Safety Manual

Table of Contents

I. INTRODUCTION

Welcome to the School of Engineering and Applied Sciences / Physics Department/ Earth & Planetary Sciences Department Safety Manual. All new personnel, staff and students, must read this information with diligence for the subject of safety must not be taken lightly. The content of this manual was written to serve as an overview of the potential hazards that exist in our environment and is not meant to be the definitive word on any of the covered subjects areas. Further, in-depth training, is a necessity if you work in a hazardous environment such as one encounters in experimental research.

To reiterate, the message that one must employ safe practices in the workplace must not be dismissed. Even the most intelligent people can (and do) have serious accidents if they are not properly trained or if they do not have the appropriate level of respect for the potential hazards at hand. With that said, please read on, and good luck with your work.

1. INTRODUCTION
   1. Administration of Safety Program
   2. Assignment of Responsibility
   3. Record of Accidents
   4. Working Alone
   5. Safety Questionnaire
2. GENERAL SAFETY PRACTICES IN THE LABORATORIES
   1. Electrical Safety
   2. Laboratory Gases
   3. Chemicals: Use, Storage and Disposal
   4. Ultraviolet Light
   5. Machine Shop
   6. Portable Hand Tools
   7. General "Housekeeping"
   8. Lasers
   9. Radiation Safety
   10. Repetitive Strain Injury
3. BUILDING SAFETY
   1. General Storage
   2. Emergency Procedures
   3. Fire Extinguishers
   4. Emergency Equipment--First Aid
   5. Poison Gas Leaks
   6. Personal Safety

I.A. Administration of Safety Program

Harvard University is committed to conducting research in the safest possible environment. Safety ultimately depends on the vigilance and concern of each research group, with the Principal Investigator bearing the primary responsibility for appropriate safety procedures and their implementation. To aid in this effort, DEAS established a standing committee on safety in October, 1983, consisting of representatives from all of the major research laboratories and members of the School's administrative and support staff. Since a significant overlap existed in research, several years ago the Physics Department joined this group. In 2004, EPS also became a member.

Each member of the safety committee is a Safety Officer with the responsibility of implementing safety procedures and encouraging safe practices in their areas.

Since some safety questions can be open to personal interpretation, situations that cannot be resolved locally are brought to the attention of the Executive Committee of the Safety Committee. The Executive Committee includes the Associate Dean of the School, the Chair of the Safety Committee, SEAS Facilities Manager, the Physics Lab Director, the EPS Lab Director, and one or two other individuals.

I.B. Assignment of Responsibility

Principal Investigators ultimately have the responsibility for safety in their laboratories; the Safety Committee, under authorization from the Dean of the School and the Chairs of the Physics & EPS Departments, acts in support of the Principal Investigators. Safety Officer work to develop safety procedures, educate research personnel, identify safety problems, and implement the safety program.

Safety is obviously everyone's responsibility and, in the end, all personnel must work in accordance with accepted safe practices and report any unsafe conditions.

I.C. Record of Accidents

Should you be involved in an accident, University and departmental policies require that you inform your Supervisor, Department Head, and the Chair of the Safety Committee, and Harvard's University Health Services. An Accident Report form, which are available from your local Safety Officer, SEAS Accounting Office, and on-line , must be filed for every accident, no matter how minor.

Reporting an accident has three important functions:

1. It alerts your Supervisor or Department Head to the accident. They, in turn, have the responsibility of reporting accidents to Human Resources for insurance coverage and to comply with State regulations in cases involving Workmen's Compensation;
2. Reporting accidents to the University Health Services minimizes the chance that an apparently minor injury might become aggravated; and
3. It alerts the School and the University to potentially unsafe practices.

I.D. Working Alone

Harvard's policy statement indicates that working alone with hazardous materials or equipment in isolated areas is recognized as fundamentally unsafe. It is the responsibility of each director of a laboratory, department head, or administrative unit of the University to identify the hazardous or isolated areas under his/her jurisdiction where working alone is not allowed. Where hazards are identified, every effort must be made to minimize or eliminate them.

In the research environment, there are times when each of us works alone. Under the pressure and genuine excitement of performing research, it is sometimes tempting to conduct hazardous work alone. However, when safety issues are concerned, there is a point where one must draw the line and have another person present. Usually such situations are obvious. But if you are in doubt, the people listed as members of the Safety Committee are resources to be called upon. As the old saying goes, "a dead hero is still dead." If you are injured due to the fact that you were working alone when you should have been working with a partner, no one is going to praise you for your efforts.

I.E. Safety Questionnaire

In an effort to provide proper services for people who may work under hazardous conditions, a safety questionnaire has been developed for all new incoming personnel. This questionnaire is to be filled out by all incoming staff and students, and submitted to your local Safety Officer (or submit it electronically) before beginning any lab work.

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II. GENERAL SAFETY PRACTICES IN THE LABORATORIES

II.A. Electrical Safety

Electricity is found in every room and laboratory in the University. We tend to take it for granted and forget that inherent dangers can be present in the form of shock and/or fire hazards.

In general, it is important to remember one thing: IT IS THE CURRENT THAT KILLS, not the voltage level of the power source involved. When you accidentally make part of your body a part of an electrical circuit by simultaneously making contact with both a voltage source and a ground, the current that flows in your body determines the seriousness of the shock.

