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Laser SafetyHazard Awareness This Presentation is Intended for Georgia Tech Students, Faculty and St

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Title: Laser SafetyHazard Awareness This Presentation is Intended for Georgia Tech Students, Faculty and St


1
Laser Safety/Hazard Awareness This Presentation
is Intended for Georgia Tech Students, Faculty
and Staff
2
Acknowledgements
  • Parts of this presentation were borrowed from the
    Laser Safety Training Presentation of the
    University of South Florida, North Dakota State
    University, and the Laser Safety Training
    Presentation written by Dr. Emmanuel Lafond for
    IPST.
  • Other Resources include ANSI 136.1, Safe Use of
    Lasers, and the Rockwell Laser Industries Laser
    Safety Officer Training Course Materials

3
LASER
  • Light
  • Amplification by
  • Stimulated
  • Emission of
  • Radiation

4
Terms You Will Need to Know
  • Maximum Permissible Exposure (MPE) The level of
    laser radiation to which a person may be exposed
    without hazardous effect or adverse biological
    changes in the eye or skin
  • Accessible Emission Limit (AEL)- Maximum
    accessible emission level permitted within a
    particular class
  • Nominal Hazard Zone- The space within which the
    level of the direct, reflected, or scattered
    radiation during normal operation exceeds the MPE

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7
Incandescent vs. Laser Light
  • Many wavelengths
  • Multidirectional
  • Incoherent
  • Monochromatic
  • Directional
  • Coherent

8
Characteristics of Laser Light 1
  • The light emitted from a laser is monochromatic,
    that is, it is of one color/wavelength. In
    contrast, ordinary white light is a combination
    of many colors (or wavelengths) of light.

9
Characteristics of Laser Light2
  • Lasers emit light that is highly directional,
    that is, laser light is emitted as a relatively
    narrow beam in a specific direction. Ordinary
    light, such as from a light bulb, is emitted in
    many directions away from the source.

10
Characteristics of Laser Light3
  • The light from a laser is said to be coherent,
    which means that the wavelengths of the laser
    light are in phase in space and time. Ordinary
    light can be a mixture of many wavelengths.
  • These three properties of laser light are what
    can make it more hazardous than ordinary light.
    Laser light can deposit a lot of energy within a
    small area.

11
Laser Components- Active Medium
  • A collection of atoms, molecules or ions that
    absorbs energy form an outside source and
    generates laser light by stimulated emission
  • May be a gas, a liquid (usually dyes), a solid,
    or a semi-conductor material
  • Determines the lasers characteristics, including
    wavelength

12
Laser Components- Excitation Medium
  • The energy input device
  • Gas lasers receive energy input via an electrical
    current that runs through the active medium
  • In solid state lasers, the excitation medium is
    an intense source of light, such as another laser

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WAVELENGTHS OF MOST COMMON LASERS
Wavelength (mm)
Laser Type
15
Laser Output
Time
watt (W) - Unit of power or radiant flux (1 watt
1 joule per second). Joule (J) - A unit of
energy Energy (Q) The capacity for doing work.
Energy content is commonly used to characterize
the output from pulsed lasers and is generally
expressed in Joules (J). Irradiance (E) - Power
per unit area, expressed in watts per square
centimeter.
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Laser Classification Concepts
  • Accessible radiation during normal operation (not
    service or maintenance)
  • Highest possible output
  • Relative potential hazard form the beam itself
    (not ancillary hazards)

19
Laser Classifications
  • as per ANSI Z136.1

20
Class 1
  • Not capable of presenting a hazard because of low
    power (?ltAEL) where (AELMPE x limiting aperture)
  • Generally, this means the ?W level
  • Or if a powerful laser is completely contained
    within an enclosure (embedded) (laser will not
    run if cover removed)

21
Class 2
  • Visible lasers Only
  • Natural aversion to bright light will protect the
    eye (unless a person forces himself to look into
    the beam)
  • lt1mW visible continuous wave (CW) light
  • Example- bar code scanner

22
Class 3a
  • Visible and invisible lasers
  • Maximum power 5mW for ?lt400nm or gt700nm
  • Maximum power lt5mW for ?lt400nm-700nm
  • Often have expanded beam to spread energy over a
    larger area no more than 1mw can enter a fully
    dilated pupil (7mm)

