McGill University Laser Safety Course Environmental Health & Safety Instructor: Joseph Vincelli joseph.vincelli@mcgill.ca Version: Sept 24, 2010 1 Agenda / Course Content Agenda: Lecture 3.0 hrs & Quiz 0.5 hr Course Content: McGill Laser Safety Policy & Program Procedures & responsibilities Fundamentals of laser operation Laser hazards & bioeffects. Laser classifications Control measures Non-beam hazards Medical examinations & emergency procedures 2 McGill University Laser Safety Policy According Health & Safety Policies & the Quebec Occupational Health & Safety Act Intended to assist in the effective control of laser hazards Based on ANSI Z136.1-2007 Covers only Class 3B and 4 lasers Applies to all personnel working with or near lasers Applies to all departments or University affiliated sites 3 1
McGill University Laser Safety Program Laser safety under the ULSC, designated LSO Responsibilities for different personnel Registration of lasers Laboratory laser safety inspections Education and training Baseline eye examinations Control measures Reporting of incidents and program reviews 4 McGill University Laser Safety Program Implementation relies on Faculty members Principle Investigator (PI) - ultimately responsible for the safe use of lasers PI is responsible that all type of personnel is trained (exception: visitors or spectators) Visitors are persons who wish to observe a laser in operation permission from the PI required degree of hazard, avoidance procedure must be explained appropriate protective measures to be taken 5 Levels of Responsibilities Registration of lasers: PI, LSO Laser Safety Inspections: EHS, LSO Education and Training: PI to ensure that personnel is trained by EHS or other Baseline examination: EHS, LSO 6 2
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Basic Definitions Laser: light amplification by stimulated emission of radiation Laser device: a device which produces an intense, coherent and directional beam of monochromatic light (1 wavelength or color) by stimulating electronic transitions to low energy levels Laser system: assembly of 1 or more lasers Laser classification: number increases with beam hazard Embedded laser: enclosed laser that lowers the laser hazard Diffuse reflection: beam is reflected in many directions & changes spatial distribution Specular reflection: a mirror-like reflection and no change in beam spatial distribution 10 Specular & Diffuse reflections Incident Light Specularly Reflected Light Incident Light Diffusely Reflected Light Visibly rough surface may produce specular reflections at longer wavelengths (CO 2 laser at 10.6 μm) 11 Basic Definitions Maximum Permissible Exposure (MPE) The level of laser radiation to which, an unprotected person may be exposed without adverse biological changes in the eye or skin. Nominal Hazard Zone (NHZ) The space within which direct, reflected, or scattered radiation may exceed the applicable MPE. Exposure levels beyond the boundary of the NHZ are within the MPE. Aversion Response: is the closing of the eyelid or movement of the head to avoid exposure to bright light or visible laser wavelengths and occur with 0.25 second. 12 4
Laser Components Lasers require 3 components to operate: Active medium With wavelength determines the laser beam s output (i.e. solid or semi-solid material, dye or gas) Excitation mechanism Input energy device (i.e. an intense light or electrical current ) Optical resonator 2 specially designed mirror opposed to each other resulting in the beam output 13 Laser Components-Visual Example Energy (excitation) source Active (amplifying or gain) medium Emerging Laser Beam High reflection mirror Optical Resonator (laser cavity) Partial reflection mirror 14 Laser Categories Lasers are classified by active medium, wavelength, & maximum output power Lasers are characterized by their active medium: Solid Solid state Semi conductor (diode) Liquid (Dye) Gas 15 5
