MASSACHUSETTS INSTITUTE OF TECHNOLOGY

RADIATION PROTECTION PROGRAM

LASER SAFETY PROGRAM

Eighth Edition (interim) April 2008 MIT RADIATION PROTECTION COMMITTEE

PREFACE: The MIT Radiation Protection Committee (RPC) is responsible for the establishment and continuing review of an adequate radiation protection program at the Institute and its off-campus sites. The Committee is also responsible for the Institute's compliance with radiation protection regulations promulgated by state, Federal, and local agencies for both ionizing and non-ionizing radiation. The MIT Radiation Protection Program (RPP) administers the radiation protection program through a variety of services provided to the MIT community. All uses of radioactive material, radiation producing equipment, RF generators, and lasers must be registered with the MIT Radiation Protection Program. Departmental, Laboratory, or Center (DLC) EHS Coordinators must contact the Radiation Protection Program to arrange laser registrations, safety inspections, and laser safety training with the responsible RPP staff member. Project Supervisors, typically members of the faculty or senior scientists, are ultimately responsible for compliance with all requirements of this laser safety program. Specific programmatic elements that the project supervisor must ensure include directing that all laser workers are trained and registered by RPP, that all laser systems are registered and inspected by RPP, and that all safety requirements, especially the use of laser protective eyewear, are followed at all times. The RPC maintains the authority for assurance of laser safety for personnel at MIT. In that capacity, the RPC may vote to revoke or modify a projects registration to use Class 3b or Class 4 lasers. Mitchell Galanek, the MIT Radiation Protection Officer, will serve as the MIT Laser Safety Officer. Please call the Radiation Protection Program at 617-452-3477 with any questions concerning the Laser Safety Program. This document is comprised of two sections the first covers specific requirements of the Laser Safety Program and the second section covers some general recommended practices and training topics

Please read this article first!!!!! Here is why laser safety is important! "Smart people learn from their mistakes. Wise people learn from other people's mistakes. Unknown author. (Taken from Laser Focus, August 1977) Accident Victim's View Because laser injuries to eyes are rare, workers tend to discount the importance of safety precautions. The following dramatic account by Dr. C. David Becker, a victim of such an accident earlier this year, was prepared in the hope that his experience may increase vigilance among his colleagues. The necessity for safety precautions with high power lasers was forcibly brought home to me last January when I was partially blinded by a reflection from a relatively weak neodymium-YAG laser beam. Retinal damage resulted from a 6 millijoule, 10 nanosecond pulse of invisible 1064 nanometer radiation. I was not wearing protective goggles at the time, although they were available in the laboratory. As any experienced laser researcher knows, goggles not only cause tunnel vision and become fogged, they become very uncomfortable after several hours in the laboratory. When the beam struck my eye I heard a distinct popping sound, caused by a laser-induced explosion at the back of my eyeball. My vision was obscured almost immediately by streams of blood floating in the vitreous humor, and by what appeared to be particulate matter suspended in the vitreous humor. It was like viewing the world through a round fishbowl full of glycerol into which a quart of blood and a handful of black pepper have been partially mixed. There was local pain within a few minutes of the accident, but it did not become excruciating. The most immediate response after such an accident is horror. As a Vietnam War Veteran, I have seen several terrible scenes of human carnage, but none affected me more than viewing the world through my bloodfilled eyeball. In the aftermath of the accident I went into shock, as is typical in personal injury accidents.

As it turns out, my injury was severe but not nearly as bad as it might have been. I was not looking directly at the prism from which the beam had been reflected, so the retinal damage is not in the fovea. The beam struck my retina between the fovea and optic nerve, missing the optic nerve by about three millimeters. Had the focused beam struck the fovea, I would have sustained a blind spot in the center of my field of vision. Had it struck the optic nerve, I probably would have lost the sight of that eye. The beam did strike so close to the optic nerve, however, that it severed nerve-fiber bundles radiating from the optic nerve. This has resulted in a crescent-shaped blind spot many times the size of the lesion. The diagram is a Goldman-Fields scan of the damaged eye, indicating the sightless portions of my field of view four months after the accident. The small blind spot at the top exists for no discernable reason; the lateral blind spot is the optic nerve blind spot. The effect of the large blind area is much like having a finger placed over one's field of vision. Also I still have numerous floating objects in the field of view of my damaged eye, although the blood streamers have disappeared. These "floaters" are more a daily hinderance than the blind areas, because the brain tries to integrate out the blind area when the when the undamaged eye is open. There is also recurrent pain in the eye, especially when I have been reading too long or when I get tired. The moral of all this is to be careful and to wear protective goggles when using high power lasers. The temporary discomfort is far less than the permanent discomfort of eye damage. The type of reflected beam which injured me also is produced by the polarizers in q switches, by intracavity diffraction gratings, and by all beamsplitters or polarizers in optical chains.

