COB Laser Safety Training

Transcription

1 COB Laser Safety Training Department of Occupational and Environmental Safety Out of the Blue The Israel Festival 1998 by Yoram Goldhammer

2 COB Laser Training Topics Covered Are: Laser Definition and History The Electromagnetic Spectrum Optical Portions for the EMS Beam Characteristics and Design Basic Laser Operation Laser Exposure Limits and Terms Laser Hazard Classifications Laser Biological Effects UV Action Spectra for Cataracts Blue Light Retinal Injury Laser Safety Control Measures Administrative Safety Practices Good Laser Safety Work Practices Common Causes of Laser Accidents Non-Beam Safety Hazards The Aversion Response Medical Eye Surveillance OSHA Laser Regulatory Reference Site

3 LASER definition - AN ANACRONYM For LIGHT AMPLIFICATION BY THE STIMULATED EMMISSION OF RADIATION - predicted by Einstein in 1916 A term coined by Gordon Gould in 1957 based on Towne s MASER 1957 Laser Inventor and patent holder for the LASER. (most of his laser patents are now expired) Theodore Maiman built first ruby laser in 1960

4 Laser History Einstein predicts existence of stimulated photon emission Charles Townes and Arthur Schawlow invents MASER using ammonia gas and microwave radiation. The technology is very close to a Laser, but does not use a visible light. Townes granted Maser patent in 1959 and with Schawlow is awarded first optical maser patent in He won the Nobel Prize in Gordon Gould designs first optical laser in His 1959 patent was wrongfully refused. In 1977 Gordon Gould wins patent war to receive, what would have been, the first laser patent Theodore Maiman made the first ruby laser- considered to be the first successful optical or light laser. Many historians claim that Theodore Maiman invented the first optical laser, however, Gordon Gould won the patent The first gas laser (helium- neon) was invented by Ali Javan Kumar Patel invents first CO2 laser.

5 The Electromagnetic Spectrum The Big Bang! The Mysterious Universe 1930 by Sir James Jeans Talullah Bankhead She read the book 1927, the Belgian priest Georges Lemaître proposed the universe began with the explosion of a primeval Atom. In a 1950 radio talk show, astrophysicist Fred Hoyle coined the expression,"the Big Bang

6 Laser Wavelengths Laser Type Wavelength (nm) Region ArF Gas Excimer 193 UV-C Kr-Cl 222 Krypton BBO SHG XeCl Gas Excimer 308 Cataracts! UV-B N2 Gas 337 UV-A XeF Gas Excimer 351 Ar Gas Ion 364 N2T Gas 428 Visible NeCd Gas Ion 422 Ar Gas Ion DPSS Semconductor 532 Cu Metal Vapor HeNe Gas InGaAlP Semiconductor Krypton Gas Ion Ruby Solid State Visible Ti-Sap IR NdYLF Solid State 1053 NdGlass 1060 NdYAG 1064 Most injuries Invisible Nd-YAP 1080 Ar Gas 1090 HeNe Gas 1152 Far IR Only visible region colors are shown

7 Lasers - Basic Characteristics Laser light is different: - Monochromatic - Directional (Collimated) - Coherent - Intense (brightest known light source) - Polarized Laser light is more hazardous: - Focuses a lot of energy onto a tiny area - Can damage skin or eye cornea or retina - Can initiate explosions w/toxic plumes - Can change the chemistry in the cells/tissue

8 Beams are Directional emergent diameter Laser Beam Divergence (milliradians) Emergent beam diameter (mm)

9 Laser Diffuse Target Laser Flat Specular Target Laser Curved Specular Target

10 Laser Eye Damage Wavelengths Corneal Hazards nm Inflammation conjunctivitis cataracts 300nm Lens Hazard nm Photochemical Cataracts300nm Photokeratitis and erythema Retinal Hazards nm color/night vision degradation retinal burns Corneal Hazards 1400 nm - 1mm milky cornea Corneal burns Thermal cataracts 760-3k nm Ultraviolet Visible Near Infrared Mid/ Far Infrared B, C* A Actinic nm A Colors are for visible only B, C Blue light hazard UV symptoms are delayed Ar H-Ne R G N Argon He-Neon Ruby Gallium CO2 ND:YAG invisible (1064 nm) Thermal damage dominates with pulsed lasers at any visible wavelength

11 Lasers - Basic Design mirror Laser Pump laser medium Laser Optical Cavity translucent mirror Lens The optical cavity contains the media to be excited and mirrors to redirect the laser photons back along the same general path. The pumping system uses photons from another source such as a xenon gas flash tube (optical pumping) to transfer energy to the media, electrical discharge within the pure gas or gas mixture media (collision pumping), or relies upon the binding energy released in chemical reactions to raise the media to the metastable or lasing state. The laser medium can be a solid (state), gas, dye (in liquid), or semiconductor. Lasers are commonly designated by the type of lasing material employed.

