VII(b). Radiation Safety - Lasers
A. Purpose And Summary
This Chapter describes requirements for personnel protection from laser radiation and other associated hazards. These requirements are designed to comply with the Massachusetts Department of Public Health (DPH) Code 105 CMR 121.000, "Rules and Regulations Relative to the Use of Laser Devices or Equipment to Control the Hazards of Laser Rays and Beams". A copy of these regulations is available at the Environmental Health and Safety Office.
This document delineates the requirements for registration and safe use of high power lasers and laser systems. All operations or research involving the use of lasers must be conducted in such a manner as to ensure that personnel exposure to laser radiation is below the maximum levels specified in 105 CMR 121.600. Further, all operations involving the use of high power lasers shall be planned and executed using the recommendations of the American National Standards Institute Z136.1 - 2007, "Standard for the Safe Use of Lasers". Many of those recommendations are incorporated into this document. ANSI Z136.1 is available in the Environmental Health and Safety Office.
The following is a summary of requirements for laser use.
Laser Requirement Summary
|Registered with RSO||2||3a||3b||4|
|Laser Safety Training||3a||3b||4|
|Laser Safe Operating Protocol||3b*||4|
*If invisible to the eye, and if a cw laser, with visible beams > 15mW of power.
B. Laser Classification
Lasers are classified according to the definitions of Section 3.3 of ANSI Z136.1. Classification and labeling of commercially purchased lasers is the responsibility of the manufacturer. In addition to meeting the general requirements of this Chapter, lasers must meet specific requirements based on laser class. Only lasers fabricated on-site would require classification by the Investigator, which requires approval of the Radiation Safety Officer.
Laser classification and entry controls are summarized below. Details of laser classification and examples of typical laser classifications as described in ANSI Z136.1 are included, in abbreviated form, in Appendix VII(b)-A.
Class 1 denotes exempt lasers or laser systems that cannot, under normal operating conditions, produce a hazard. Equipment such as laser printers that completely enclose the laser and laser beam are normally specified as Class 1.
Class 1 lasers must be labeled, but are exempt from other requirements.
Class 2 denotes low power visible‑radiation lasers or laser systems. Visible cw HeNe lasers above Class 1, but not exceeding 1mW (milliwatt) radiant power, are common examples of this class. Because of the normal human aversion or blink response, these lasers normally do not present a hazard. Class 2 lasers may present a hazard if viewed directly for extended periods of time (like many conventional light sources).
Class 2 lasers must be labeled and registered with the Radiation Safety Officer, but are exempt from other requirements. The warning label or sign shall caution users to avoid staring into the beam or directing the beam toward the eye of individuals, and shall be placed on or near the laser in a conspicuous location.
Class 3a denotes lasers or laser 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. Visible cw HeNe lasers above 1mW but not exceeding 5mW radiant power are examples of this class.
Class 3a lasers must be operated in a location where access to the beam can be controlled. The potential for viewing of the direct or specularly reflected beam must be minimized. The operator of the laser shall inform personnel entering the area of the presence of the laser beam and the precautions they need to follow.
Class 3b denotes lasers or laser systems that can produce a hazard if viewed directly. This includes intra-beam viewing or specular reflections. Except for the higher power Class 3b lasers, this class laser will not produce hazardous diffuse reflections. Visible cw HeNe lasers above 5mW but not exceeding 500mW radiant power are examples of this class.
Class 3b lasers must be used in areas where entry by unauthorized personnel can be controlled. Entry into the area of personnel untrained in laser safety may be permitted by the laser operator if they are instructed as to safety requirements and are provided with protective eyewear, if required.
Class 4 denotes lasers or laser systems that can produce a hazard not only from direct or specular reflections, but also from a diffuse reflection. In addition, such lasers may produce fire and skin hazards.
Class 4 lasers must be operated by authorized users in areas dedicated to their use. Failsafe interlocks must be used to prevent unexpected entry into the controlled area, and access shall be limited by the laser operator to persons who have been instructed as to safety procedures and who are wearing proper laser protection eyewear (if required by written procedures) when the laser is capable of emission. Authorized operators are responsible for providing information and safety protection to untrained personnel who may enter the laser controlled area as visitors.
For pulsed systems, interlocks shall be designed so as to prevent firing of the laser, by dumping the stored energy into a dummy load. For continuous wave lasers, the interlocks shall turn off the power supply or interrupt the beam by means of shutters.
