LASER SAFETY MANUAL

Radiation Safety Office

Indiana University - Bloomington

1.0 INTRODUCTION

It is the policy of Indiana University – Bloomington (IUB) to support the use of lasers for purposes of research and teaching. At the same time, the university is committed to ensuring the safety of students, staff, and faculty who work with, or in the vicinity of, these devices. Toward this end, requirements for the safe use of lasers have been adopted as part of a campus laser safety program. These requirements are derived from the American National Standard for the Safe Use of Lasers (ANSI Z136.1), which should be consulted directly for more detailed or specific information (a copy of the ANSI standard is available in the Radiation Safety Office, Jordan Hall, room 071 or can be obtained at: http://ansi.org/).

This manual describes the various components of the IUB laser safety program and the specific requirements that must be observed by all users of Class 3b or 4 lasers on the IUB campus. In addition, general information on lasers and their associated hazards is included as a means of providing a portion of the training required for laser users (see Appendix A). For questions regarding laser safety, contact the Laser Safety Officer at 5-3230.

2.0 RESPONSIBILITIES

In order to ensure the implementation of the requirements of the campus laser safety program, the following responsibilities are designated:

2.1 Laser Safety Officer

A staff professional within the campus Radiation Safety Office shall be designated as the Laser Safety Officer and shall:

· Maintain an inventory of all Class 3b and 4 lasers at IUB.

· Review and communicate changes in laser safety requirements through periodic updates to the Laser Safety Manual.

· Provide assistance in evaluating and controlling laser hazards.

· Conduct periodic audits to ensure compliance with laser safety requirements.

2.2 Department Chair

The chair of each academic department is responsible for the safety of all individuals working in the department’s facilities. The chair fulfills this responsibility by ensuring that all departmental faculty members understand and take seriously their roles in implementing campus safety programs.

2.3 Principal Investigator

Each Principal Investigator whose research involves the use of a Class 3b or 4 laser shall:

· Register each laser with the Laser Safety Officer by completing and submitting Form LS-1 (see Appendix C).

· Ensure that the laser is operated safely and in accordance with all university requirements as detailed in the Laser Safety Manual.

· Develop, for each laser, a written standard operating procedure that incorporates appropriate safety considerations and requirements.

· Ensure that each laser user has completed the required baseline eye exam (see Form LS-2 in Appendix C) and read the Laser Safety Manual before beginning use of the laser.

· Provide (and require the use of) appropriate eye protection for all laser users.

· Provide specific safety training, appropriate to the use of the laser, to each user.

2.4 Laser User

Each individual who operates a Class 3b or 4 laser shall:

· Complete the required baseline eye exam (see Form LS-2 in Appendix C), read the Laser Safety Manual, and complete specific training provided by the Principal Investigator before operating the laser.

· Operate the laser safely and in accordance with all requirements contained in the Laser Safety Manual.

· Notify the Laser Safety Officer of any conditions that could compromise safety or compliance with university requirements.

3.0 TRAINING

Prior to use of a Class 3b or 4 laser at Indiana University – Bloomington, an individual must complete sufficient and appropriate training to ensure the safe use of this device. This manual, including the Laser Hazard Training Guide contained as Appendix A, form an essential component of this training. However, additional training specific to the particular laser and use must be provided by the Principal Investigator.

4.0 MEDICAL SURVEILLANCE

Each individual who wishes to use a Class 3b or 4 laser at Indiana University, must first complete a baseline eye examination through the IU School of Optometry (call 5-8436 for an appointment and take a completed LS-2 form to the exam).

The examination will include:

· Ocular medical history, including hyperphotosensitive conditions

· Visual acuity 20/20 (6/6 each eye far, Jaeger 1+ near with corrections)

· Macular function (Amsler grid or similar pattern)

· Color vision (Ishihara or similar test)

In the event of a laser exposure incident that involves the eye, the laser user must immediately notify the Laser Safety Officer at (5-3230) and arrange for a follow-up eye examination. For exposure incidents that involve the skin or for any exposure incident that occurs after-hours, the laser user should contact (and arrange for transport to) Prompt Care.