12 Lasers -Basic Operation

13 Imbedded vs Enclosed Lasers Imbedded Laser: a laser inside another piece of equipment with the lower class laser label shown outside. Enclosed Laser: a laser inside another piece of equipment with the same class laser label shown outside. EXTRA PRECAUTIONS ARE REQUIRED WHEN INSIDE THE HOUSING OF IMBEDDED LASERS!

14 An Imbedded Class 4 Laser note warning labels

15 Laser Exposure Limits - Terms MPE or Maximum Permissible Exposure: The highest laser energy to which the eye or skin can be exposed without hazardous or adverse biological effects MPE depends on wavelength, exposure time and target organ (eye or skin): high MPE implies low hazard NHZ or Nominal Hazard Zone: Area within which the MPE is equaled or exceeded Must be delineated for Class 3b and 4 Lasers NOHD or Nominal Ocular Hazard Distance: The point reached from the laser source down its unobstructed beam axis beyond which there is acceptable eye exposure

16 MPE IS USED FOR: LASER CLASSIFICATIONS Based on Accessible Emission Limit (AEL) AEL= MPE x area of limiting beam aperture OPTICAL DENSITY DETERMINATIONS OD specifies attenuation provided or required OD= log 10 (E/MPE) or log 10 (H/MPE)

17 Nominal Hazard Zone E=MPE NHZ NOHD NOHD r = distance E = irradiance (exposure) T = exposure time or duration Laser Safety Eyewear must at worn at all times in the NHZ

18 Ultraviolet (UV) MPE s Maximum Permissible Exposure UV Region Wavelength MPE UV-A nm 1mW/cm2 8 hrs UV-B nm 500 uw/cm2 1 min UV-C nm 100 uw/cm2 1 min Normal light DO YOU SEE WHAT EYE SEE? Same in UV light

19 Basic Laser Hazard Classifications: Class 1 : Safe if not disassembled Class 2 : An eye hazard if you stare into beam the aversion response class Class 3A: Eye hazard if collated or focused into eye using telescope/binoculars Class 3B: Instantaneous eye hazard if the direct beam or its reflection is viewed Class 4: Instantaneous eye hazard if direct, reflected, diffuse beam or specular reflections are viewed Possible skin and fire hazard

20 Laser Biological Effects - Damage Laser beam damage can be from: - thermal (heat) - acoustic waves - photochemical reactions (cell chemistry disrupters) Primary sites of damage: - eyes (cornea, lens, pupil/iris, retina) - skin (dermis, epidermis)

21 Laser Related Distinctions LASER MODE OF USE - Continuous Wave (CW) vs. Pulsed vs. Repetitive Pulsed REFLECTIONS - Specular mirror vs. diffuse random reflections MECHANISM OF INTERACTION - Thermal vs. Photochemical vs. Acoustic VIEWING TIME - Aversion Response Time (0.25 second) vs Prolonged viewing time CORONEO EFFECT - oblique UV rays hitting lens stem cells vs direct rays

22 Laser Biological Effects - Eye Sensitivity Retina: Visible, IR-A Lens: UV-A Cornea: UV-B, UV-C, IR-B, IR-C Retina Ocular Hazard Region is Visible nm plus near Infrared IRA nm

23 Laser Biological Effects - Vision Receptors The eye has three types of vision receptors: Rods in retina areas surrounding the cones: for night vision and shades Cones in the macula-fovea portion of the retina, imbedded near where the optic nerve emerges:.. for color vision Novel photo receptors (retinaldehyde pigmentation), non-rod/non-cone: for blue light ( nm) circadian rhythm regulation of serotonin.