Body contact resistance varies from several kilohms (dry) to less than one kilohm (wet); internal body resistance is about 500 ohms from hand-to-foot, and about 100 ohms ear-to-ear. Since current equals voltage divided by resistance, it can be seen that sweaty hands in contact with a source as low as 100 volts can produce a body current of at least 100 milliamperes; enough to kill you if it passes through your body.

Generally, the results shown below in Table 1 from various levels are to be expected.

There is only one rule in working safely with electrical equipment: NEVER TAKE A CHANCE. If you have any doubts or questions, ask for the advice of knowledgeable people.

1. Electrical equipment should be intrinsically safe when part of an experiment or when used routinely in an area where there are flammable gases or liquids. Care must be exercised to identify possible sources of ignition.
2. As a general rule, electrical equipment should be properly grounded. In most cases, this means tying in the main building ground.
3. Flammable gas- or liquid-filled equipment should be analyzed to see if there is any danger of static discharge acting as an ignition source. A way to avoid this problem is to ground the piece of equipment. Take care that a good electrical contact always exists between the equipment and the ground.
4. All unused or unnecessary electrical equipment should be removed from the lab area and stored in a proper storage location.
5. All electrical equipment should be checked on a regular basis.
6. Leads with 50 or more volts should be shrouded or taped for shock protection.
7. A sign which states, "DANGER--HIGH VOLTAGE," should be easily visible when high voltage equipment is in use.
8. Know the location of circuit breakers and emergency power shut offs.
9. Turn off all power and ground all high-voltage points before working on apparatus. Be sure that all capacitors are completely discharged. Make sure that power cannot be accidentally restored by another person.
10. Move slowly around all electrical equipment to make sure that you are always in good balance. Do not lean on or casually touch apparatus.
11. Never work on live equipment when tired.
12. Never touch electrical equipment when standing on a damp floor or a metal floor. Do not handle electrical equipment if you or the equipment are damp or wet.
13. You should not use "cheater plugs" to unground oscilloscopes and other test equipment. It is far better to fix the problem than to try and circumvent it in an unsafe manner.
14. Do not use water on an electrical fire.
15. Never take a voluntary shock. Use a meter, not your hand, to see if power is present.
16. Use dry insulating material (rope, wood, clothing) to remove a victim from a live electrical circuit, if power cannot be turned off. Move quickly, as delay may be fatal. Yell loudly, "HELP", and call for emergency medical personnel.
17. CPR, by a certified person only should be started immediately on a victim whose heart has stopped beating, and be continued until the victim has regained consciousness and begins to breathe normally, or until a doctor takes charge.
18. Unfused extension cords present real dangers in the office. The tendency is to use them without regard for their current rating. If a 5 amp extension cord is used with a space heater, for example, the cord will heat up to the point of melting the insulation and presenting an extreme fire hazard. NEVER use unfused extension cords without first assuring yourself that you are not violating its current rating.

The Safety Committee has a fairly good video on the subject of electrical safety in the laboratory. To borrow it contact the Chair of the Safety Committee (5-4215).

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II.B. Laboratory Gases

The amount of stored energy in a standard lab size nitrogen bottle is equal to the amount of potential energy found in several pounds of dynamite. Adding to the explosion hazard is the fact that many of the gases used in research are highly toxic, flammable, and/or corrosive. Compressed gas cylinders are ubiquitous in many research labs and must be treated with the respect they deserve.

Safety Guidelines:

1. All cylinders MUST be tied down. CLAMPS ARE AVAILABLE IN THE CHEMISTRY STOCKROOM.
2. Do not drop cylinders or permit them to strike each other violently. A puncture or fracture can turn a cylinder into a bomb.
3. Cylinders must be protected from extremes of weather, from dampness (to prevent rusting), and from the direct rays of the sun.
4. Valve protection caps must be left in place until cylinders have been secured into position and are ready for use.
5. Avoid dragging, rolling or sliding cylinders, even for short distances. Use a suitable hand cart for moving.
6. NEVER tamper with safety devices on cylinders or valves (gas regulators). The type of gas regulator on a gas cylinder is specific to that compressed gas (i.e., a nitrogen regulator is different from a nitric oxide regulator). DON'T SWITCH THEM AROUND BY USING ADAPTERS. This is very dangerous. If in doubt as to which regulator is appropriate, ASK FOR ADVICE.
7. Never use cylinders that cannot be identified positively.
8. Promptly remove the regulators from empty cylinders and replace the protective caps at once. Mark the cylinder empty.
9. No part of a cylinder should be subjected to a temperature higher than 125o F. A flame should never be permitted to come in contact with any part of a compressed gas cylinder.
10. Store cylinders in appropriately ventilated cabinets or in an open storage area.
11. Never bleed cylinders completely empty. Leave a slight pressure to keep contaminants out.
12. Do not put oil or grease on the high pressure side of an oxygen, chlorine, or other oxidizing agent cylinder. An explosion can result.
13. Observe the following special rules when working with acetylene cylinders:
    • Acetylene cylinders are partially filled with acetone; always store them upright.
    • Do not use an acetylene cylinder which has been stored or handled in a non-upright position until it has remained in an upright position for at least 30 minutes.
    • Ensure that the outlet line of an acetylene cylinder is protected with a flash arrester.
    • Never exceed the pressure limit indicated by the warning red line of an acetylene pressure gauge.
    • Use the correct kind of tubing to transport the gaseous acetylene. Tubing materials such as copper and some brass alloys form explosive acetylides.

