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Laser Safety Training

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Eyewear Labeling. Eyewear is labeled with the optical density at a ... Laser Eyewear in suspicious condition should be disposed of. 23. Alignment Goggles ... – PowerPoint PPT presentation

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Title: Laser Safety Training


1
  • Laser Safety Training
  • Department of Occupational Health Safety
  • Richard Grundsten, P.Eng.
  • Laser Safety Officer
  • June 2009
  • email rgsten_at_yorku.ca

2
Legislation
  • The OHS Act requires employers to inform workers
    about the hazards of physical agents (e.g. laser
    radiation).
  • American Standard for Safe Use of Lasers provides
    provides recommendations for safe use.
  • Manufacturers must certify their lasers according
    to the ANSI standard.

3
Contents of Laser Safety Program
  • Laser Safety Training
  • Inventory of Class 3b 4 lasers
  • Inspections of Class 3b 4 lasers
  • Personal Protective equipment
  • Engineering controls
  • Standard Operating Procedures

4
Laser Classification
  • Laser classification is based on the damaging
    effects of the laser beam on the eyes and skin.
  • Non-beam hazards are not considered in the
    classification.

5
Direct Intrabeam Viewing
6
Specular Intrabeam Viewing
E.g. Mirror
7
Diffuse Reflected Viewing
8
Class 1 Lasers (Exempt)
  • Not capable of producing damaging radiation
    levels during normal operation.
  • E.g. Laser printer, CD-Rom
  • Does not apply to servicing.

9
Class 2 3a Lasers (Low Power)
  • Class 2 lasers emit visible light. Not hazardous
    if viewed less than 0.25 second. Maximum power is
    1 mW for CW lasers. Eg. Barcode Scanner.
  • Class 3a lasers probably not hazardous if viewed
    within 0.25 seconds. Hazardous if viewed with
    collecting optics. Maximum power is 5mW. Some
    require DANGER labels. E.g. Laser Pointer.

10
Class 3b Lasers (Medium Power)
  • Hazardous if viewed directly or by specular
    reflection. Diffuse reflection not usually
    hazardous. Upper limit is 0.5W for CW lasers.

11
Class 4 lasers (high power)
  • Lasers exceeding 0.5W
  • Hazardous under all viewing conditions direct,
    specular and diffuse.
  • Potential fire hazard when in contact with
    combustible materials
  • Produce skin hazards from ultraviolet radiation.
  • Can produce laser generated air contaminants and
    hazardous plasma radiation.

12
Visible and Near-Infrared Radiation causes
Retinal burn
13
Mid and Far Infrared - causes damage to the
cornea by increased temperature in
tears and tissue water. Mid Ultraviolet causes
photokeratitis (welders flash)
Mid
14
Near Ultraviolet Contributes to certain forms
of cataracts Xenon Chloride Excimer Instant
cataract, 308 nm pulsed laser
15
Skin Hazards
  • UV-A Photosensitive reactions tanning
  • UV-B IR Sun burn (1000 x sensitive than UV-A
    to burns)
  • UV-C Skin burn (sunburns without tanning, not
    from sun)
  • Skin cancer and accelerated skin aging

16
Skin Hazards
17
Most Common Laser Accidents
  • Exposure during alignment -most frequent cause
  • Misaligned optics and stray beams
  • Improper methods of handling high voltage
  • Use of incorrect eyewear or eyewear failure
  • Improper restoration of equipment after service
  • Inhalation of laser generated materials

18
Laser Accidents
  • NdYAG 25.8
  • Argon 17.2
  • C02 11.9
  • Others 45.1

19
Type of Accidents
  • Eye exposure -73
  • Skin exposure -13.9
  • Fire -7.3
  • Electrical Shock -3.6 (5 deaths)
  • Note Contact DOHS to arrange a course in CPR.

20
Laser Eye Protection
  • Required when engineering or administrative
    controls do not eliminate potential exposure.
  • Must be enforced for Class 4 lasers.
  • Should be enforced for Class 3b lasers.

21
Eyewear Labeling
  • Eyewear is labeled with the optical density at a
    specified wavelength.
  • Many lasers radiate at than one wavelength thus
    one set of protective eyewear may not be
    appropriate.
  • Indirect viewing maybe more appropriate when
    using lasers that are tunable over broad
    wavelength bands.
  • In multi-laser environments colour coding or
    other identification methods of laser eyewear is
    recommended.

22
Cleaning and Inspecting Laser Eyewear
  • Laser eyewear must be cleaned and inspected
    regularly.
  • Laser Eyewear in suspicious condition should be
    disposed of.