Manufacturer classifications are based on the level of laser radiation accessible during intended operation of the laser. The hazard may be greater, and therefore require additional controls, when maintenance or service is being performed.
C. Responsibilities Of Laser Investigators
Investigators using lasers are responsible for assuring their safe use in their area or lab. Specific responsibilities include:
- Complying with and enforcing the safety requirements prescribed in this Chapter.
- Reporting all proposed purchases of Class 2, 3a, 3b, and 4 lasers to the Radiation Safety Committee by submitting a Registration form (Appendix VII(b)-B).
- Registering all existing Class 2, 3a, 3b, and 4 lasers by submitting a Registration form (Appendix VII(b)-B).
- Providing a Laser Safe Operating Protocol (see Appendix VII(b)-C) to the Radiation Safety Committee for approval for all Class 3b and 4 lasers.
- Assuring that all users and other personnel are properly instructed in safe procedures for working with all lasers in his/her charge (see Appendix VII(b)-D).
- Assuring that all required protective equipment is used during laser work.
- Reviewing in advance all lab procedures to be used by laser users in carrying out research work involving laser radiation for possibility of laser exposure, and associated non-beam hazards.
- Assuring the integrity of associated equipment such as vacuum systems, cryogenic systems, pressure vessels or other similar equipment to be used in conjunction with a laser.
- Assure that all laser system safety interlocks, warning lights, etc. are functioning.
- Posting warning signs and otherwise controlling laser hazards for which the Investigator is responsible.
- Maintaining control of visitors.
D. Responsibilities Of Laser Users
The individual user is responsible for:
- Using only Investigator approved techniques and procedures in operations involving the use of lasers.
- Wearing prescribed protective glasses and any other required protective clothing or equipment.
- Meeting all applicable requirements of this Chapter including those of training and medical surveillance before operating any laser.
- Maintaining a current "Authorized Laser User Certification" (see Section J).
E. Responsibilities Of The Radiation Safety Officer
- Reviewing laser facility use procedures to assure safe use.
- Maintaining a current laser inventory to comply with the DPH registration requirement.
- Performing laser safety surveys for Class 3b and 4 lasers at least annually.
- Maintaining all required records for DPH inspection.
- Investigating all accidents or incidents involving laser radiation to determine the cause(s) and to recommend corrective action to the Radiation Safety Committee.
- Providing the Radiation Safety Committee and Investigators with advice and assistance on matters pertaining to the safe use of lasers.
F. Responsibilities Of Radiation Safety Committee
- Establishing policies and procedures on the safe use of lasers.
- Reviewing the laser safety aspects of the use of all lasers on campus.
- Review reports of accidents or incidents involving lasers and assure that appropriate corrective action is taken to prevent re-occurrence.
G. Laser Registration
The Massachusetts Public Health Department, Radiation Control Section, requires that all lasers be registered with the department. The law further requires that all new purchases of lasers be registered prior to receipt. In order to comply with this law, the Radiation Safety Officer will maintain a laser inventory.
Prior to purchase of a Class 2, 3a, 3b, or 4 laser, and for existing lasers, a Registration form (Appendix VII(b)-B) must be submitted.
H. Laser Safe Operating Protocol
A Radiation Safety Committee approved Laser Safe Operating Protocol (LSOP) is required for all Class 3b and 4 lasers. However, the Radiation Safety Committee may recommend or require a LSOP for any laser or laser application where it is deemed necessary for ensuring adequate safety controls.
LSOPs are prepared by the Investigator. The LSOP shall include all information outlined in Appendix VII(b)-C and shall receive Radiation Safety Committee approval before the laser is operated. As with other Radiation Protocols, LSOPs are reviewed and approved annually.
I. General Safety Requirements
- Each class 3a, 3b, and 4 laser shall receive a preliminary safety review and approval by the Radiation Safety Officer prior to acquisition or fabrication of the laser. These lasers also shall receive a final safety review and approval by the Radiation Safety Officer prior to initial use of the laser. The final review shall cover user qualifications, safe operations including electrical safety, area controls, and written procedures if required.
- Each laser and laser application shall meet the safety standards of ANSI Z136.1 or an equivalent level of safety approved by the Radiation Safety Committee.
- Each Class 3a, 3b, or 4 lasers shall be used in a controlled area in order to restrict access of unauthorized personnel. The level of control depends on the laser class.