24 Laser Optical Media Effects Beam Diffusion (spreading of the beam) Wavelength Absorption ( by water vapor, smoke) Concentration of laser beam by Retina: The eye can concentrate a laser beam by x100,000 Retina temperatures at the point of focus may reach 1000 degrees F (depending on laser) Wavelengths above 1300 nm (far infrared) are absorbed by and damages the cornea and lens, not the retina. Visible and near infrared may cause retinal damage

25 Laser Biological Effects - The Eye Lens Lens - UV-A The crystalline lens absorbs almost all incident energy to wavelengths of nearly 400 nm. In youth, a very small amount of UV-A reaches the retina, but the lens becomes more absorbing with age. Our intraocular filters effectively filter different parts of the UV spectrum and allow only 1% or less to actually reach the retina. Nevertheless, this small fraction of energy--if phototoxic-- could still be of concern. Finally, oblique rays entering the eye from the temporal side, can actually reach the equatorial (germinative) area of the lens. Adapted from Sliney, USACHPPM

26 Laser Biological Effects - The Retina Exposure to a Q-Switched invisible Nd:YAG Laser (1064nm) may go undetected. Retina has no pain sensory nerves. Visual disorientation may not be apparent until considerable damage has occurred.

27 Laser Eye Damage Wavelengths UV-C: nm UV-B: nm UV-A: nm Light and the Eye UV- C absorbed by air UV-B hits Cornea Visible and IR-A hits Macula and Retina UV-A hits lens Far Infrared hits cornea UV Action Spectrum - Ultraviolet cataractogensis peaks at 300 nm (UV-B) for photochemical injury mechanism

28 Photochemical Blue Light Retinal Injury For intense UV near nm Blue Light Staring at welding Arc or Sun Delayed appearance (24-48) hrs Staring at Blue Light Lamps Photochemical, blue light eclipse retinal injury from lengthy (greater than 10s) and intense nm light exposure

29 R E L A T I V E I N T E N S I T Y SPECTRAL RESPONSE OF EYE If the beam is equal to or g.t. the pupil diameter, the difference in power entering the eye between bright and dark adapted eyes will be g.t. 30X. Wavelength (nm) shift: night vs daylight photopic daylight vision scotopic nigh vision 525nm 570 nm. Human eye perception of brightness is strongly dependent on wavelength. You cant rely on human eye as a light meter..

30 Laser Safety Controls: PPE PERSONAL PROTECTIVE EQUIPMENT: Wear proper protective eyewear with correct optical density, and side protection with curved lens to reduce specular reflections Wear heat protective gloves when needed Wear appropriate lab protective clothing as required for the chemicals and heat effects you may encounter Wear insulating high voltage safety shoes when necessary PPE: BE SPECIFIC AND CORRECT

31 PPE: Protective Eyewear PPE: WEAR THEM ALWAYS WHEN INSIDE THE NHZ! INSPECT FOR CRACKS.

32 3 Types of Laser Protective Eyewear Neutral density: Cut-Off: Bandpass: absorbs and reflects visible wavelengths transmits light at one end of spectrum, but not the other transmits light in a narrow range of wavelengths Select eyewear to meet ANSI Table 5 requirements, marked with the correct wavelength/optical Density, has side shields and doesn t exceed power density recommendations.

33 Engineering Control Measures Beam housings/barriers/curtains Shutters, over-the-top solid beam blockers Attenuators Remote firing and viewing controls Interlocks and automatic cutoff switches The Real First Line of Defense INSPECT AND ENSURE ALL ENGINEERING CONTROLS ARE OPERATIVE

34 Engineering Controls-Classes 1 and 2 All Classes Considered Only for Indoor Use Class 1 less than 0.4 uw Protective housing installed Enclosed Class 3b or 4, housing interlocks MPE exceeded, have laser controlled area Class uw to less than 1 mw Protective housing installed Conspicuous warning labels Area laser warning sign posted MPE exceeded, use viewing portals or display screens to preclude Enclosed Class 3b or 4, housing or service access interlocks or same with tool removal

35 Engineering Controls - Class 3a Class 3a 1 to 5 mw Protective housing installed Conspicuous Equipment Warning labels Interlocks for removable housing parts Permanent beam stop or attenuator provided Appropriate area warning signs Interlocked/tool accessed service panel MPE exceeded, laser control area devised portal viewing/display screens. A pulsed 3a laser requires a Danger sign

