Download LASER AND ELECTRICAL SAFETY AND LASER CLASSIFICATION

LASER AND ELECTRICAL SAFETY AND
LASER CLASSIFICATION
ACLaSS
PI/PD: Felix J. Seo
Eye Hazard
Although the lasers you are using have very low power, the focusing properties of the eye and
the sensitivity of the eye’s retina will still make them potentially harmful. A damaged retina
cannot be repaired. As with all laser sources, please obey the following safety guidelines:
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Never stare in the laser beam.
Never look down, or close to the unexpanded beam.
Remove all unnecessary refractive items from work area, especially unused optical components.
Remove (or cover) all bracelets, rings, necklaces, and watches when working with laser beams.
Keep all beams confined to the optical breadboard. (Make sure no beams leave the table.)
Block all stray beams that leave the immediate work area.
Avoid optical system layouts that produce vertical beams.
Keep all beams at a fixed height above the optical table and parallel to the table, wherever
possible. (No beams allowed flying up into the air where they can strike someone bending over
the table.)
Never sit down or bend so that your eyes are at beam level. In case you drop something, and
need to bend to pick it up, cover your eyes as you pass through the level of the beams.
Keep your head above the plane of the work area.
Do not use an eyepiece, including camera eyepiece, to view last light.
Walk an index card along the beam path, determine all extraneous reflections and block them.
(All beams should end in a beam block.)
With high energy beams, be careful when you bend over the table that loose clothing does not
fall through a beam and is burned or that pieces of jewelry (necklaces, etc.) do not pass through
the beam causing an unpredictable reflection.
Wear safety goggles whenever practical. Always wear goggles when invisible beams are in use
(infrared, or UV).
Be sure that other persons in the room are aware of any laser hazards. Close outside doors.
These are rules which should be followed in all laser labs (if exceptions are necessary, other
safeguards should be put into place). No experiment is so important that there is no time to
follow them. Note that the rules overlap so that if one is overlooked, another will still serve to
help protect against injury.
It is especially important to follow these guidelines with laser beams in the infrared and
ultraviolet, which are invisible and therefore hard to locate. Unexpected reflections from optics
with these lasers are especially hazardous, so the use of redundant safety rules is very important.
While most common injury due to lasers is eye damage, other possible sources of harm are:
1. Setting clothes on fire
2. Burning skin or hair
3. Electrical shock due to high voltage power supplies
This is especially hazardous in high power lasers which are water cooled. In this case, it is
possible that you will have the very lethal combination of spilled water and high voltage. Turn
off the electrical power whenever power whenever water is spilled!
ACLaSS
PI/PD: Felix J. Seo
Optical Safety
Because of its special properties, laser light poses safety hazards not associated with light from
conventional sources. The safe use of lasers requires that all laser users and everyone else near
the laser system are aware of the dangers involved. The safe use of the laser depends upon the
user becoming familiar with the instrument and the properties of intense and coherent beams of
light.
The greatest concern when using a laser is eye safety. In addition to the main beam, there are
often many smaller beams present at various angles near the laser system. These beams are
formed by specular reflections of the main beam at polished surfaces such as lenses or beam
splitters. While weaker than the main beam, such beams may still be sufficiently intense to cause
eye damage.
Laser beams can be powerful enough to burn skin, clothing or paint. They can ignite volatile
substances such as alcohol, gasoline, ether and other solvents, and can damage light-sensitive
elements in video cameras, photomultipliers and photodiodes. The laser beam can ignite
substances in its path, even at some distance. The beam may also cause damage if contacted
indirectly from reflective surfaces. For these reasons the user is advised to follow the precautions
below.
1. Observe all safety precautions in the Preinstallation and Operator's manuals.
2. Extreme caution should be exercised when using solvents in the area of the laser.
3. Limit access to the laser to qualified users who are familiar with laser safety practices and
who are aware of the dangers involved.
4. Never look directly into the laser light source or at scattered laser light from any reflective
surface. Never sight down the beam into the source.
5. Maintain experimental setups at low heights to prevent inadvertent beam-eye encounter at
eye level.
6. As a precaution against accidental exposure to the output beam or its reflection, those using
the system should wear the appropriate laser safety glasses as designated by the wavelength
being generated.
7. Avoid direct exposure to the laser light. The intensity of the beam can easily cause fleshes
burns or ignite clothing.
8. Use the laser in an enclosed room. Laser light will remain collimated over long distances and
therefore presents a potential hazard if not confined.
9. Post warning signs in the area of the laser beam to alert all laser users and everyone else near
the laser system of the hazards specific to the class of laser present.
10. Advise everyone using the laser of these precautions. It is good practice to operate the laser
in a room with controlled and restricted access.
ACLaSS
PI/PD: Felix J. Seo
Electrical Safety
Most, if not all, Class III and Class IV laser systems (see the next section for information relating
to classification of laser systems) utilize high-level AC and DC voltages in both the laser head
and power supply. All Coherent laser systems are designed for operation with the laser head and
power supply covers closed. Only trained personnel aware of the hazards involved should
remove the protective covers.