The disregard of appropriate safety procedures in the use of compressed gas bottles is one of our most serious threats to life and limb. People have been killed in the past, here at Harvard, by exploding gas cylinders. If one sees that a bottle with a regulator attached is not tied down, either find the person responsible for the bottle and tell that person to tie it down, or tie it down yourself. If there are any further problems, see your local Safety Officer.

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II.C. Chemicals: Use, Storage and Disposal

The use of prudent practices when using chemicals is essential. There have been many accidents at Harvard involving chemicals that were traced to either unsafe technique or insufficient knowledge of the chemicals being used. Fortunately, most of these incidents have been minor but several have ended up sending people to the hospital. Below is a list of guidelines that should always be employed when using chemicals.

Safety Guidelines:

1. Know what chemicals you are using, and know what their hazards might be before ever ordering the product.
2. Have only those quantities on hand which are needed.
3. Use the proper personal protective clothing (i.e. lab coat, gloves, eye protection, etc.) Do not wear shorts or sandals when working with hazardous chemicals.
4. Keep flammable chemicals from open flame or light, and store in approved containers.
5. Do not eat while working with chemicals. All food MUST be kept out of the laboratory. There have been several cases where government regulatory agencies have shut down University laboratories as a consequence of violating this rule.
6. Provide proper storage for chemicals in a well-ventilated area or, if necessary, in the hood.
7. Date all chemicals when received and write you name on the bottle.
8. Do not dispose of chemicals down the drain, as they can cause pollution and plumbing problems. If you work with chemicals you are required by Federal law to take initial training in the disposal of hazardous materials. Once this is done you are required to take refresher training once per year.
9. Seal and label containers in which there are toxic materials.
10. Call Environmental Health and Safety at 6-3322 to arrange for a hazardous waste pick up.

Problems originating from the use of chemicals and compressed gas cylinders can be decreased by storing only what chemicals and compressed gases are actively being used, and by storing only minimal amounts. It is not a wise way to save money by storing, for example, some toxic chemical because there is still $10 worth of that chemical in the bottle. The hazard to life is not worth the savings.

If chemicals must be stored, there are procedures that should be followed. All flammable chemicals should be stored in an approved flammable storage cabinet. If you don't know what this is, or if there is not one in your area, talk with your Safety Officer. Acids and bases should be stored in separate areas. Partitioning the bottom of a fume hood is a good place to store acids and bases. Toxics should be stored in a separate cabinet that is clearly labeled. This cabinet can be continuously vented or purgeable. Since there are several different methods for proper toxic chemical storage, the best tack to take is to consult your Safety Officer if this issue arises in your area.

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II.D. Ultraviolet Light

Ultraviolet light is a radiant energy which occupies the region between visible light and x-ray in the electromagnetic spectrum. The hazards of the emitted radiation depend upon the wavelength. The UV section of the spectrum is divided into three parts:

• UV-A (315-400 nm): radiation equivalent to that received from the sun, and unless a person is especially sensitive, the most that can happen to his/her skin is that it will tan.
• UV-B (280-315 nm): is the middle range of UV radiation, and it is more harmful.
• UV-C (180-280 nm): overlaps x-rays, and must be dealt with under extreme precautions.

Ultraviolet burns of the eye (actinic keratinitis) are very painful, but not normally of lasting effect (UV-A and UV-B). Typically, an individual is exposed at work and doesn't even realize it. Sometime that same evening or night the eyes become painful, feeling as if grains of sand are under the eyelid. Often the victim doesn't make the connection between working with UV-emitting light source and the pain being experienced. Some studies connect UV exposure to skin cancer; severe burns are also possible.

Any blemish that appears on the skin after exposure to long-term UV radiation should be examined by a physician.

1. All workers using UV emitting sources must have eye protection (goggles or normal glasses). Most plastics and all glass are an efficient shield for UV.
2. If you are working with UV-C or high doses of UV-A or B, you should also protect your skin. Special creams are available for this.
3. If you are working with a UV emitting source, be certain that other people in your area are guarded from direct radiation. The use of plastic shields and prominently placed signs are helpful. It is important to tell people not to look directly at the source. Also, be careful to avoid reflections from metal surfaces.

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II.E. MACHINE SHOP

Working with machine tools can be hazardous even for experienced machinists. We are fortunate in having these machines available for use; however, they must be used with great care. First, NO ONE IS PERMITTED TO USE THE MACHINE TOOLS WITHOUT THE EXPLICIT PRIOR APPROVAL of either the Director of the Scientific Instrumentation Shop (Gordon McKay Laboratory) or Stan Cotreau (Physics Department). Second, no one, with the exception, perhaps, of our professional machinist staff, is allowed to work alone with the machine tools. Free instruction regarding the safe use of machine tools is available through the Physics Department. If you want to use the machinery, you are urged to take this course. You must be certified as having been trained on any particular machine before you will be allowed use of that machine. In any case, the following safety guidelines should be followed at all times.

1. Use only the machines and equipment that you are qualified to use.
2. Check guards and safety devices. Make sure that they are in place and adjusted properly.
3. Never leave a machine running unattended.
4. To make any necessary adjustments, first turn the power off and wait until the machine has come to a standstill. Then make your adjustments.
5. Do not try to brake or slow down moving machinery with your hand or any other makeshift device.
6. Keep the machine clean (band saw, milling machine, etc.). If necessary, remove chips with a brush or tongs, but not with your hands--especially if the machine is in operation.
7. Make sure that you have properly protective clothing or equipment (eye shields, hearing protection, apron, shoes, etc.).
8. Do not wear loose clothing, long sleeves, ties, gloves, or jewelry while operating machinery.
9. Do not operate machinery in the shop without the knowledge of another person present in the laboratory. Wait until the next working day to do the work if you are by yourself.
10. If in doubt, ask one of the machinists for help, suggestions, or instruction.