23
Alignment Goggles
  • Full protection goggles can make the beam
    invisible.
  • Therefore users often perform alignments without
    protection.
  • Alignment goggles let users view the beam safely.
    Users are protected by the blink response.
  • Alignment goggles are only useful for visible
    lasers

24
Enclosed Beam
  • Enclosing the laser beam is the preferred control
    measure to class 3b or 4 lasers.
  • This meets the requirements for a Class 1 laser
    and can be operated with no others controls.

25
Limited open beam
  • A laser beam confined to a limited area greatly
    reduces the risk of potential exposure.
  • In this case a detailed written standard
    operating procedure (SOP) is sufficient.
  • The following list of measures should be used
    when total beam enclosure is not possible
  • Enclose the beam as much as possible, where
    access is not necessary.
  • Use beam dumps, barriers, shields, blocks,
    baffles, etc. to block stray beams due to
    reflections from mirrors, prisms, and other
    optical components.
  • Use dark, absorbing, diffuse and fire-resistant
    materials for these purposes.
  • Be aware that some surfaces can act like mirrors
    for C02 lasers even though they are black and
    visibly dull.
  • Ensure barriers used are able to withstand direct
    and diffusely scattered beams and do not support
    combustion or release toxic fumes when exposed
    laser beams.

26
Totally Open Beam Path
  • Hazard analysis and Nominal Hazard Zone (NHZ)
    assessment is required.
  • The NHZ is the area in which the laser light is
    hazardous to the eye or skin.
  • When optical layouts change often the
    re-evaluation of the NHZ can become tedious.
    Therefore it maybe easier to assume the entire
    laser laboratory area as the NHZ.
  • In this situation all the requirements of a laser
    controlled area will apply to the laboratory.

27
Without Protective Housing E.g. Servicing the
Laser
  • If the protective housing must be removed the
    following controls may be necessary
  • Eye protection
  • Area controls
  • Barrier, shrouds, beam stops, etc.
  • Procedural controls
  • Education and training

28
Laser Controlled Area for Class 3b and 4 Lasers
  • When the beam path is not enclosed a laser
    controlled area must be established involving the
    following
  • A warning sign must be posted at the entryway
    and, if necessary, within the laser controlled
    area.
  • Laser operated by trained personnel only.
  • Beam path must be limited to the controlled area.

29
Controls recommended for Class 3b required for
Class 4
  • Direct supervision of an individual knowledgeable
    in laser safety.
  • Ensure that access by spectators is limited and
    requires approval.
  • Any potentially hazardous beam must be terminated
    in a beam stop made of appropriate material.
  • When possible use only diffusely reflecting
    materials in or near the beam path. Avoid use of
    reflective materials near the beam paths. If such
    materials are present use of shields.
  • Personnel within the laser controlled area must
    be provided with the appropriate eye protection.

30
Controls recommended for Class 3b required for
Class 4 (cont)
  • Ensure the laser beam is not at eye level of any
    person working in the lab.
  • All windows or doorways inside a room must be
    covered to reduce the transmitted laser radiation
    to safe levels.
  • Laser must be stored or disabled (for example,
    removal of the key) laser when not in use. 1000
    fine in USA if key left in a laser not being used.

31
Controls Required for Class 4 Lasers
  • Ensure an accessible evacuation path exist in the
    event of an emergency.
  • Must have a Panic Button (switch or equivalent
    device) to quickly deactivate the laser or reduce
    the output to safe levels.

32
Controls required for Class 4 lasers (Cont)
  • Must use one of the following three options
  • (i) Non-Defeatable Controls. Interlocks that
    reduce the output to safe levels when the door to
    the room is opened.
  • (ii) Defeatable Controls. If there is no laser
    hazard at the entryway and in cases where it is
    necessary to keep the laser operating such as
    with long term testing or surgery.

33
Controls required for Class 4 lasers (Cont)
  • (iii)Procedural Controls. When door interlocks
    are not feasible, the following procedural
    controls apply
  • A door, blocking barrier, screen, curtains, etc.
    must be used to block or attenuate the laser beam
    at the entryway to ensure that laser radiation
    outside the area does not exceed MPE, nor anyone
    gets exposed above the MPE immediately upon
    entry.
  • A warning light or sound at the entryway
    indicating when the laser is energizing and
    operating. A lighted warning or flashing light
    are examples of this requirement.

34
Other Beam Control Guidelines
  • Secure mounts to table and optical components in
    their holders to prevent stray reflections from
    misaligned optics.
  • Do not use flammable materials to trace beam
    paths or for stopping Class 4 laser beams.
  • Use remote firing and monitoring of the beam
    where possible.
  • For many applications it is possible to use
    relatively inexpensive digital (CCD) cameras.