Laser Categories - Solids Solid state lasers: Optically clear materials such as glass or host crystal Ruby laser, Nd:YAG (neodymium: yttrium/aluminum/garnet) laser Operate as continuous wave (CW) or pulse mode Semi conductor (diode) lasers: Most common laser composed of 3 families of diode lasers: GaAlAs (gallium/aluminum/arsenide) from 750 to 950 nm used in CD & CD/ROM players InGaASP (Indium/gallium/arsenide/phosphide) from 1100 to 1650 nm used in optical telecommunications AlGaInP (aluminum/gallium/arsenide/phosphide) operates in the visible spectrum, primarily red 16 Laser Construction Solid state laser (e.g. Nd:YAG) Energy (excitation) source Active (amplifying or gain) medium Emerging Laser Beam High reflection mirror Optical Resonator (laser cavity) Partial reflection mirror 17 Laser Construction Semiconductor (diode) laser Current Lead + Active Region Polished Face (mirror) Lead Polished Face 18 6
Laser Categories Liquids & Gases Liquid (dye) lasers: Use a flowing dye as the active medium Operate either as pulse or CW mode Example: Argon laser Gas lasers Examples: HeNe (helium-neon) laser, CO 2 (carbon dioxide) laser, and Ar (argon) laser Operate in CW Excimer ( excited dimer ) lasers like XeCl (xenon-chloride) laser, function in ultraviolet spectrum & operate in the pulse mode 19 Laser Construction Gas laser (e.g. He-Ne, Argon, CO 2 ) ELECTRICAL DISCHARGE Cathode Anode Mirror Tube Partial Mirror 20 Copyright 2005 Laser Institute of America Laser Categories By wavelength Common Laser classifications by wavelength 21 7
Modes of Operation Continuous wave (CW) Pulsed mode Q-switched (~10-250 ns) Single pulses Repetitively pulsed Scanning (1D or 2D) Combinations of modes Ultra-short (femtosecond) pulses (10-15 sec) 22 Is anything wrong on this picture? 23 Laser Hazards Beam Exposure (radiation hazards) Associated Hazards (non-beam) Direct beam Specular reflections Diffuse reflections Eye hazards Skin hazards Many types hazards 24 8
Eye Hazards Simplified Schematic of the Human Eye Sclera Ciliary muscle Choroid Cornea Iris Retina Fovea Visual axis Aqueous humor Lens Optic nerve Vitreous humor 25 Eye Hazards Retinal Hazard Range 400 nm to 1400 nm Visible and near infrared radiation is transmitted through and focused on the retina 26 27 9
Absorption of optical radiation by the human eye UVB and UVC (180-315 nm) and Far IR and Mid IR (1400 nm to 1 mm) Visible (400 700 nm) and Near IR (700 1400 nm) UVA (315 400 nm) UV damage at the cornea IR damage at the retina UV damage at the cornea 28 Summary of bioeffects on the eye and skin 29 Non-Beam hazards Electrical Fire Ancillary radiation (other radiation hazards) Explosion Compressed gases, cryogenics Laser Generated Air Contaminants Noise, confined space, robotics (crushing) 30 10
Laser Classifications Class 1: Generally safe during operation Incapable of producing eye injury Low emission levels or beam completely enclosed Exempt from control measures or surveillance Class 1M: Safe for the naked eye during operation Only concern: optically aided viewing 31 Laser Classifications Class 2: Visible wavelengths only (0.4 to 0.7 μm) Eye protected by the aversion response (0.25 s) Maximum CW output: 1 mw Class 2M: (low power) Visible wavelengths only (0.4 to 0.7 μm) Naked eye protected by the aversion response (0.25 s) Potentially hazardous if viewed with optical aids 32 Laser Classifications Class 3R: (replaced the 3A) Potentially hazardous direct viewing Probability of actual injury is small Not a diffuse reflection hazard Maximum visible CW power 5 mw Class 3B: May be hazardous for direct and specular reflection Normally not a diffuse reflection or fire hazard Maximum CW power 500 mw 33 11
Laser Classifications Class 4: Hazard to the eye and skin From direct beam, specular and diffuse reflections Fire hazard LGACs respiratory hazards Hazardous plasma radiation CW power > 500 mw LGACs = laser-generated air contaminants 34 Laser Accidents Potential Causes Conditions associated with laser accidents: 1. Unanticipated eye/skin exposure during alignment 2. Misaligned optics and upwardly directed beams 3. Available eye protection not used 4. Equipment malfunction 5. Improper methods of handling high voltage 6. Intentional exposure of unprotected personnel 7. Operators unfamiliar with laser equipment 8. Lack of protection for non-beam hazards 9. Improper restoration of equipment after service 10. Use of eyewear not appropriate for laser in use 11. Inhalation of laser-generated air contaminants 12. Fires resulting from ignition of materials 13. Failure to follow Standard Operating Procedures (SOP) 35 Where is the laser? 36 12