J. Laser Safety Training
All users of Class 2, 3a, 3b, and 4 lasers shall receive training by the Investigator and read "Laser Safety Training" (see Appendix VII(b)-D). All users of Classes 3a, 3b, and 4 lasers shall be re-certified in Laser Safety at intervals not to exceed two years.
Upon completion of training, the Investigator and User must complete an "Authorized Laser User Certification" form (Appendix VII(b)-D). A copy of the Certification must be sent to the Radiation Safety Officer.
K. Laser Medical Surveillance
All Investigators and Users who are routinely engaged in work where they may be exposed to laser radiation from a class 3b or 4 laser must participate in the laser medical surveillance program.
The purpose of laser medical surveillance is two-fold. The first purpose is to establish a baseline of ocular conditions before exposure to laser radiation. The second purpose is to detect and document, as early as possible, ocular damage in the event of a suspected exposure incident. Both purposes serve to assess the effectiveness of control measures and to promptly institute appropriate therapeutic measures.
Laser medical surveillance includes a preliminary baseline eye exam. Additional eye exams are required immediately in the event of exposure or suspected exposure to laser radiation above the Maximum Permissible Exposure (MPE) established in 105 CMR 121.600 (pulse and wavelength dependent). An eye exam may be required upon termination of laser work or upon termination of employment at the College.
Investigators should contact the Environmental Health and Safety Office to schedule baseline eye exams, and report suspected exposures above the MPE.
L. Laser Warning Signs
Laser warning signs must meet the standards of ANSI Z136.1. Class 1 lasers do not require a sign. The word CAUTION shall be used with all Class 2 and Class 3a lasers. The word DANGER shall be used with all Class 3b and Class 4 lasers. Signs, including the appropriate precautionary statements detailed in ANSI Z136.1, must be described in the LSOP.
All warning signs and labels shall be displayed conspicuously in locations where they best serve to warn individuals of potential safety hazards. Normally, warning signs are posted at entryways (e.g. on doors) to laser controlled areas.
Warning labels are affixed to the lasers in a conspicuous location. Laser warning signs should be removed by the laser Investigator if the laser has been removed from the room or area.
M. Safe Laser Practices
The following control measures are recommended as a guide to safe laser use. If any of these control measures cannot be accomplished, the LSOP must describe alternative controls to provide comparable protection. These practices are taken from ANSI Z136.1. Refer to that document for additional details.
The purpose of controls is to reduce the possibility of exposure to the eye and skin to hazardous laser radiation and to control other hazards associated with operation and maintenance of laser devices.
Engineering controls (physical features incorporated into the design or installation of the laser system) are the preferred method of control. If engineering controls are not feasible, then administrative and procedural controls and personal protective equipment should be used.
- Protective housings should be provided for all classes of lasers.
- Protective housings that enclose Class 3b or 4 lasers should have an interlock system that is activated when the protective housing is opened.
- Enclosure of the laser equipment or beam path is the preferred method of control.
- Service access panels intended to be removed by service personnel only and which permit direct access to laser radiation associated with Class 3b or 4 lasers should either be interlocked or require a tool for removal and have an appropriate warning sign.
- Class 3b lasers should be provided with a master switch. Class 4 lasers must have a master switch. The master switch should be operated with a key or coded access (e.g., computer authorization password).
- Lasers with viewing portals should have means, (e.g., interlock, filter, attenuators), to maintain laser radiation below the MPE.
- The laser should be set up so that the beam path is not at normal eye level, (i.e., so it is below 4.5 feet and above 6.5 feet).
- All collecting optics intended for viewing use should incorporate means to maintain laser radiation transmitted through the collecting options to levels below the MPE.
- Class 3b lasers should be provided with a remote interlock connector. Class 4 lasers must be provided with a remote interlock connector. The interlock connector provides electrical connection to an emergency master disconnect or to a room, or area interlock.
- Class 3b lasers should be provided with a permanently attached beam stop attenuator. A Class 4 laser must be provided with such an attenuator.
- An alarm, warning light, or verbal countdown command should be used with a Class 3 laser and must be used with a Class 4 laser to signal activation. For Class 4 lasers there must be an emission delay to allow action to be taken to avoid exposure.
- When possible, Class 4 lasers should be fired and monitored from a remote position.