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II.F. Portable Hand Tools

1. Use the proper tool for the job.
2. Keep tools in working condition (i.e., sharpened, grounded, properly wired, good handles, etc.).
3. Use tools in the manner for which they were designed.
4. Keep tools in a safe place--tool room or shop tool box.

The Safety Committee has a good video regarding how to use hand and small power tools in a safe manner. To borrow it contact the Chair of the Safety Committee (5-4215).

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II.G. General "Housekeeping"

In the laboratory and elsewhere, keeping things clean and neat generally leads to a safer environment.

1. Keep aisles and floors free of any unnecessary boxes, chemicals, cylinders, etc. Avoid slipping hazards by keeping the floor clear of ice, stoppers, glass rods, other small items, and spilled liquids.
2. Use the required procedure for the proper disposal of chemical wastes and solvents. (See Section II.C.).
3. Have only those materials in the work area that are necessary for the job.
4. Return any equipment, tools, or chemicals to their proper storage area.

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II.H. Lasers

Lasers are being used more and more as a tool of research. Because of the intense, coherent nature of the radiation emitted by lasers, there is a real potential for causing irreparable damage to skin and eyes. Before using any given laser, you MUST first figure out what class laser it is, and then make certain that ALL the appropriate safety precautions are taken. The following discussion (the bulk of which was taken from Laser Safety Training Manual by Rockwell Associates, Inc.) will not answer all of the questions relevant to the safe use of lasers. Even though this information is helpful and factual, it is the responsibility of all personnel to research the hazards involved with their particular system.

CLASS 1: Lasers and Laser Systems

Any laser or laser system containing such a laser that cannot emit accessible laser radiation levels in excess of the AELs (Class 1) for the maximum possible duration inherent in the design or intended use of the laser or laser systems. Such Class 1 lasers systems cannot, under normal operating conditions, produce an eye or skin hazard.

CLASS 2: Low Power Visible Lasers and Laser Systems

1. Visible (400-700 nm) continuous wave lasers or laser systems which can emit accessible radiant power exceeding the Class 1 AEL for the maximum possible duration inherent in the design of the laser or laser system (0.4 microWatts for an emission duration greater than 3 x 104 seconds) but not exceeding 1 mW. Because of the normal human aversion response to bright radiant sources, Class 2 lasers do not normally present a hazard, but may present some potential for hazard if viewed directly for extended periods of time (greater than 0.25 sec)--like many other conventional light sources.
2. Visible (400-700 nm) repetitively pulsed lasers (and scanning lasers) and laser systems which can emit accessible radiant power exceeding the appropriate Class 1 AEL for the maximum possible duration inherent in the design or intended use of the laser or laser system, but not exceeding the Class 1 AEL for a 0.25 second exposure. Note that the 0.25 second limit is considered to be the human aversion response time factor.
3. Visible (400-700 nm) repetitively-pulsed or continuous wave lasers or laser systems may be designated as Class 2A if the laser or laser system is to be used in a manner where the output beam is not intended to be viewed in normal use. The AEL for Class 2A is based upon maximum exposure time of one-thousand (103 ) seconds.

CLASS 3: Medium Power Lasers and Laser Systems

1. Far-infrared (1400-106 ) and ultraviolet (200-400 nm) lasers and laser systems which can emit accessible radiant power in excess of the Class 2 use of the laser system, but cannot emit: (a) an average radiant power in excess of 0.5 W for a classification duration greater than 0.25 second; or (b) a radiant exposure of 10 J/cm2 within an exposure time equal or greater than 0.25 second.
2. Visible (400-700 nm) continuous wave or repetitively-pulsed lasers or laser systems producing accessible radiant power in excess of the Class 1 AEL for a 0.25 second exposure (1 mW for a continuous wave exposure), but which cannot emit an average radiant power greater than 0.5 W. Continuous wave visible (400-700 nm) lasers having an output of 1-5 mW are designated Class 3A lasers and would not normally produce a hazard if viewed with the unaided eye for momentary periods (0.25 seconds). They may present a hazard if viewed with collecting optics.
3. Visible and near-infrared (400-1400 nm) single pulse lasers and laser systems which can emit accessible radiant energy in excess of the Class 1 AEL, but which cannot emit a radiant exposure that exceeds 10 J/cm2 (approximate fire-hazard point) or that required to produce a hazardous diffuse reflection (see Table 2). In general, Class 3 lasers (except the Class 3A subdivision) can produce a hazard if viewed directly. Except for the most powerful Class 3 lasers, focused on a diffuser under short range viewing conditions, this class will not produce a hazardous diffuse reflection.
4. Near-infrared (700-1400 nm) continuous wave lasers or repetitively-pulsed lasers which can emit accessible radiant power in excess of the Class 1 AEL for the maximum duration inherent in the design or intended use of the laser or laser system, but cannot emit an average power of 0.5 W or greater for periods in excess of 0.25 second.
5. Lasers and laser systems having an accessible output power between one and five times the lowest appropriate Class 3 AEL and which do not exceed the appropriate maximum permissible exposure as measured over the limiting aperture are designated as Class 3A. NOTE: For visible (400-700 nm) lasers and laser systems, the lowest Class 3 AEL is 1.0 mW, hence the Class 3A output may range from 1.0-5.0 mW. The MPE applicable is that for 0.25 second; thus, from Table 3, the MPE = 1.8 CA (0.25) 3/4 mJ/cm2 , where CA = 1.0 for visible frequencies and may be determined from Figure 1 for near-infrared frequencies. Thus, MPE = 1.8 x 0.353 = 0.64 mJ/cm2. Thus a Class 3A visible frequency laser has an output of 1.0-5.0 mW contained in an irradiance of 2.5 mW/cm2.