Specifics of Laser Use in Research Various and changing applications Multiple lasers and/or multiple users in same area Experimental work, prototypes, pushing the limits Presence of not involved personnel Frequent modifications and/or alignment Large number of optical components Beam enclosures and interlocking - rarely feasible Heavy reliance on safety goggles No specific budget for laser safety Experienced researchers may inadequately train new researchers to deal with laser hazards and/or laser safety practices Lack of centralized control on new laser purchasing Researchers simply may be unaware about the laser safety program 37 A typical laser laboratory 38 High Risk Laser Scenarios Laser system requiring frequent alignment Many optical components Access to a high power open beam Different operators using the same laser system Same laser used for different applications Several lasers used within the same lab Laser service, repair, alignment, testing Experimental use or building of prototypes Outdoor use Inadequate training Safety goggles considered as the only protection measure 39 13
Approach to Control Measures To reduce the possibility of eye/skin exposure Prescribed according to classification Approved, monitored and enforced by LSO Minimum laser radiation sufficient for the application Beam height not at eye level! Engineering controls primary consideration Enclosure preferred method of control If engineering controls impractical or inadequate administrative and procedural controls and PPE Embedded lasers what is the class of the enclosed laser LSO: may request additional safety instructions for special use 40 Control Measures for Specific Operations Class 3B and 4 lasers require supervised operation Laser operator needs to maintain visual control Visual contact necessary to terminate operations in case of malfunction or unsafe conditions arise Unsupervised operations granted if accessible levels are < MPE by control measures 41 Control Measures for Unattended Use Unattended use of Class 3B/4 lasers only permitted when: LSO has implemented adequate control measures and laser safety training to those who may enter the area the area is posted with a DANGER sign the sign contains appropriate instructions regarding the hazards of entry into the area 42 14
LEGEND NR NHZ MPE LSO No requirement Nominal Hazard Zone analysis required Required if MPE is exceeded Alternative Controls to be established by the Laser Safety Officer 43 User-Built Enclosures 44 User-Built Enclosures 45 15
Enclosure provided by manufacturer 46 Partial beam enclosure 47 Curtain 48 16
Beam path between enclosures 49 Side shield / desk 50 Side shield 51 17
Corner shrouds 52 Sample warning signs for Class 3B and 4 lasers emitting visible radiation 53 Sample warning signs for Class 3B and 4 lasers emitting invisible radiation 54 18
Sample warning signs for Class 3B and 4 lasers emitting visible and invisible radiation 55 Sample sign for a Temporary Laser Controlled Area during service (Class 4 embedded laser) 56 Laser Controlled Area Controlled access by trained personnel Posted with warning signs outside and within the area Beam path is well defined Well defined & controlled if laser beam extends outdoor Supervision by an individual knowledgeable in laser safety Access by spectators (visitors) is limited and requires approval 57 19
Laser Controlled Area - Continued Potentially hazardous beam properly terminated Only diffuse materials near the beam (where feasible) Personnel provided with appropriate eye protection Exposed beam path - above or below eye level Windows, doors, etc. covered or restricted so laser < MPE Disable laser when not in use to prevent unauthorized use Emergency Stop installed if necessary 58 Laser Controlled Area - Continued Entryway Controls: Quick exit at all times in case of emergency Non-defeatable (non-override) Safety Controls Procedural Safety Controls: Authorized personnel is trained and adequate PPE provided A blocking barrier to screen the laser radiation at the entryway An activation warning (light or sound) indicates that laser is operates at Class 4 levels 59 60 20
61 Barriers 62 Entryway controls Activation warning signage 1 st example 63 21
Entryway controls Activation warning light 2 nd example 64 Activation warning signage with curtain 65 Entryway controls Activation warning signage with procedures 66 22