23
Class 3b
  • Visible and invisible lasers
  • May not exceed 500mW for 0.25 sec (blink)
  • May not exceed 125 mJ within an exposure time of
    lt0.25 sec.
  • Direct beam and specular reflection hazard
  • May be a diffuse reflection hazard under certain
    situations involving pulsed lasers

24
Class 4
  • Visible and Invisible
  • Any laser gt 500mW or otherwise exceeding the
    limits of a class 3b
  • Direct beam, specular reflection, and diffuse
    reflection hazard
  • Fire hazard

25
Types of Laser Hazards
  • Beam Hazards (Bioeffects)
  • Skin
  • Eye
  • Non-beam Hazards
  • Electrical
  • Chemical (Active Media dyes, gases)
  • Fire
  • Respiratory (LGACS)

26
Skin and Eye Bioeffects
  • Thermal
  • Photochemical
  • Shock wave (acoustic)
  • Ultra-short Pulses

27
Laser Tissue Interactions Thermal
  • Caused by elevated temperature after absorption
    of laser energy
  • Occurs at nearly all wavelengths

28
Laser Tissue Interactions Photochemical
  • Caused by chemical reactions within body after
    absorption of laser energy
  • Occurs only with wavelengths less than 600nm
  • Dominant effect for shorter wavelenghts for
    exposures greater than 10 seconds

29
Laser Tissue Interactions Shockwave (Acoustic)
  • An explosive effect when short pulses are
    absorbed in the retina
  • Occurs when pulse duration is less than 50
    microseconds (5x10-5 sec)

30
Laser Tissue Interactions Ultra-short Pulses
  • Self focusing increases retinal irradiance and
    minimizes energy needed for damage
  • Laser induced breakdown absorbs energy and
    shields retina

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Photochemical and Thermal Burns
  • UV can cause burns similar to sunburn. As with
    sunburn, there is an increased risk of premature
    aging of the skin and of developing skin cancer.
  • Thermal burns, up to third degree can occur with
    high power lasers (which can even set clothes on
    fire)

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Blue Light Hazard
  • Wavelengths shorter than 600 nm can cause
    photchemical damage to the retina similar to
    sunburn on the skin.
  • Unlike the skin, the retina never fully recovers
    and a permanent after image results in the
    visual field

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Ultraviolet Hazards 200-400 nM
  • Shorter wavelengths absorbed by the cornea
    resulting in a photochemical injury-
    photokeratitis aka welders flash
  • Longer wavelengths (UVA) absorbed primarily by
    the lens also result in a photochemical injury
    which is cumulative over time and results in
    cataract and cancer formations

40
Symptoms of Laser Eye Injuries
  • The site of damage depends on the wavelength of
    the incident or reflected laser beam
  • Laser light in the visible to near infrared
    spectrum (i.e., 400 - 1400 nm) can cause damage
    to the retina resulting in scotoma (blind spot in
    the fovea). This area is also know as the
    "retinal hazard region".
  • There may be difficulty in detecting blue or
    green colors secondary to cone damage, and
    pigmentation of the retina may be detected.

41
Symptoms of Laser Eye Injury
  • Photoacoustic retinal damage may be associated
    with an audible "pop" at the time of exposure.
    Visual disorientation due to retinal damage may
    not be apparent to the operator until
    considerable thermal damage has occurred.
  • Exposure to a visible laser beam can be detected
    by a bright color flash of the emitted wavelength
    and an after-image of its complementary color
    (e.g., a green 532 nm laser light would produce a
    green flash followed by a red after-image).

42
Non-Beam Hazards
  • Electrocution- the only known fatal accident
    involving lasers. Also the second most common
    laser accident after eye injuries.
  • Fire
  • Specular reflections from Class IV lasers are
    capable of starting fires when they strike walls
    or curtains that are not made out of appropriate
    materials
  • Solvents/dyes found in the lab are often flammable

43
Non-Beam Hazards
  • Chemical hazards
  • The lasing media may consist of hazardous
    chemicals. Often this in the form of a gas which
    is delivered to the laser from compressed gas
    cylinders (physical hazard)
  • Laser Generated Air Contaminants (LGACs), by
    products of cutting or ablating materials, may
    present a respiratory or dermal exposure hazard

44
Non-Beam Hazards
  • Collateral Radiation
  • A Plasma may be formed during the interaction of
    the laser an the material being treated which can
    emit broadband radiation (ionizing and
    non-ionizing).
  • High voltage power supplies may produce x-rays
  • Flash lamps for pumping the laser often emit
    strong ultraviolet light