CLASS 4: High-Power Lasers and Laser Systems

1. Ultraviolet (200-400 nm) and infrared (1400-106 nm) lasers and laser systems which emit: (a) an average accessible radiant power in excess of 0.5 W for periods greater than 0.25 second; or (b) a radiant exposure of 10 J/cm2 with an exposure duration of 0.25 second or less.
2. Visible (400-700 nm) and near infrared (700-1400 nm) lasers and laser systems which emit: (a) an average accessible radiant power of 0.5 W or greater for periods greater than 0.25 second; or (b) a radiant exposure in excess of 10 J/cm2 , or that required to produce a hazardous diffuse reflection for periods less than 0.25 second (see Table 2).

Maximum permissible exposure (MPE) limits for direct ocular exposures are given in Table 3; for viewing a diffuse reflection in Table 2; and for skin exposures in Table 4. Wavelength correction factors (700-1400 nm) are given in Figure 1. Repetitively pulsed (scanning) laser MPE corrections are given in Figure 2. The MPE levels provided in these tables and figures are from the Z-136.1 Safe Use of Lasers Standard of the American National Standards Institute.

1. Always wear goggles that offer protection against the specific wavelength of the laser in use. If more than one wavelength is being used, additional goggles specific for each wavelength are required. No available spectacles protect against all laser wavelengths.
2. Never look directly at the beam or pump source.
3. Never view the beam pattern directly; use an image converter or other safe, indirect means. To decrease reflecting hazard, do not aim by looking along the beam.
4. Do not allow any objects that cause specular reflections to be present in or along the beam. Even spherical buttons and polished screw heads can be dangerous.
5. Keep a high general illumination level in areas where lasers are in operation. Low light levels cause dilation of the pupils, and thereby increase the hazard.
6. Display warning signs in the laser areas.

Laser radiation of sufficient intensity and exposure time can cause irreversible damage to the skin and eyes of a person. The principal cause of tissue damage is thermal in nature. The thermal damage process is generally associated with lasers operating at exposure times greater than 10-5 seconds and in the wavelength range extending from the near ultraviolet to the extreme of the far infrared spectral region (315- 106 nm). Healing of laser induced skin lesions is similar to any localized thermal wound and should be medically treated in a similar fashion. Laser induced lesions on the retinal tissues of the eye will usually cause irreversible vision function loss and cannot be medically treated.

The principal hazard associated with laser radiation is exposure to the eye. This is particularly important in the visible and near-infrared spectral regions (400-1400 nm). There are, however, other serious potential hazards in the other spectral regions. Excessive ultraviolet exposure produces an intolerance to radiant exposure (photophobia) accompanied by redness, tearing, discharge from the mucous membrane that lines the inner surface of the eyelid (conjunctiva). corneal-surface cell-layer splitting (exfoliation) and stromal haze. This is the syndrome of photokeratitis which is a radiant energy-induced damage to the outer epidermal cell layer of the cornea often called "snow blindness" or "welder's flash."

The ocular hazards represent a potential for injury to several different structures of the eye (see Figure 3), generally depending upon which structure absorbs the most radiant energy per unit volume of tissue. Retinal effects are possible when the laser emission wavelength occurs in the visible and near-infrared spectral regions (400-1400 nm). Laser radiation directly from the laser or from a specular reflection entering the eye at these wavelengths can be focused to an extremely small spot-image on the retina causing an excessive irradiance (W/cm2) or radiant exposure (J/cm2) incident on the retinal tissues even for modest corneal exposure levels.

In the visible portion of the spectrum (beginning near 380 nm and extending to nearly 750 nm) the cornea, lens, and associated eye media are largely transparent, as they neither absorb nor scatter light to any significant degree. Only about 5% of the incident radiation is used for vision; the remainder is absorbed in the pigment granules in the pigment epithelium layer of the retina and the choroid layer which lies under the rods and cones (photo-receptors). The absorbed energy is converted into heat and, if the incident radiant laser energy is too great, can cause an irreversible retinal burn.

A retinal injury occurring in the macula is a very serious trauma since the vision functions are most highly developed in that area. Of major concern is the fact that blindness can be the result of a laser exposure that lasts only an infinitesimal fraction of a second! A macular burn would be the most probable result if the individual is viewing the beam directly or via a specular reflection under conditions where the eye is resolving the point source directly onto the macula.

A transition zone between retinal effects and effects on the front segments of the eye (cornea, lens, aqueous media) begins at the far-end of the visible spectrum and extends into the infrared 'A' region (780-1400 nm). In the infrared 'B' region (1400-3000 nm) damage is observed to both the lens and cornea. The ocular media becomes opaque to radiation in the infrared 'C' region (3000-106 nm) as the absorption by water is very high in this spectrum region. In the infrared 'C' region (3000-106 nm), as in the ultraviolet 'A' and 'B' regions (280-400 nm), the threshold for damage to the cornea is comparable to that of the skin. Damage to the cornea, however, is much more disabling and of much greater concern.