Entryway controls Using curtain 67 Door signs with procedures With proper info on laser type, wavelength, output power, & pulse energy 68 Outdoor Use of Lasers NHZ evaluation is required including all possible beam directions Use of optical aids to be considered Exposure levels << MPE may be of concern (50 nw/cm 2 ) Lasers in navigable airspace: Canada: NAVCAN, Transport Canada, Health Canada US: FAA, Space Command 69 23
Administrative & Procedural Controls Engineering controls - primary consideration When impractical or inadequate administrative and procedural controls personal protective equipment Include methods or instructions which specify rules or work practices May specify the use of personal protective equipment. Normally apply to Class 3B and 4 lasers 70 LEGEND NHZ LSO MPE Nominal Hazard Zone analysis required To be determined by the Laser Safety Officer Required if MPE is exceeded 71 Administrative & Procedural Controls for Alignment Procedures Alignment Procedures A temporary beam attenuator to reduce the level < MPE Written alignment methods Use of low power visible lasers Only by those who have received laser safety training Exclude unnecessary personnel from the area Wear protective eyewear and clothing Use beam viewers or other devices Use the laser shutter 72 24
Administrative & Procedural Controls for Alignment - Continued Alignment Procedures Beam stop to terminate high power beams Barriers to block potential stray beams Beam blocks behind optics (e.g. mirrors) Block stray reflections before proceeding to next component Assure beams and reflections are terminated before high power operation Post with appropriate area warning sign 73 Administrative & Procedural Controls for Laser Demonstrations Laser Demonstrations Involving the General Public Require special control measures that are different in nature Limitation of exposure and access to invisible laser radiation Safety considerations for operators and performers Emission prevention in case of failure of scanning devices Unsupervised installations specific vertical and lateral separation distance requirements 74 Administrative & Procedural Controls for Laser Demos - Continued Laser Demonstrations Involving the General Public Supervised laser installations visual access by operator and distance considerations Beam termination in case of malfunction, audience unruliness, or other unsafe conditions Maximum power limitations Posting of warning signs and logos Compliance with federal, provincial or local (e.g. municipal) requirements. 75 25
Administrative & Procedural Controls for LOFTS Laser Optical Fiber Transmission Systems Enclosed systems Requirements for LOFTS are normally different If accessible radiation when disconnected < MPE by engineering controls then an uncontrolled area & no other controls needed If accessible radiation > MPE: - during operation controlled area - during maintenance or service temporary controlled area - fibers attached to laser not to be disconnected before termination of the beam into the fiber - connector to bear a label Hazardous Laser Radiation when Disconnected - Procedures for broken/loose fibers (lock/tag at laser) need to be initiated 76 Administrative & Procedural Controls for Laser Robotics Laser Robotic Installations robot envelope should include the laser NHZ where beam is focused, safeguards can be guaranteed if: - design or control measures in combination provide positive beam termination - beam geometry is limited to only necessary task - workers located at a distance >= lens-on-laser NHZ 77 What is wrong? 78 26
PE & PPE Protective Equipment (PE) & Personal Protective Equipment (PPE) Enclosure of laser or beam - preferred method When other controls inadequate, use of PE & PPE may be necessary Goggles, safety glasses, face shields, barriers, windows, clothing, gloves, etc. PPE may have serious limitations if the only control used PPE may not adequately reduce/eliminate hazard PPE may be damaged by the laser radiation. 79 When to use protective eyewear? 80 PPE - Eyewear Eye protection should be required and enforced for Class 3B must be required and enforced for Class 4 PI responsible that PPE is available and worn in NHZ PI must assure that PPE is labeled with the OD & λ info Color coding or other identification recommended in multi-laser environments 81 27