5.0 LASER HAZARD CONTROL MEASURES

Indiana University – Bloomington has adopted as requirements the recommendations of ANSI Z136.1 for hazard control measures for lasers. The ANSI standard specifies various engineering controls, administrative and procedural controls, and protective equipment for lasers and laser systems according to their hazard class. The intent of these controls and equipment is to ensure that the exposure of individuals who work with lasers is at or below the Maximum Permissible Exposure (MPE). Engineering controls typically involve certain physical features or operating characteristics that can be designed into the laser system to ensure safety. Administrative and procedural controls include a wide range of measures such as the development and observance of standard operating procedures and requirements for user training and education. Protective equipment includes both personal protective equipment such as protective eyewear and protective barriers or curtains that surround the laser system. The ANSI standard strongly recommends that engineering control measures be given first priority and that administrative and procedural controls as well as use of protective equipment be employed only as supplemental measures when engineering controls are either impractical or inadequate. A summary of the required control measures is given below (see also Tables 3 and 4 in Appendix B).

5.1 Engineering Controls - All Classes

A protective housing with appropriate warning label shall be provided and utilized for all lasers except for certain applications, such as in research and development, where operation of the laser without a housing is necessary.

5.2 Engineering Controls - Class 3b and 4

1. A safety interlock shall be provided for any portion of the protective housing which, by design, can be removed during normal operation.

2. Service access panels permitting direct access to laser radiation shall be interlocked or shall require a tool for removal.

3. A key-actuated master interlock shall be provided for system operation.

4. All viewing portals and display screens included as an integral part of the laser system shall incorporate a suitable means (such as interlocks, filters, attenuators) to maintain the laser radiation for all operating conditions at or below the MPE.

5. The beam should be enclosed to the extent possible for the specific application. Where this is not possible, a Nominal Hazard Zone (NMZ) with appropriate control measures shall be established and observed.

6. A permanently attached beam stop, capable of reducing the laser radiation to levels below the applicable (MPE) shall be provided at the laser exit port.

7. A warning light or alarm shall indicate laser start-up and operation.

5.3 Additional Engineering Controls - Class 4

1. In situations where the beam is not completely enclosed, operation shall occur only in a light-tight area with interlocked entrances, remote controls, and "panic button" for emergency deactivation of the system.

2. Beam stops shall consist of diffuse-reflecting, fire resistant materials.

3. Adequate ventilation of the operation area shall be provided.

5.4 Administrative/Procedural Controls - Class 3b and 4

1. Written standard procedures for operation, service, and maintenance of the laser system shall be developed and observed.

2. All individuals who will operate or service the laser system shall be provided with training which includes information on the potential hazards of the system and the appropriate controls to be utilized in minimizing these hazards.

3. All entrances to areas with laser systems shall be posted with appropriate warning signs (see Section 6.0 of this manual)

5.5 Protective Equipment

1. Eye protection devices which are specifically designed for protection against radiation from Class 3b and 4 lasers shall be provided to and worn by laser users when engineering or other procedural and administrative controls are inadequate to eliminate potential exposure in excess of the applicable MPE (see Table 5 in the Appendix B for selection criteria).

2. Facility windows that are located within the NHZ of a Class 3b or 4 laser shall be provided with appropriate filter, blocking barrier, or screen that reduces any transmitted laser radiation to levels below the applicable MPE level.

3. A barrier, screen, or curtain that can block or filter the laser beam at the entryway to the NHZ shall be used to prevent laser light from exiting the area at levels above the applicable MPE.

6.0 WARNING SIGNS

Each entrance to an IUB facility that contains a Class 3b or 4 laser shall be posted with an appropriate laser warning sign. ANSI Z136.1 recommends that signs and labels conform to a standard design, format, and content. In general, the following information should be included:

1. At position 1 above the tail of the sunburst, special precautionary instructions or protective action such as: Laser Protective Eyewear Required; Invisible Laser Radiation; Knock Before Entering; Do Not Enter When Light is On; Restricted Area

Alternatively, position 1 above the tail of the sunburst can indicated special precautionary instructions or protective actions required by the reader such as:

A. For Class 2 and Class 3a lasers and laser systems where the accessible irradiance does not exceed the appropriate MPE based upon a 0.25 second exposure; Laser Radiation - Do not Stare into Beam or View with Optical Instruments.