There are also several good Web sites with additional information. These sites include: Lawrence Livermore National Laboratory , The Laser Institute of America , and Rockwell Laser Industries .

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II.I. Radiation Safety

Radiation consists of energetic particles and waves, the most dangerous of which are energetic enough to ionize molecules and cause direct chemical damage to the body. Lower-energy radiation may also cause injury if it is intense enough. Special safety precautions must be taken when using sources of radiation because radiation cannot be sensed. Hence, safe use of radioactive sources, accelerators, and other radiation-producing devices requires familiarity with radiation's properties and effects.

Ionizing radiation can either interact directly with matter, or cause ionization indirectly. Directly-ionizing radiation consists chiefly of highly energetic charged particles such as electrons, protons, (-, and (-particles. As these particles pass through matter they interact electromagnetically with electrons and eject them from their atomic orbits. One important source of charged-particle radiation is the radioactive decay of nuclei. Other sources are the electrons and protons excited through the effects of indirectly-ionizing radiation on matter. Generally it is easy to shield directly-ionizing particles, because they interact frequently with molecules along their path, expending all their energy within a short distance. A typical (-particle, for instance, will not even penetrate the outer dead layer of skin. Directly-ionizing particles are most dangerous when their sources enter the body either through inhalation or ingestion, because then the radiation affects living tissue rather than dead skin, and also because all the energy is deposited inside the body in a highly localized region.

Indirectly-ionizing radiation (i.e. neutrons, x-rays, and (-rays) can be much more penetrating, X-rays and (-rays can travel quite deeply into a material before either scattering off an electron or being absorbed. Damage is then done to the body by the electrons excited by the radiation. X-rays typically require a few millimeters of lead to be stopped; higher-energy photons are more penetrating and therefore require shielding. Neutrons cause damaging ionization in several ways. They can (1) collide with protons, transferring energy to them; (2) decay into protons and electrons; or (3) induce nuclei to decay. Neutrons interact weakly with matter since they only interact with other nuclear constituents at ranges of order 10-13 centimeters. Neutrons are best shielded with proton-rich materials such as water or graphite.

Some examples of non-ionizing radiation are microwaves and radio-frequency waves. The most obvious way in which these radiations can harm is by heating tissue. Sensitive tissue such as the cornea of the eyes is especially vulnerable. There is also some evidence that radiation which is not intense enough to deposit significant heat may also do damage, but interpretation of evidence remains controversial.

Radiation is measured in various units depending on whether one is interested in the number of decays, the ionization produced, the energy deposited, or the biological damage. Table 5 below gives a list of common units and their definitions.

The most relevant measure for human safety is the Roentgen equivalent in man (rem), which characterizes the biological damage likely to be done. A rem is defined as the product of the quality factor (QF) of the radiation, and the number of rads of radiation. One Roentgen of x-ray radiation produces approximately one rad of absorbed dose, and for rough calculations can be considered equivalent. The QF describes the harmfulness of a given amount of energy of a particular radiation and is normalized to one for electrons, positrons, and x-rays. The rem exposure thus gives an indication of the damage done. Table 6 gives practical values of quality factors for various types of radiation.

Ionizing radiation directly affects cell chemistry. It may destroy a cell's ability to function or cause genetic damage to it, which can lead to cancer. Damage to reproductive cells, both in males and females, can cause birth defects; pregnant women should be especially cautious. Table 7 lists the biological effects of various external radiation doses.

It is important to consider separately the effects of radioactive materials which enter the body. These materials deposit radiation continuously into a small, localized area, and over time deposit a substantial dosage. For this reason federal law prohibits food and utensils in the same room with radioactive materials.

The effects of non-ionizing radiation are less well understood. Microwaves can cause damage by directly heating tissue. Some potential exposure effects are: inflammation of organs, fetal anomalies, metabolic changes, lens opacity (80 mW/cm2, 1 hour daily, 20 days), cataract, headache, fatigue, excitability, and possible mutagenic effects. Microwave field intensities above around 1 mW/cm2 should be considered dangerous.

Three principles useful in radiation protection are time, distance, and shielding. One must try to minimize the time of exposure to radiation, keep as much distance as possible from sources of radiation, and make every effort to shield radiation. Maintaining distance from a radioactive source has a two-fold advantage. First, the intensity of radiation from a point source decreases as the inverse square of the distance, so twice the distance can give one-quarter the exposure; second, the intervening air absorbs radiation. For weakly-penetrating sources such as ( emitters, simple precautions such as using a pair of tweezers to hold the substance can yield a significant reduction in exposure. For highly-collimated sources such as used in x-ray spectrometers this rule is less important.

Shielding is also an essential factor. Directly-ionizing radiation, which interacts strongly with matter, is rather easily shielded. In fact, this property can sometimes be a problem: (-particles from 3H and 14C, two very common radioactive isotopes used in laboratories, cannot be detected with a Geiger-Muller counter because they cannot penetrate the window of the detector.

The maximum thickness of shielding material that charged particles of a certain energy and type can penetrate is called the range. Ranges in unit density materials for emissions from several common (-emitting isotopes are included in Table 8. Increasing the density of the shielding material decreases the particle range proportionately. However, low-atomic number materials such as Lucite or aluminum are preferable to lead or steel for shielding energetic (-emissions, because the particles are more likely to produce penetrating x-rays through interaction with targets having a high atomic number. In fact, such x-rays are a primary hazard of instruments such as electron microscopes, in which electrons accelerated through high voltages strike metal parts of the instrument.