PPE - Continued PPE must withstand direct or scattered beams as intended Damage threshold is typically for a 10 seconds duration Damage threshold not to be exceeded in the worst case scenarios Request test data from manufacturers to confirm suitability PPE must be periodically cleaned and inspected Suspicious eyewear should be tested & discarded or replaced. 82 PPE for UV lasers UV Laser Protection UV requires particular care (cumulative, eye/skin) Both eye and skin protection Face shields & clothing in addition to protective eyewear Specific UV wavelengths! PPE must be used with open Class 3B or 4 UV lasers 83 Protective Eyewear & OD Optical Density (OD) measure of absorption (or transmission) of a material wavelength dependent OD = log 10 (1/T λ ) = log 10 (Hp /MPE) T λ = transmittance Hp = potential laser exposure (e.g. irradiance) Hp and MPE: same units! 84 28
85 Protective Eyewear & OD - Continued OD and wavelengths must be specified Many lasers emit more than a single wavelength PPE designed for a particular wavelength, may have inadequate OD at another wavelength from the same laser. Particularly serious with tunable lasers Alternative solution, use TV cameras 86 PPE Skin Protection Skin Protection In applications where UV excimer lasers are used A must if repeated/long term exposures are anticipated Potentially damaging skin exposure possible at UVs of 295-400 nm Controls best achieved by engineering controls Or use skin-covers and/or sun screen creams Most gloves provide some protection Tightly woven fabrics made for laboratory jackets and coats with opaque gloves are best 87 29
88 Protective Equipment - Other Types Other Protective Equipment May be required whenever engineering controls cannot provide protection from a harmful environment: Respirators Local exhaust ventilation Fire extinguishers Hearing protection, etc. 89 Review of Common Laser Deficiencies Just Not looking at beam often considered sufficient Open beams at eye levels Poor beam management (open, reflections, stops) Eyewear considered before engineering controls Disabled interlocks and/or removed protective covers No manual, no SOP for operation/alignment Access by non-authorized personnel Missing or inadequate warning signs/labels Inadequate entryway controls, and no indication of laser operation 90 30
Review of Common Laser Deficiencies Continued MPE unknown, NHZ not determined Key not removed when laser not in use Safety practices as oral instructions only (do and don t) No emergency stop No skin protection from UV Improper eyewear (markings, damaged, mixed with others) Flammable or reflective materials near Class 4 beams No protection from non-beam hazards 91 Is this warning sign sufficient? 92 Is this a warning sign? 93 31
Which warning label is correct? 94 What is missing? Laser type?, Wavelength Range?, Maximum Output Power?, Maximum Pulse Energy? 95 What is wrong here? 96 32
Is this an adequate enclosure? 97 Is the open beam necessary? 98 Non-Beam Hazards Do not result from direct exposure to the laser beam Physical, chemical, and biological considerations May occur when: materials exposed lead to fire or airborne contaminants laser generation materials (e.g. gases or dyes) are released into the air, or contact with components (e.g. shock or electrocution). Can be life threatening (electrocution) Control measures are different from laser beam controls Written SOPs must also address non-beam hazards 99 33
Non-Beam Hazards Physical Agents Electrical hazards Electric shock Resistive heating Spark ignition of flammable materials Ionizing & Non-ionizing Radiation X ray-radiation from high-voltage vacuum tubes (>15 kv), or lasermetal induced plasmas Ultraviolet (UV) and visible from laser-matter interactions with targets Electric, Magnetic or Electromagnetic Fields maybe generated and pose an exposure risk 100 Physical Agents -Continued Fire Hazards Class 4 Wires, plastic tubing, flammable components Invisible wavelengths special concern Open beams easily misaligned Explosion Hazards High-pressure arc lamps, filament lamps, and capacitor banks Explosive chemical reactions Target and optical elements may shatter (when contaminated) Enclosing, shielding or other measures maybe required Noise Noise control may be required for certain lasers (e.g. pulsed excimer lasers) TWA-TLV: ACGIH (85 dba for 8 hrs) or Quebec Standard (90 dba for 8 hrs) will apply 101 Mechanical Hazards of Robotics Robots can: punch holes in protective housing damage beam delivery system aim laser beam at operators or enclosure Mechanical safety considerations: worker pinned between robot and object ( pinch effect ) worker injured by moving parts of the robotic system Control measures may include: Surface interlock mats Interlock light curtains Non-rigid walls and barriers 102 34