Administrative and Procedural Controls
- In applications using Class 3b or 4 lasers with unenclosed beam paths, the Nominal Hazard Zone (NHZ: space within which the level of direct, reflected, or scattered radiation during operation exceeds the applicable MPE) must be established. A laser-controlled area must be established in this zone, and appropriate control measures established.
- Class 3a, 3b and 4 lasers must only be operated and maintained by authorized Investigators and Users.
- LSOPs are required for all Class 3b, and 4 lasers.
- A RSO safety review is required for all Class 3a, 3b, and 4 lasers.
- User Training is required for all Class 2, 3a, 3b, and 4 lasers.
Recommended Work Area Controls
Entry controls must prevent unauthorized people from being present when the laser is energized or about to be energized.
- The illumination in the area should be as bright as practicable in order to constrict the eye pupils of users.
- The potential for specular reflections should be minimized by shields and by removal of all unnecessary shiny surfaces.
- Windows to hallways or other outside areas should be provided with adequate shades or covers.
- The main beams and reflected beams should be terminated by material that is non-specular reflective and fireproof. This is required for any accessible laser for which the MPE could be exceeded.
- An active laser should never be left unattended unless it is part of a controlled environment.
- Good housekeeping should be practiced to ensure that no device, tool, or other reflective material is left in the beam.
Recommended Laser Use Controls
The manufacturer's recommendations for safe laser use must be followed unless alternative methods are described and approved in the LSOP.
- Avoid looking into the primary beam at all times.
- Do not aim the laser with the eye; direct reflections can cause retinal damage.
- Avoid looking at the pump source.
- Clear all personnel from the anticipated path of the beam.
- Before operating the laser, warn all personnel and visitors of the potential hazard, and ensure all safety measures are satisfied.
- Be especially cautious around lasers that operate at invisible light frequencies.
- Do not wear bright, reflective jewelry or other objects.
Laser Protective Equipment
Normally, all persons who work in areas where there is radiation from Class 3b or Class 4 lasers must wear approved laser eyewear if the potential exists for exposure in excess of the MPE. Exceptions may be approved if wearing protective eyewear produces a greater safety hazard than when it is not worn. Exceptions shall be described in the LSOP and approved by Radiation Safety Committee.
The Radiation Safety Officer shall review and approve protective eyewear to assure that it is appropriate for the use for which it is intended. The eyewear to be used will depend on the wavelength(s) and intensity of the accessible radiation. Keep in mind:
- No matter how good the glasses, no protection is provided unless worn.
- All safety glass may shatter, and all plastic lenses may melt when maximum irradiance or radiant exposure for the particular lens is exceeded.
- Laser safety glasses may not provide eye protection with other than the laser for which they are specified, unless the frequency produced is the same and power output is not greater.
In some cases, other protective equipment, such as clothing to protect the skin, may be required. Such requirements must be addressed in LSOP.
N. Associated (Non-Beam) Laser Hazards
Depending on the type of laser used, associated hazards other than those from beam radiation may be involved. Such hazards, if they exist, must be addressed in the LSOP.
- Vaporized target material: contaminants may include carbon monoxide, ozone, lead, mercury, and other metals.
- Gases from flowing gas lasers or byproducts of laser reactions such as fluorine, hydrogen‑cyanide, and many others.
- Gases or vapors from cryogenic coolants.
Chemicals, including dyes and solvents, from certain dye lasers have been shown to be carcinogenic, toxic, or otherwise hazardous.
Cryogenic liquids, such as liquid nitrogen or hydrogen, may cause burns.
The potential for electrical shock is present in most laser systems. Pulsed lasers utilize capacitor banks for energy storage and cw lasers generally have high voltage DC or RF electrical power supplies.
The potential exists for explosions at capacitor banks or optical pump systems during the operation of some high power lasers. Explosive reactions of chemical laser reactants or other gases used within the laser laboratory could cause damage to equipment or injury to personnel.
The use of jewelry (watches, rings etc.) is often an overlooked source of exposure to a beam reflected by a mirror-like surface.
Either direct or reflected UV radiation from flash lamps and cw laser discharge tubes may cause eye injury. Usually, UV radiation is a problem only when quartz tubing or windows are used.
Visible Radiation (non-laser)
High luminance radiation emitted from unshielded pump lamps may cause eye injury. Potentially hazardous X-rays may be generated from high voltage (over 15kV) power supply tubes.