Indirectly-ionizing radiation (uncharged particles), which interacts only weakly with matter, presents different problems in shielding. Since this kind of radiation is typically attenuated in an exponential fashion, x-ray or (-ray shielding is often characterized by the concept of a "half-value layer," or HVL (mathematically similar to the "half-life" used to characterize the exponential decay of a radionuclide). The HVL is defined as the thickness of shielding needed to reduce the intensity of radiation by one-half. The magnitude of the HVL is a function of the type and energy of the radiation and the density of the shielding material.

One should keep in mind an important difference between shielding directly-ionizing and indirectly-ionizing radiations. Essentially all the (- or (-particles from a source, independent of the intensity of the source, are stopped by the shielding material within the maximum range. In contrast, increasing the intensity of an x-ray, (-ray, or neutron source requires that the shielding be increased. For example, a lead shield that prevents penetration of 99.9% of (-rays from a 60Co source might be suitable if 1,000 photons/second were incident on the shield, but insufficient if the source intensity were increased to 106 photons/second.

1. No smoking or eating permitted in the work area.
2. Never pipette by mouth.
3. Gloves and laboratory coat are required when using radionuclides.
4. Prescribed personnel monitors must be worn.
5. Hands, shoes, and clothing should be monitored frequently.
6. Work with radioactive materials in an approved hood or glove box, unless the safety of working on an open bench can be demonstrated.
7. Radionuclide work should be conducted in an impervious tray or pan, lined with absorbent paper.
8. Utilize shielding and distance whenever possible.
9. Dispose of liquid and solid radioactive waste in the approved containers provided.
10. Refrigerators containing radionuclides shall not be used for storing food.
11. Monitor radionuclide work areas at least once daily for contamination and make notation of this survey in laboratory records.
12. Thoroughly wash hands after manipulating radionuclides, before eating or smoking, and on completion of work.
13. Maintain records of receipt, use, transfer, and disposal of radioactive materials.
14. Report accidental inhalation, ingestion, injury, or spills to your supervisor and to Environmental Health and Safety's Radiation Protection Office (5-2060).
15. In the event of a significant spill or accidental release of radioactivity, one should restrict access to the contaminated area, remove any contamination on personnel, and prevent the spread of contamination. Notify Environmental Health and Safety immediately (5-2061).
16. Review pertinent safety practices frequently, especially before using a new radionuclide.
17. Assure compliance with University radiation safety guidelines and Title 10, Code of Federal Regulations, Parts 19 and 20.

X-ray generators: There are a number of x-ray sources present in the School of Engineering and Applied Sciences, both fixed-tube and rotating-anode. These can pose a serious radiation risk if not handled properly. Appended to this chapter is a brief article by the International Union of Crystallography's Commission on the Crystallographic Apparatus which discusses radiation hazards associated with X-ray spectrometers.

Rutherford Backscattering: The Rutherford backscattering facility in Gordon MacKay Laboratory is also a potential radiation hazard; here the main threat is from neutrons liberated in nuclear reactions initiated by the energetic (-particles. Tables 9, 10, and Figure 4, characterize some of the possible reactions which can occur.

This chapter is intended to familiarize the reader with the various safety hazards posed by laboratory radiation. Much of the information presented here is drawn from Jacob Shapiro, Radiation Protection: a Guide for Scientists and Physicians, 2nd ed. (Cambridge MA: HUP, 1981), and from the lecture on radiation safety given by Michael Aziz (Harvard University, SEAS Safety Seminar Series, May 1988). A manual published by the Harvard Environmental Health and Safety Office, Regulations for the Use of Radioisotopes at Harvard University, provides more detailed information as well as specific regulations for wearing personal monitoring devices and posting radiation warning signs. Any further questions should be directed to the Harvard Environmental Health and Safety Office at 495-2060.

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II.J. Repetitive Strain Injury

With the use of computers becoming all pervasive, the number of reported cases of Repetitive Strain Injury (RSI) are rapidly increasing. RSI is a catch-all phrase for several different types of injuries caused by repetitive motions such as those encountered at the keyboard. These injuries include neck and back injuries, eye strain, and carpal tunnel syndrome. Pro-active RSI prevention is the best insurance policy to avoid injury. RSI prevention includes the proper set-up of workstations, taking breaks from the repetitive activity, and specific exercises. For further information see the RSI Action Home Page as well as the MIT RSI Home Page.

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III. BUILDING SAFETY

III.A. General Storage

1. Put tools back in their storage area if not in use.
2. Return any chemicals which are not being used to their proper storage area (see section II.C.).
3. Do not store empty and full cylinders of gases or liquids together (see sections II.B. and II.C.).
4. Paper, cloth, or other solids, if soaked with a flammable or combustible material, should be placed in a recognized disposal container.
5. Store chemicals and combustible materials away from flame. Flammable chemicals should be stored in an approved flammable storage cabinet. (See section II.C.).
6. Never block routes of egress.