Non-Beam Hazards - Chemical Agents MSDS required for all chemicals Workers must have completed a WHMIS course Gases can be exhausted by lasers and produced by targets Proper ventilation required to reduce exposure levels For further information contact EHS 103 Chemical Agents - LGAC Laser Generated Airborne Contaminants (LGAC) Plastics, composites, metals, and tissues may produce carcinogenic, toxic and noxious airborne contaminants Some materials will burn and/or create hazardous airborne contaminants (i.e. dust, smoke, vapor, etc.) Exposure to LGAC should be controlled 104 Chemical Agents Compressed Gases Compressed Gases Hazardous gases - Exhaust cabinets with sensors SOP for safe handling Commonly found with laser dyes and solvents Control measures should reduce the gas concentration Examples include: ventilation, isolation, respiratory protection, gas sensors & alarms 105 35
Example of an Exhaust Cabinet 106 Non-Beam Hazards Biological LGAC Biological Agents LGAC may include infectious materials LGAC may be generated when laser interact with tissue Bacteria and viruses may survive beam irradiation and become airborne 107 Non-Beam Hazards Human Factors Human Factors Ergonomics Glare, startle reactions, afterimages and temporary flash blindness Reported as distractions leading to other problems LSO should be aware that these issues may create visual distractions Limited Work Space Problem near mechanical or high voltage equipment Room needed to work and maneuver comfortably Bigger problem, when more than one laser is in operation Wires and cables on the floor (can lead to Trip & Fall Hazards) Local exhaust, ventilation & respiratory protection maybe needed if LGACs are generated Work Patterns Changes in work shift from day to evening to night Extended or excessive work hours May affect worker alertness and affect safety compliance 108 36
Non-Beam Hazards Waste Disposal Laser and Laser Waste Disposal Give or donate assure that laser complies with product safety standards provide adequate safety instructions for operation and maintenance ensure laser will be used by users trained in laser safety Return to manufacturer for credit if applicable Render inoperable (remove all means for activation) if to be disposed Dispose by contacting the LSO 109 Laser Waste Disposal-Continued Laser disposal can have landfill restrictions Hazardous materials may be found inside the laser Contaminated material must be handled in conformance with appropriate federal, provincial and local guidelines Contact the LSO for assistance 110 Medical Examinations & Surveillance Baseline eye examinations are provided by EHS Periodic eye examinations - not required In case of accidental exposure, follow McGill accident/incident/occupational diseases protocol Medical examination preferably done within 48 hours For 400 1400 nm lasers, exams must be done by an ophthalmologist 111 37
Emergency Procedures & Accident Reporting Consider wavelength, emission specs and exposure situation to assure an appropriate medical referral In the retinal hazard region, examinations should be performed by an ophthalmologist Employees with skin injuries should be seen by a physician 112 Emergency Procedures & Accident Reporting Continued If accident requires ambulance, fire and police, call 911 Then contact McGill Security Services to direct emergency vehicles to the proper location: Downtown campus: 514-398-3000 Macdonald campus: 514-398-7777 For hazardous materials spills call McGill Security Services. Hazmat response team maybe dispatched. 113 Emergency Procedures & Accident Reporting The Method Used Reporting laser accidents/incidents All accidents, incidents (near accidents) and operating irregularities must be reported to the Departmental Safety Committee and EHS for investigation, analysis and remedial action The McGill Accident, Incident, Occupational Disease Report Form must be completed and sent to EHS 114 38
The End Questions & Answers Quiz 115 39