Classification Criteria
The government recommended safety practices for a given laser system will depend on its
classification. The following list highlights the criteria used to classify lasers, as well as listing
the key safety considerations when operating a system within the indicated classification. See
"Code of Federal Regulations" for a comprehensive discussion of these safety topics.
Wavelength:
If the laser is designed to emit multiple wavelengths the classification is based on the most
hazardous wavelength.
Output Characteristics:
For continuous-wave (CW) or repetitively pulsed lasers the average output power (watts) and
limiting exposure time inherent in the design are considered. For pulsed lasers the total energy
per pulse (joule), pulse duration, pulse repetition frequency and emergent beam radiant exposure
are considered.
Laser Classification
Class I Lasers
These systems are also classified as "Exempt" lasers. They are normally not hazardous with
respect to continuous viewing, or are designed in a way that prevents human access to laser
radiation (e.g., laser printers).
Class II Lasers (Low Risk)
These lasers emit visible light, which, due to normal human reflex responses, do not present a
hazard. However, a safety risk would be posed if the output source were brought to within close
proximity of the eye and then viewed for an extended period of time.
Class III Lasers (Moderate Risk)
Class III lasers can cause eye injury if viewed momentarily, but are not capable of causing
serious skin injury or hazardous diffuse reflections without the use of collecting/conditioning
optics (e.g., fiber optics, telescopes, etc.).
Class IV Lasers (High Risk)
ACLaSS
PI/PD: Felix J. Seo
These lasers present an eye hazard from direct and diffuse reflections. In addition, class IV lasers
can cause combustion of flammable materials and produce serious skin burns and injury from
direct exposure. Most laser systems manufactured by Coherent fall into this classification.
ACLaSS
PI/PD: Felix J. Seo
LABORATORY REGULATIONS AND
CHEMICAL SAFETY PRECAUTIONS
ACLaSS
PI/PD: Felix J. Seo
LABORATORY REGULATIONS AND CHEMICAL SAFETY PRECAUTIONS
General Guidelines
1. Conduct yourself in a responsible manner at all times in the laboratory.
2. Be familiar with your lab assignment before you come to lab. Follow all written and verbal
instructions carefully. If you do not understand a direction or part of a procedure, ask the instructor before
proceeding.
3. Never work alone. No student may work in the laboratory without an instructor present.
4. When first entering a science room, do not touch any equipment, chemicals, or other materials in the
laboratory area until you are instructed to do so.
5. Do not eat food, drink beverages, or chew gum in the laboratory. Do not use laboratory glassware as
containers for food or beverages.
6. Perform only those experiments authorized by the instructor. Never do anything in the laboratory that is
not called for in the laboratory procedures or by your instructor. Carefully follow all instructions, both
written and oral. Unauthorized experiments are prohibited.
7. Safety goggles and aprons must be worn whenever you work in lab. Gloves should be worn whenever
you use chemicals that cause skin irritations or need to handle hot equipment. Wear older clothes that
cover the maximum amount of skin or wear proper lab coaats.
8. Observe good housekeeping practices. Work areas should be kept clean and tidy at all times. Bring
only your laboratory instructions, worksheets, and/or reports to the work area.
9. Know the locations and operating procedures of all safety equipment including the first aid kit,
eyewash station, safety shower, spill kit, fire extinguisher, and fire blanket. Know where the fire alarm
and the exits are located.
10. Be alert and proceed with caution at all times in the laboratory. Notify the instructor immediately of
any unsafe conditions you observe.
11. Dispose of all chemical waste properly. Never mix chemicals in sink drains. Sinks are to be used
only for water and those solutions designated by the instructor. Solid chemicals, metals, matches, filter
paper, and all other insoluble materials are to be disposed of in the proper waste containers, not in the sink.
Check the label of all waste containers twice before adding your chemical waste to the
container. Cracked or broken glass should be placed in the special container for “Broken Glass.”
12. Labels and equipment instructions must be read carefully before use. Set up and use the prescribed
apparatus as directed in the laboratory instructions provided by your instructor.
ACLaSS
PI/PD: Felix J. Seo 13. Keep hands away from your face, eyes, mouth, and body while using chemicals. Wash your hands
with soap and water after performing all experiments. Clean (with detergent powder), rinse, and dry
all work surfaces and equipment at the end of the experiment.
14. Experiments must be personally monitored at all times. You will be assigned a laboratory station at
which to work. Do not wander around the room, distract other students, or interfere with the laboratory
experiments of others.
15. Students are never permitted in the science storage rooms or preparation areas unless given specific
permission by their instructor.
16. Know what to do if there is a fire drill during a laboratory period; containers must be closed, gas
valves turned off, fume hoods turned off, and any electrical equipment turned off.
17. If you spill acid or any other corrosive chemical on you skin or clothes immediately wash area with
large amounts of water (remember that small amounts of water may be worse that no water at all). After
this get the teacher’s attention. The spill kit will be used for spills on floor or counter-top.
18. At the end of the laboratory session see that: a) main gas outlet valve is shut off b) the water is
turned off c) desk top, floor area, and sink are clean d) all equipment is cool, clean, and arranged.