B. For all other Class 3a lasers and laser systems; Laser Radiation - Avoid Direct Eye Exposure.

C. For all Class 3b lasers and laser systems; Laser Radiation - Avoid Direct Exposure to Beam.

D. For Class 4 lasers and laser systems; Laser Radiation - Avoid Eye or Skin Exposure to Direct or Scattered Radiation.

2. At position 2 below the tail of the sunburst, the type of laser (Ruby, Helium-Neon, Nd -YAG, etc.), or the emitted wavelength, pulse duration (if appropriate), and maximum output.

3. At position 3, the class of the laser or laser system.

Figure 1. Sample Warning Sign for Certain Class 3a Lasers

and for Class 3b and Class 4 Lasers

APPENDICES

TO

LASER SAFETY MANUAL

APPENDIX A

LASER HAZARD TRAINING GUIDE

1.0 LASER FUNDAMENTALS

The term "laser" is an acronym for "Light Amplification by Stimulated Emission of Radiation." A laser is a device that utilizes the natural oscillations of atoms or molecules between energy levels for generating electromagnetic radiation which is coherent, parallel beam, and monochromatic. The laser consists of three basic components: (a) the lasing medium - which can be solid, liquid (dye), gas, or semiconductor; (b) the optical cavity - which contains the medium to be excited between mirrors which redirect the produced photons back along the same parallel path; and (c) the pumping system - which uses photons from another source to transfer energy to the medium.

Figure 1. Laser Components

2.0 TYPES AND CHARACTERISTICS OF LASERS

Lasers can be classified by a number of physical and operational characteristics including the lasing medium, wavelength, temporal mode of operation, and beam power (see Tables 1 and 2 in the Appendix B).

2.1 Lasing Medium

The lasing medium is the characteristic most often used to designate the laser type. Carbon dioxide, helium-neon, xenon, dyes, ruby, and neodymium-YAG are examples of materials widely used as lasing mediums. The particular material selected as the lasing medium will, in turn, determine the laser's wavelength.

2.2 Wavelength

The absorption and transmission characteristics of a given laser are determined largely by its wavelength. Laser wavelengths typically range from 10^-3 to 10³ micrometers with this range being divided into three general regions: (1) ultraviolet; (2) ocular focus; or (3) infrared. The ocular focus region, which contains the visible portion of the spectrum, extends from 0.4 to 1.4 micrometers.

Figure 2. Laser Spectral Region

2.3 Temporal Mode of Operation

Lasers are also classified by the rate at which they emit radiation over time. In general, laser radiation is emitted in one of two time modes: (1) continuous wave; or (2) pulsed. Continuous wave lasers produce a steady stream of photons with a beam power which remains constant over time. Pulsed lasers emit "bursts" or pulses of photons with each pulse being less than 0.25 seconds in length. The pulse duration of most pulsed lasers ranges from milliseconds to picoseconds.

2.4 Beam Power

One of the most important characteristics of the laser in determining its hazard potential is beam power or energy. For continuous wave lasers, the beam is characterized by its power density (W/cm²), which is a function of beam diameter and the laser's output power. Pulsed lasers are characterized by their energy density (J/cm²), which is dependent upon the beam diameter and the energy of an individual pulse.

3.0 LASER REFLECTIONS

Laser beams are reflected to some extent from any surface contacted. If the reflected rays remain parallel (i.e., the angle of reflection equals the angle of incidence), the reflection is called "specular". If the reflected rays are randomly scattered, the reflection is called "diffuse". Specular reflections are produced by highly polished, mirror-like surfaces whereas diffuse reflections result from rough, irregular surfaces (however, specular reflections can also be produced by rough surfaces when the size of the surface irregularities is less than the wavelength of the incident radiation). The distinction between a specular reflection and a diffuse reflection is not always clearly defined. Except for reflections from precisely constructed optical mirrors, all beams are to some extent divergent. In general, however, the rougher the reflecting surface, the greater will be the divergence (or diffuseness) of the reflected beam and the less will be its corresponding hazard potential.