35
Other Beam Control Guidelines
  • Use low power visible lasers for alignments of
    high powered visible and invisible lasers.
  • Use beam shutters, filters or attenuators to
    reduce the beam power to safer levels whenever
    full beam power is not required.

36
Standard Operating Procedures (SOPs)
  • Written SOP for alignment procedures are
    recommended for Class 3b and required for Class 4
    laser. For example the use of low power visible
    alignment lasers for path simulation of class 3b
    or 4 lasers or the wearing of alignment goggles.
  • Protective equipment. When other control
    measures are inadequate to eliminate the
    possibility for hazardous eye or skin exposure,
    use of protective equipment may be required.
    Protective equipment generally means goggles or
    spectacles, barriers, windows, clothing and
    gloves and other devices specifically selected
    for protection against laser radiation.

37
Warning Sign for Class 3b, 4 and Certain 3a Lasers
  • Position 1 Precautionary Statements
  • Laser RadiationAvoid Eye and Skin Exposure to
    Direct and Scattered Radiation
  • Knock before Entering or
  • Do Not Enter When Light is On
  • Position 2 - Type of laser
  • Wavelength, pulsed duration (if appropriate) and
    maximum output power or energy
  • Position 3 - The Class of the laser

1
2
3
38
Temporary Laser Controlled Area (E.g. Servicing
Laser)
  • If a temporary laser controlled area is
    established, as in the case of servicing a laser
    a notice sign for temporary laser controlled area
    must be posted.

39
  • Section 6
  • Non-beam Hazards

40
Electrical Hazards
  • When possible have the laser connected by a
    qualified electrician and verify that the laser
    is properly grounded. Work in pairs while
    servicing the laser or if working after hours.
  • Request that at least one member of the group is
    trained in CPR. Be familiar with rescue
    procedures in case of an electrical shock.
  • Remove excessive wires/cables from the floor.

41
Electrical Hazards (Cont)
  • 4. Do not wear rings and other metallic objects
    when working with electrical equipment.
  • Do not handle electrical equipment when hands,
    feet or body are wet, perspiring or when floor is
    wet. Stand on dry insulating rubber mat.
  • 6. Lock-out and tag any electrical switch when
    servicing electrical equipment.

42
Electrical Hazards (Cont)
  • Components such as capacitors carry a lethal
    charge even after the main power has been
    disconnected.
  • These must be safely discharged by grounding
    (e.g. use a grounding strap).
  • When possible work with one hand to avoid
    becoming part of the circuit.
  • Review the manual to identify any components that
    have high voltage.

43
Collateral and Plasma Radiation
  • Measures must be taken to prevent exposure to
    collateral radiation such as X-rays generated by
    High Voltage (gt15kV)
  • Ultraviolet and visible radiation maybe generated
    during laser material interactions as well as
    from some laser discharge tubes and pumping
    lamps.

44
Fire Hazards
  • Class 4 lasers represent a fire hazard. To
    reduce risk of fire, keep flammable materials
    away from open beams. If unprotected plastic
    tubing or wire insulation is present in vicinity
    of beam paths, it must be appropriately shielded
    using non-flammable materials to protect from
    potential exposure to the beam.
  • 2. Fire extinguishers should be used for small
    fires only, if the fire can be put down safely
    with one extinguisher. Be familiar with the
    location of the extinguishers and the first aid
    kits. Report the fire to the University fire
    protection service.

45
Chemical/Gas Cylinder Hazards
  • Compressed gases must be secured to a wall or
    other fixed object. Move cylinders with the
    cylinder carts and vent any toxic gases.
  • Laser dyes must be labeled and stored adequately.
    Fume hoods must be used for dye mixing. Use of
    containers for the circulator pumps is
    recommended.
  • Laser Generated Air Contaminants -Proper exhaust
    ventilation or respiratory protection must be
    used when lasers are used for material processing
    (cutting, marking, welding, etc.) or interaction
    with tissues.

46
Other Non-beam Hazards
  • Explosion hazards (e.g. when heat is not
    dissipated quickly as with pulsed lasers)
  • Noise Ear protection maybe required (if you
    have to raise your voice to be heard)
  • Ergonomics Avoid tripping hazards, organize lab
    in order to move around safely.

47
Quiz
  • To complete the refresher training, complete the
    quiz http//www.yorku.ca/dohs/documents/Laser_Safe
    ty_Quiz.doc and send it to
  • Richard Grundsten
  • Department of Occupational Heath and Safety
  • East Office Building, Room C37
  • DOHS will inform you of the test results.
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