Clothing
19. Any time chemicals, heat, or glassware are used, students will wear laboratory goggles. There will be
no exceptions to this rule!
20. Dress properly during a laboratory activity. Long hair, dangling jewelry, and loose or baggy
clothing are a hazard in the laboratory. Long hair must be tied back and dangling jewelry and loose or
baggy clothing must be secured. Shoes must completely cover the foot. No sandals are allowed.
Accidents and Injuries
21. Report any accident (spill, breakage, etc.) or injury (cut, burn, etc.) to the instructor immediately, no
matter how trivial it may appear.
22. If you or your lab partner are hurt, immediately get the instructor's attention. Everyone should turn
off burners and prepare to help if needed.
23. If a chemical should splash in your eye(s), immediately flush with running water from the eyewash
station for at least 20 minutes. Notify the instructor immediately.
Handling Chemicals
24. All chemicals in the laboratory are to be considered dangerous. Do not touch, taste, or smell any
chemical unless specifically instructed to do so. The proper technique for smelling chemical fumes (when
instructed to do so by the teacher) is to gently fan the air above the chemical toward your face. Breathe
normally.
ACLaSS
PI/PD: Felix J. Seo 25. Check the label on chemical bottles twice before removing any of the contents. Take only as much
chemical as you need. Smaller amounts often work better than larger amounts. Label all containers
and massing papers holding dry chemicals.
26. Never return unused chemicals to their original containers.
27. Never use mouth suction to fill a pipet. Use a pipet bulb or pipet filler.
28. Acids must be handled with extreme care. ALWAYS ADD ACID SLOWLY TO WATER, with
slow stirring and swirling, being careful of the heat produced, particularly with sulfuric acid.
29. Handle flammable hazardous liquids over a pan to contain spills. Never dispense flammable liquids
anywhere near an open flame or source of heat.
30. Never take chemicals or other materials from the laboratory area.
31. Take great care when transferring acids and other chemicals from one part of the laboratory to another.
Hold them securely and in the method demonstrated by the teacher as you walk.
Handling Glassware and Equipment
32. Inserting and removing glass tubing from rubber stoppers can be dangerous. Always lubricate
glassware (tubing, thistle tubes, thermometers, etc.) before attempting to insert it in a stopper. Always
protect your hands with towels or cotton gloves when inserting glass tubing into, or removing it from, a
rubber stopper. If a piece of glassware becomes "frozen" in a stopper, take it to your instructor for
removal.
33. When removing an electrical plug from its socket, grasp the plug, not the electrical cord. Hands must
be completely dry before touching an electrical switch, plug, or outlet.
34. Examine glassware before each use. Never use chipped or cracked glassware. Never use dirty
glassware. Do not immerse hot glassware in cold water; it may shatter.
35. Report damaged electrical equipment immediately. Look for things such as frayed cords, exposed
wires, and loose connections. Do not use damaged electrical equipment.
36. If you do not understand how to use a piece of equipment, ask the instructor for help.
Heating Substances
37. SHOULD THE BUNSEN BURNER GO OUT, IMMEDIATELY TURN OFF THE GAS AT
THE GAS OUTLET VALVE. If you wish to turn off the burner, do so by turning off the gas at the gas
outlet valve first, then close the needle valve and barrel. Never reach over an exposed flame. Light gas
burners only as instructed by the teacher.
38. Never leave a lit burner unattended. Never leave anything that is being heated or is visibly reacting
unattended. Always turn the burner or hot plate off when not in use.
ACLaSS
PI/PD: Felix J. Seo 39. You will be instructed in the proper method of heating and boiling liquids in test tubes. Do not point
the open end of a test tube being heated at yourself or anyone else.
40. Heated metals, glass, and ceramics remain very hot for a long time. They should be set aside to cool
on a trivet and then picked up with caution. Use tongs or heat-protective gloves if necessary. Determine
if an object is hot by bringing the back of your hand close to it prior to grasping it.
Fire Extinguisher
41. Fire extinguishers are classified according to a particular fire type and are given the same letter and
symbol classification as that of the fire.
Type A – combustible wood, cloth, paper, rubber, and plastics.
Type B - flammable liquids, oil, grease, and paint thinners.
Type C - energized electrical equipment
Type D - combustible metals (Mg, Ti, Na, Li, K)
Multipurpose Extinguishers are effective against types A, B, and C fires
42. To effectively operate an extinguisher, think P-A-S-S
P -- pull the pin
A-- aim the hose a the base of the fire
S – squeeze the handle
S – sweep the hose back and forth
43. Never use water on a Type B fire. These liquids float on water and, thus, water can spread the
burning liquid. Water makes hot grease splatter, and can result in burns. Cover the burning grease with
sand, baking soda, or with the metal lid of the frying pan.
44. Never use water on a Type C fire. Water can cause a severe electric shock.
ACLaSS
PI/PD: Felix J. Seo I received, read, and understood laser and electrical safety, and lab regulations and chemical
safety precaution manuals.
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