Figure 3. Types of Laser Reflections

4.0 LASER HAZARDS

The hazards that are associated with the use of lasers can be divided broadly into (1) those present from the "direct" effects of the laser beam upon human tissue; and (2) those posed "indirectly" by the laser beam or by the physical, mechanical, chemical, or electrical aspects of the laser system.

4.1 Biological Effects of Laser Radiation

Laser radiation can damage living tissue by two basic mechanisms. For continuous wave lasers, the mechanism is a thermal process whereby a steady stream of photons is absorbed by the tissue until the natural cooling ability of the tissue is overwhelmed and its temperature rises to damaging levels. For pulsed lasers, the mechanism is one of acoustical blast or shock damage from individual pulses. In general, this second mechanism tends to be more important in inflicting serious permanent damage to tissue.

4.1.1 Eye Damage

By far the most important site of damage from laser radiation is the eye. The location and extent of the damage inflicted is dependent upon the wavelength of the radiation and the energy of the beam (or its individual pulses). Radiation with wavelengths in the ocular focus region (0.4 - 1.4 micrometers) is transmitted through the cornea and focused by the lens on the retina with a magnification of up to 100,000 times. Laser beams with wavelengths in this range have the greatest potential for seriously damaging the eye by virtue of their ability to form permanent lesions on the retina.

Figure 4. Absorption and Transmission of Laser Light by

by Components of the Ocular System

Laser radiation with wavelengths outside the ocular focus region are largely absorbed by the cornea and thus do not pose a hazard to the retina. In the infrared (1.4 -1000 micrometer wavelength), excessive exposure causes a loss of transparency or surface irregularities in the cornea. In the ultraviolet (0.2 to 0.4 micrometer wavelength), excessive exposure produces photophobia (intolerance to light) accompanied by redness, tearing, conjunctival discharge, surface exfoliation (removal of the surface in scales or laminae), and stromal haze (cloudiness in the connective tissue or main body of the cornea).

4.1.2 Skin Damage

The skin's large surface area makes it readily available to accidental and repeated exposures to laser radiation. In the visible and infrared regions, the biological significance of skin irradiation is considerably less than that for the eye since skin damage is usually repairable. Effects vary from mild erythema (reddening) to blisters or charring. Depigmentation, ulceration, and scarring of the skin as well as damage to underlying organs can occur from extremely high-powered laser radiation. Though little data exists on the effects of skin exposure to ultraviolet laser radiation, the ability of the ultraviolet portion of solar radiation to produce various grades of erythema, skin aging, and cancer is well known.

4.2 Other Laser Hazards

The potential health and safety hazards associated with laser systems are not limited to the effects of the beam upon the eye or skin from direct or specularly reflected beams. A number of other physical, chemical, or electrical hazards may be posed from the operation of these systems.

4.2.1 Airborne Contaminants

Many of the materials required for laser operation as well as materials produced by the laser during operation (as by beam interaction with target materials) are potentially hazardous to operating personnel. Laser media, fuels, or exhaust products can include carbon monoxide, carbon dioxide, nitrogen oxides, sulfur dioxide, sulfur hexafluoride, nitrogen, helium, hydrogen, fluorene, hydroflouric acid, and various refrigerants. Beam interaction with the target can produce a "plume" which, depending upon the nature and composition of the target, can include metallic fumes and dusts, chemical fumes, organic solvents, polycyclic aromatic compounds, hydrogen cyanide, or biological contaminants. All of these materials pose potential inhalation hazards to those working with or near the laser system.

4.2.2 Explosions

Laser targets, bulbs, and high-pressure filaments and lamps may shatter during operation propelling projectiles throughout the vicinity of the laser. For this reason, adequate enclosure of these components is essential.

4.2.3 Fire Hazards

Solvents used in dye lasers are extremely flammable and have led to numerous fires in laboratories throughout the United States. Many of these fires were started by a high-voltage pulse through an alcohol solvent. High-power continuous wave infrared lasers can also pose substantial fire hazards. The direct and specularly reflected beams of these lasers can ignite flammable materials in the area of laser operation.

4.2.4 Electrical Hazards

The high-energy electrical power supplies of many laser systems pose a serious hazard of electrical shock or electrocution. In fact, electrocution is the major cause of death from accidents involving lasers.

4.2.5 Cryogenic Hazards