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Table of Contents Part One - MIT Radiation Protection Program Laser Safety Program Requirements 3 I. INTRODUCTION 5 II. Responsibilities 5

A. Radiation Protection Program B. Departments, Laboratories and Centers (DLCs)

C. EHS Coordinator D. Principle Investigator/Supervisor (PI/S)

E. EHS Representative: F. Laser Users

III. Laser Registration 8 IV. Laser Safety Training and User Registration 9 V. Laser Incidents 9 VI. Laser Classifications 9 VII. Laser Facility - Design Requirements 11 VIII. Laser Facility - Safe Operation Requirements 13 Part Two - Laser Safety Training Supplement and Recommendations 15 IX. INTRODUCTION 15 X LASER HAZARDS 15 XI. General Hazard Controls 16 XII. Laser Classifications 17 XIII. Eye Protection and Maximum Permissible Exposures 18

1. Retinal Damage 2. Lens Damage 3. Corneal Damage 4. Other Ocular Damage 5. Maximum Permissible Exposure (MPE) 6. Protective Eyewear

XIV. Skin Exposure and Maximum Permissible Exposures 22 XV. General Safety Procedures 21 XVI. Recommended Laser Safety Controls 21

A. Class 1 Controls B. Class 2 Controls C. Class 1M, 2M, and 3R Controls D. Class 3b Controls E. Class 4 Controls F. General Controls for Experimental Procedures G. Controls During Beam Alignment

Appendix A Registration of Laser Systems 27 Appendix B Laser Worker Registration 29 Appendix C Laser Postings 30 Appendix D MIT Policy for Laser Eye Exams 31 Appendix E Definitions 34 Appendix F Specific Precautions for Beam Alignment 36 Appendix G List of Laser Protective Eyewear Manufacturers and Vendors 39

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Part One - LASER SAFETY PROGRAM REQUIREMENTS II. INTRODUCTION

The safe use of laser systems depends upon the basic principles of safety, which are recognition, evaluation, and control of potential hazards. This program will review laser operations, the associated potential hazards, responsibilities of the laser user community, and the services provided by the Radiation Protection Program (RPP) to aid in the safe use of laser radiation. All persons installing, operating, using, maintaining, repairing, or servicing lasers or laser systems at MIT shall do so in accordance with the requirements set forth in the most recent published version of the publication published by ANSI entitled American National Standards for Safe Use of Lasers and known and referred to as ANSI Z 136.1 2007 Table 1. Requirements by Laser Classification (adapted from ANSI Z136.1 2007)

Class Procedural and Administrative

Controls Training Medical Surveillance

1 Not Required Not Required Not Required 1M Not Required * Not Required * Not Required 2 Not Required Not Required Not Required

2M Not Required * Not Required * Not Required 3R Not Required Not Required Not Required 3b Required Required Suggested** 4 Required Required Suggested**

* If collecting optics is used or the system is on and left unattended in a public space then these items are required. ** Anyone working with, or in the vicinity of, a Class 3b or 4 open beam laser system a baseline laser eye exam is suggested. Enclosed laser systems the baseline eye exam is not required.

II. Responsibilities

A. Radiation Protection Program

Detailed information on the control of laser radiation hazards is available from the Radiation Protection Program, 2-3477, Room N52-496. Some of the more important elements are outlined in this manual. RPP will provide services to assist the Principle Investigators/Supervisors (PI/S), DLC-EHS Coordinators, and EHS laboratory Representatives in maintaining a comprehensive