45
Regulations
  • Occupational Safety and Health Administration-
    (OSHA)
  • Does not have a regulation but has published
    Guidelines for Laser Safety and Hazard Assessment
    STD 01-05-001
  • Enforces the ANSI Standard and will cite bad
    laser safety practices under the General Duty
    Clause 29 CFR 1910.132
  • State of Georgia
  • Requires that all Class 3b and 4 lasers are
    registered

46
Consensus Standards
  • American National Standards Institute (ANSI)
  • Has Published Z136.1 Safe Use of Lasers, most
    recent version 2006.
  • Also has Published Z136.5 Safe Use of Lasers in
    Educational Facilities for teaching labs

47
Georgia Tech Rules
  • Enforces ANSI Z136.1
  • Requires that all new (since 2002) installations
    and re-installations of class 3b or 4 lasers be
    Z136.1 compliant
  • Exceptions to the Z136.1 requirements can be
    made, but only with the approval of the GT LSO

48
Hazard Control Measures
  • Engineering Controls
  • Protective housings
  • Walls and curtains
  • Interlocks on room doors (Class 3b 4)
  • Key Control Master switch (Class 3b 4)
  • Beam stop or attenuator (Class 3b 4)
  • Ventilation for LGACS/chemical hazards

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Hazard Control Measures
  • Administrative
  • Warning signs and labels
  • Standard Operating Procedures (SOPs)
  • Laser Set Up

51
Manufacturers Labels
52
Warning Signs
  • All rooms with class 3a, 3b, or 4 lasers must
    have appropriate warning signs at all entrances

53
Warning Sign for Class 2 and Class 3a Lasers
  • do not exceed MPE

54
Warning Sign for Class 3a, 3b, and 4 Lasers
  • 3a that exceed MPE, All 3b and 4

55
Temporary Sign for Laser Repairs When Interlocks
Must be Defeated
56
Set Up
  • Golden Rule of Laser Safety Never situate a
    laser so a to put the beam at eye level (standing
    or seated)

57
Standard Operating Procedures
  • Required for all class 3b and 4 lasers
  • Consist of a step by step procedure for operating
    each laser
  • Includes all safety precautions
  • Separate SOPs for aligning or servicing the
    laser
  • Or just a line that says this laser will be
    sent back to the factory for servicing

58
Personal Protective Equipment
  • Eyes
  • Skin
  • Respiratory

59
Personal Protective Equipment Glasses and
Goggles
  • Laser goggles
  • Should also provide side protection
  • Are intended for long term indirect viewing or
    short term (accidental) direct viewing
  • Will not provide protection for direct beam
    viewing (gt10sec), they will burn or melt

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Respiratory Protection
  • Laser procedures with the potential for
    generating LGACs must be designed to include
    exhaust ventilation
  • When exhaust ventilation is not feasible, the GT
    Chemical Safety Coordinator must be contacted to
    do a respiratory hazard assessment, and, if
    necessary, initiate the appropriate steps to
    include the lab users in the GT Respiratory
    Protection Program
  • Lab users may not initiate the use of respirators
    on their own.

63
Medical Surveillance
  • Consists of a baseline eye exam and an exit eye
    exam.
  • Not currently required by GT, may be required by
    your program/department

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Responsibilities
  • Laser Safety Officer- classify or verify
    classification of lasers perform hazard
    evaluations, ensures that the prescribed control
    measures are in effect, approves SOPs, recommends
    protective equipment, reviews new lab
    construction plans, laser installation, performs
    periodic safety audits.

67
Responsibilities
  • Laser System Supervisor- Usually the PI or the
    owner of the laser, responsible for informing
    the LSO before setting up or relocating existing
    class 3b or 4 lasers or before acquiring new
    class 3b or 4 lasers ensuring that SOPs are
    approved and in place before operating any class
    3b or 4 laser for ensuring that all faculty,
    staff, and students using the laser are trained
    in its use and hazards keeps a list of all
    authorized users.

68
Responsibilities
  • Laser System Operator
  • Responsible for the safety of themselves and
    anyone else in the area of the laser during
    operation for reviewing and following
    established SOPs for using all prescribed PPE
    for reporting accidents and near-misses to the
    Laser System Supervisor.
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