36 Engineering Controls - Class 3b Class 3b. 5 to 500 mw Same as Class 3a plus the following: Beam not entirely enclosed establish: NHZ Determinations begins here Controlled area and Implement control measures NHZ leaves indoor Controlled area: Controlled area have limited beam path Should have key controlled switch Have remote interlock connector Permanently attached beam stop Alarm, warning light or verbal countdown Limited Open Beam Path: NHZ Determination Warning signs posted Controlled area with only trained authorized personnel

37 Engineering Controls - Class 4 Class 4 greater than 500 mw Same as Class 3b plus the following: Equipped to allow remote shut off or beam reduction to below MPE Entry safety controls in place Have remote monitoring and firing

38 Administrative Control Measures Standard operating procedures SOPs Training Warning Sign/ labels Laser Registration

39 Good Laser Safety Work Practices Use appropriate safety protective eyewear with corner protection and correct filter. Reduce laser output to the lowest possible power. Close down the shutter and increase attenuation. Use beam trap at terminal end of laser. During alignment use diffuse screens, remote viewing systems and invisible beam detection fluorescent cards. Keep beam path well below eye level and mount a solid stray beam shield above the laser beam. Remove unnecessary objects away from laser. KEEP YOUR BODY PARTS OUT OF BEAM PATH!

40 Common Causes of Laser Accidents Unsafe Practices: Please Note: 60% of incidents occur during alignment procedures and most go unreported during the critical first hours post exposure. Inappropriate eyewear Altering the beam path (adding optical components without regard to beam path) Bypassing interlocks during alignment Accidental firing of laser or turning on electricity Improper handling of high voltage Igniting a laser goggle strap with a laser beam DO NOT BREAK THE CHAIN OF SAFE PRACTICES

41 Non-beam Chemical Hazards Organic dyes are the major chemical hazards Toxic, mutagenic, carcinogenic, or highly reactive plumes Laser gases, interactive target gases and coolants, compressed gases USE STANDARD LABORATORY TECHNIQUES TO PREVENT INJURY: PPE, PROPER CHEMICAL STORAGE, FUME HOODS

42 Aversion Response This is the established First Line of Defense and refers to the turning of the head or movement of the eyes away from the source of laser light within the first 0.25 second of an occurrence or an incident and includes the blink reflex time. This response may not occur in all incidents. The 0.25 sec response time is used in laser hazard calculations. It works well in the IR region when the heat is felt on the face. CAUTION: NEVER RELY ON THIS REFLEX RESPONSE FOR TOTAL EYE PROTECTION

43 Medical Eye Surveillance Eye screening is suggested for Class 3b/4 laser workers when a retinal dysfunction is present. When injured or if an injury is suspected, do contact a doctor immediately, do not hesitate. For laser eye injuries, the first 24 to 48 hours following injury is the most critical for treatment. Secure laser accident scenes as soon as possible after an accident to facilitate an accurate assessment of the causes. DO NOT HESITATE IF INJURED, SEEK PROMPT MEDICAL HELP, NOTIFY SUPERVISOR, SECURE THE ACCIDENT SITE!

44 Medical Eye Surveillance Indicators and Symptoms of Laser Eye Injury A pop is felt or a flash is seen with an after-image(s) in the complimentary color of the laser Disturbance in reading vision Temporary flash blindness or loss of vision A new blind spot is noticed (scotoma) Difficulty seeing blue or green colors secondary to cone damage with pigmentation of the retina NOTIFY AT X, YOUR SUPERVISOR AND SEEK MEDICAL ATTENTION IMMEDIATELY. PRESERVE THE ACCIDENT SCENE FORINVESTIGATION BY THE LSO. Laser safety officer

45 Medical Eye Surveillance Indicators and Symptoms of Laser Eye Injury Cont. Exposure to the invisible carbon dioxide laser beam (10,600 nm) can be detected by a burning pain at the site of exposure on the cornea or sclera. 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). When the retina is affected, there may be difficulty in detecting blue or green colors secondary to cone damage, and pigmentation of the retina may be detected. Exposure to the Q-switched Nd:YAG laser beam (1064 nm) is especially hazardous and may initially go undetected because the beam is invisible and the retina lacks pain sensory nerves. 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.

46 Laser Hazards Information Readily available on the Internet Contact Campus Safety at x This instructor at T30