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III.B. Emergency Procedures

Below is a list of phone numbers that might come in handy in an emergency:

HARVARD POLICE:	495-1212
CAMBRIDGE POLICE:	864-1212
FIRE/RESCUE SQUAD:	495-1511
SAFETY OFFICER:	See List
ED JACKSON:	495-2840
ED KOZLOWSKI:	495-2908
LENNY SOLOMON:	495-4215
DAVID NORCROSS:	495-2620
STUART MCNEIL:	495-2874
PAUL KELLEY:	495-3949
JERRY CONNORS/MIKE PATERNO:	495-3076

IN CASE OF FIRE:

Go to the nearest telephone and dial the fire/rescue number (5-1511) or the Harvard police (5-1212). If a fire is out of control call the Cambridge Fire Department immediately by pulling the nearest fire alarm box located in the corridor or stairwell. If there is time to talk to someone over the phone, give your location (building and floor) and your name. Emergency numbers are located on all telephone cradles.

Give the alarm first, after which an attempt can be made to put out the fire. It is better to have the fire department respond and find the fire out than to delay the arrival of help. Alert the Safety Officer on your floor.

If a fire alarm sounds in your area, you MUST leave the building. Please refer to our building evacuation procedures.

DO NOT DELAY evacuation by locking files, doors, or desks. Be familiar with an alternate route if the first exit is blocked. If confronted with smoke or fumes, keep your head as close to the floor as possible. Use a wet handkerchief, if possible, as a filter over mouth and nose. Above all, keep calm.

The electrical power to the elevators may be cut off and you may be caught between floors. After leaving the building, proceed to a distance of 50 feet and assemble with your group. Do not reenter the building for any reason until an "all clear" is given by the fire department.

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III.C. Fire Extinguishers

Fire extinguishers provided are--at best--first aid instruments to be used in the initial stages of a fire. All personnel are requested to know the location and types of extinguishers in the area and be familiar with their method of operation. Reviewing the fire extinguisher classification system will aid you in selecting the right extinguisher during an emergency situation.

TYPES OF FIRES:

• Class A Fire: Wood, paper, textiles, other ordinary combustibles.
• Class B Fire: Flammable liquids, oils, solvents, paint, grease, etc.
• Class C Fire: Electrical--live or energized electric wires or equipment.
• Class D Fire: Metals (sodium, calcium, potassium, magnesium, etc.)

TYPES OF EXTINGUISHERS:

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III.D. Emergency Equipment--First Aid

Regarding first aid kits, the following statements clarify the policy of the University Health Services:

The reasons for this policy are:

• Maintenance of first aid kits is likely to be lax;
• they give a false sense of security;
• minor cuts or injuries treated without medical supervision are more likely to result in a serious injury or condition; and
• there are no records of injuries; such records are necessary to protect both the individuals involved and the University.

There is, however, a practical need for emergency kits that can be used to save a life until medical care can be instituted. The purposes of the contents of the emergency kits are to: 1) control bleeding; 2) treat shock; 3) neutralize chemicals; and 4) control personal injury resulting from burning clothing. It is therefore recommended that first aid kits as such be abandoned and be replaced by emergency kits containing the following items:

• General: compress bandages, triangular bandages, blankets, and a stretcher (optional).
• Specific: Certain specific items such as neutralizing solutions should be included in specific areas. These should not necessarily substitute for a thorough flushing of the contaminated area of the body with water either by local shower or by spray attachment at sinks.

The presence and use of emergency kits should be known to all personnel. The inclusion of "specific" items, such as sodium bicarbonate solutions for acid spills, is left to the discretion of individual laboratories.

Familiarize yourself with the location of emergency showers and eye washes. The emergency showers and eye washes can be located on the floor plans included in Appendix B. This equipment should be checked regularly to flush the lines of any rusty water.

REPORT ALL INJURIES to the University Health Services and to the appropriate department.

First Aid training and certification by the Red Cross is offered during the Spring Safety Seminar Series.

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III.E. Poison Gas Leaks

1. Store poisonous gases in a well-ventilated area.
2. Self-contained breathing apparatus should be available and in a convenient location for emergencies. Personnel must be trained to use this equipment. (See Appendix B, Building Floor Plans)
3. The exits in any area where poisonous gases are used should be sufficient so that, in the event of an emergency, all personnel in that area can get out.
4. All sources of ignition must be shut off.
5. The Engineering Sciences Lab has a "closed-loop" ventilation system such that virtually no fresh air enters the system. Any gas that leaks will be rapidly distributed throughout the building. If you work in this building, contact Ed Jackson (5-2840) for the location of the emergency shut-off valve.
6. Notify the appropriate authorities of the situation:

   Mike Labosky	6-0724	(Safety Engineer)
   Garrett Burke	5-3055	(Industrial Hygienist)
   Local Safety Officer	5-	(See List)
   Ed Jackson (SEAS)	5-2840	(Building Maintenance)
   Stuart McNeil (Physics)	5-2874	(Building Maintenance)
   Jerry Connors/Mike Paterno (EPS)	5-3076	(Building Maintenance)
   Lenny Solomon	5-4215	(Chairman, SEAS/EPS/Physics Safety Committee)

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III.F. Personal Safety

The issue of personal safety pertains to hazards in the laboratory and to the possibility of theft, vandalism, and assault by strangers with access to School buildings. Section I.D. discusses the danger of working alone with regard to laboratory hazards.

1. Note the presence of strangers in the building. If appropriate, ask their business, escort them to an exit, or call the police.
2. Do not prop open locked doors.
3. If you come into the building during off hours, let someone know where you are and how long you expect to be there. Keep the doors to the outside locked as well as the doors to your work area, if appropriate.
4. If you feel yourself to be in danger, call the Harvard Police (5-1212). As a last resort, pull the fire alarm.