into any laser beam unless such action is specifically approved by EHS.
2. The primary beam and specular reflections of Class 3 or Class 4 lasers are particularly hazardous. In those cases where it is necessary to directly view a beam from a Class 3 or Class 4 laser, special provisions, such as filters, are mandatory.
3. An SOP must be prepared for operations where the beam of a Class 3 or Class 4 laser must be viewed directly or where it is necessary to work with optical viewers in close proximity to the laser beam.
-
1. High-power laser optical systems must never be aligned by direct beam viewing if the radiant exposure or irradiance exceeds the MPE.
2. Use low-power lasers, diffuse reflectors, image-retaining screens, exposed Polaroid film, and other devices that will minimize eye exposure.
10.24 Optical Viewing Aids
Using optical systems such as cameras, telescopes, microscopes, etc., to view laser beams may increase the eye hazard. Therefore, all collecting optics must incorporate suitable means (such as interlocks, filters, or attenuators) to prevent eye exposures above the MPE.
10.25 Protective Equipment
-
1. Laser protective eye wear shall be worn whenever MPE levels may be exceeded.
2. However, it is good practice to always wear eye protection when lasers are in use.
3. In general, eye wear provides protection over a narrow range of the laser spectrum. Eye wear designed for protection at one wavelength may afford little or no protection at another wavelength.
4. Consult eye wear manufacturers and EHRS for proper selection of protective eye wear (see section 9.1).
5. Laser protective eye wear must be approved by the American National Standards Institute (ANSI) and clearly labeled with optical densities and wavelengths for which protection is afforded. Eye wear must be inspected periodically by the user for pitting and cracking of the attenuating material, and for mechanical integrity and light leaks in the frame.
6. Protection for the skin may be afforded through the use of clothing to cover normally exposed skin areas.
10.26 Unattended Equipment
-
1 . When lasers are to be left unattended, de-energize the power supplies or capacitor banks and remove the keys from power switches or master interlocks to prevent unauthorized activation of the equipment.
2. The operation of unattended lasers is only allowed when a specific SOP has been written and approved by the Principal Investigator.
10.27 Temporary Installations
-
1. Occasionally, it may be necessary to remove protective enclosures or override equipment interlocks or other safety devices for service adjustments, maintenance, special training exercises, etc.
2. In these instances, a temporary controlled laser area must be set up. Specific methods for handling situations of this type must be described in the SOP.
3. Because the area will not have all the standard safety features, the SOP must describe provisions for protecting personnel who could potentially be exposed.
4. When the entire beam path is not fully enclosed, restrict access into the area to persons wearing proper protective equipment. Make sure that all optical paths from the restricted-access area are adequately covered to prevent escape of laser radiation greater than the MPE for the eye.
XI. CONVERTING TO A CLASS 1 ENCLOSED LASER
Any laser or laser system can be converted to a Class 1 enclosed laser by including all of the following controls in the laser system design. These controls will effectively enclose the laser, thus preventing personnel contact with the emitted radiation while permitting unrestricted access into the area.
11.1 Protective Housing
-
1. House the laser system within a protective enclosure to prevent escape of laser radiation above the MPE.
2. The protective housing must prevent personnel access to the laser system during normal operations.
3. Personnel entering the enclosure to perform maintenance or adjustment tasks must be made aware of the higher risks and comply with the control measures for the higher risk laser class.
-
1. Install safety interlocks wherever the protective enclosure can be opened, removed or displaced.
2. When activated, these interlocks must prevent a beam with a radiant energy above the MPE from leaving the laser or laser system .
3. Service adjustments or maintenance work performed on the laser system must not render the interlocks inoperative or cause exposure levels outside the enclosure to exceed the MPE, unless the work is performed in a laser area with limited access and appropriate safeguards, supervision and control.
11.4 Modifications to commercial laser systems must be evaluated. Contact EHS for an evaluation. If the modifications decrease the safety controls, an SOP will be required.
11.5 Attenuated Viewing Windows: Use viewing windows containing a suitable filter material that will attenuate the transmitted laser radiation to levels below the MPE under all conditions of operation.
11.6 Warning Signs and Labels
-
1. Label the enclosure with "CAUTION-ENCLOSED LASER" signs.
2. Attach a label directly to the laser which gives the laser classification in the absence of the enclosure. Make sure that the label can immediately be seen when the enclosure is opened.
XII. CONTROLLING ASSOCIATED HAZARDS
Many chemical and physical hazards other than laser radiation can be found in the laser area that must also be adequately controlled.
-
12.1 Electrical Equipment and Systems
-
1. Always be aware of the high risk of injury and fire in laser operations because of the presence of electrical power sources.
2. The installation, operation, and maintenance of electrical equipment and systems must conform to the standards stated in the National Electric Code. Contact Physical Plant for assistance.
12.2 Lighting
-
1. Adequate lighting is necessary in controlled areas.
2. If lights are extinguished during laser operation, provide control switches in convenient locations or install a radio controlled switch.
3. Luminescent strips should be used to identify table and equipment corners, switch locations, aisles, etc.
4. When natural light is not sufficient for safe egress from a laser area during an electrical power failure, install emergency lighting.
12.3 Ionizing and Non-ionizing Radiation
-
1. A laser operation may involve ionizing radiation that originates from the presence of radioactive materials or the use of electrical power in excess of 15 kV .
2. Microwave and radio frequency (RF) fields may be generated by laser systems or support equipment.
3. Contact EHS at 581-6590 to obtain an evaluation of non ionizing radiation hazards. Hazards associated with ionizing radiation are evaluated by radiological health, 581-6141.
12.4 Hazardous Materials
-
1. Bring into the laser area only those hazardous materials that are needed for the operation.
2. All hazardous materials must be properly used, stored and controlled. Consult Materials Safety Data Sheets, the Chemical Hygiene Plan and EHS for information.
3. Do not allow laser beams and strong reflections to impinge on combustible materials, explosives, highly flammable liquids or gases or substances that decompose into highly toxic products under elevated temperatures, without providing adequate controls.
4. Conduct or sponsor tests that establish the effects of beam interactions with hazardous materials. Test results can be used to determine safe parameters for laser operation.
12.5 Dyes and Solutions
- 1. All dyes must be treated as hazardous chemicals. Most solvents suitable for dye solutions are flammable and toxic by inhalation and/or skin absorption.
2. Obtain Material Safety Data Sheets from the supplier for all dyes and solvents.
3. Use and store all dyes and solvents in accordance with the Laboratory Chemical Hygiene Plan.
4. Prepare/handle dye-solutions inside a chemical fume hood.
5. Wear a lab coat, eye protection and gloves. Refer to the EHS website for assistance.
6. Pressure-test all dye laser components before using dye solutions. Pay particular attention to tubing connections.
7. Install spill pans under pumps and reservoirs.
8. Be alert to contaminated parts.
9. Keep dye-mixing areas clean.
September 2001