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Laser safety Introduction

Laser safety Introduction. B. Fischer. T-ray group meeting 08/06/06. but:. Regular training is required by law Initial laser training for new staff Gives you the opportunity to become aware again of some issue Possibility to reflect on your practice.

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Laser safety Introduction

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  1. Laser safety Introduction B. Fischer T-ray group meeting 08/06/06 Laser safety

  2. but: • Regular training is required by law • Initial laser training for new staff • Gives you the opportunity to become aware again of some issue • Possibility to reflect on your practice finally: You have only two eyes ! Motivation • It might appear unnecessary • Our lab is safer than most other T-ray lab in the world source: http://www.adrenotex.de/augenklappe.htm

  3. navigators had to stare into the sun if using a sextant In older times Why do pirates wear patches? intense light damages your eyes! sources: http://en.wikipedia.org/; http://www.stuckiag.ch/shop/de-ch/dept_380.html

  4. Eye damage – 400-1400 nm Visible and near-infrared light enters the eye and is focused tightly on the retina (10-25 mm diam). even in VIS, only about 5% will be absorbed in visual pigments retinal burn: (irreparable) damage cw and long-pulse lasers: mainly thermal, 400-600 nm also photochemical

  5. Eye damage – 315-390 nm Light penetrates to the lens and can cause damage here (photochemical cataract)

  6. Eye damage – 180-315nm and >1400nm light stopped by the cornea photokeratitis, corneal burns (similar to sunburns) (1.5 mm – 2.6 mm light penetrates in aqueous humour, large volume, rather eye-safe)

  7. Laser safety – other hazards • Skin exposure • Particularly high power and/or UV lasers • Fire hazard • Beams hitting flammable materials • Electrical shocks • Gas discharge lasers can operate with high voltage (kV) and high currents (50-100 A) • Chemical hazards • Toxic laser materials • Dyes and solvents • Chemical lasers there is a general understanding that accidents of this kind greatly outnumber eye strikes

  8. Laser safety legislation • Legal Responsibilities – for employer & employee • Occupational Health & Safety at Work Act • Work Equipment Regulations • Management Regulations – risk assessments

  9. Australian Standards

  10. European Health & Safety Law • Health & Safety at Work Act • The act places duties on both employers and employees • It is criminal law and can be enforced against criminals and organisations • The act can be summed up as; • Employers duty: ‘To safeguard so far as reasonably practicable the health, safety and welfare of employees and others affected by the work’. • Employees duty: ‘To take reasonable care for the safety of themselves and others; to cooperate; not to be reckless’

  11. Typical Work Equipment Regulations • All equipment must be suitable • Maintained in an efficient state • Maintenance recorded • Restricted to trained users • Users must have information and training • Access prevented to dangerous parts • Adequate controls and lock-offs • Suitable environment

  12. European standards on laser safety • deals with lasers and laser products, i.e.product or assembly of components which contain lasers or laser systems • E.g. compact disc players • includes also light emitting diodes (LEDs) (modern LEDs are high-power, highly directional light sources) • indicates safe working level for laser radiation • classification of lasers & laser products according to degree of hazard • labeling  warnings • minimize accessible radiation, control measures • protection against non-radiation hazards associated with lasers

  13. Reasoning behind classification • Classification of laser determined by: • Accessible Emission Limit (AEL) • Maximum level of laser radiation accessible over its full range of capability during operation at any time after its manufacture  • To classify a laser, you need to know: • Laser wavelength • Exposure duration • Viewing conditions • Each laser class has a set of safety control measures that manufacturers and users must obey •  Manufacturers should supply this classification (attention: slight differences between USA and Europe -> Australia?)

  14. Laser classification Class 1 Safe under reasonably foreseeable operation Class 1M Generally safe – some precautions may be required Class 2 Visible light at low power, blink limits risk Class 2M Visible light at low power, generally safe – some precautions may be required Class 3R “Low” risk for direct viewing of beam Class 3B Viewing beam hazardous, diffuse reflections safe Class 4 Hazardous under all conditions, eyes and skin

  15. Class 1 (safe) • Safe under reasonably foreseeable conditions of operation, including the use of optical instruments for intra-beam viewing • rather complex calculation, but rule of thumb for cw lasersVIS (400-700): 0.39 mWNIR/IR (700-1400): slowly increasing, e.g. 1.6 mW for 1 mmMIR (1.4–4 m) 10 mW (“eye-safe” communication)FIR (> 4 m) 1000 W/m2 • measurement area: normally iris with diameter 7 mm • A product may contain high power laser with higherclassification, if effective engineering controls restrict routine exposure to Class 1 AEL • CD, laser printers • possibly machining, etc. • in lab: cleverly set up spectrometer (?)

  16. Class 1M • New class, mainly for EN60825-2 regulations to deal with fibres (communications) & LEDs • Wavelength range  302.5 nm to 4 m • Generally these lasers are as “safe” as Class 1 • Except for diverging or large area beams when collecting optics used  These large beams may be focused to a spot of sufficient intensity to cause damage to the retina

  17. Class 2 (low power) • Max output – 1 mW • Visible only: 400 nm to 700 nm • Blink response of eye affords protection (0.25 s) • E.g: • Supermarket scanner • many HeNe laser, some laser diodes • legal laser pointers • note: recent research questions reliability of blink reflexconsider also fatigue, alcohol, drugs, ... • Class 2M divergent or broad-aperture sources, which meet Class 2 standard without additional optics • OK if collecting optics not used

  18. Class 3R (low to medium power) • Direct intrabeam viewing is hazardous, but risk is lower than for 3B • wavelength > 302 nm • maximum AEL 400-700 nm = 5 times AEL of class 2, i.e. 5 mW • maximum AEL at other l = 5 times AEL of class 1 • E.g: • Surveying equipment • many laser pointers • Some HeNe and laser diodes in teaching & research labs • there is no class 3A anymore

  19. Class 3B (medium power) • Max output- 0.5W (500 mW) • Includes all visible and non-visible lasers • Direct intrabeam viewing is always hazardous • Viewing diffuse reflections is normally safe provided: • Eye is not closer than 13 cm from diffusing surface • Exposure duration is less than 10 seconds • e.g. • many laser diodes • small solid-state lasers • small ion lasers

  20. Class 4 (high power) • > 500 mW • capable of producing hazardous diffuse reflections • capable of producing also skinburns and fire hazards • e.g. • most solid-state lasers • laser diode bars, some single emitters • most ion lasers

  21. (Repetitively) Pulsed lasers • exposure from any single pulse shall not exceed AEL for single pulse AEL depends on pulse duration, wavelength, ... • average power of a pulse train of duration T shall not exceed the AEL for a single pulse of duration T • for wavelength larger than 400 nm (thermal limits): average pulse energy shall not exceed single pulse AEL times correction factor AE train = AELsingle N–0.25 N number of pulses (by the way, there are more details to it)

  22. Consequences • appointment of laser protection officer (invisible class 3R, 3B, 4) • labelling • training (class 1M, 2M, 3R, 3B, 4) • protective enclosures where applicable, access restrictions • interlocks (class 3B and 4)

  23. Labelling • Labels for laser user & laser servicer • Correct labels should be provided by manufacturer • If size or design of laser makes labeling impractical (e.g. laserdiode), put it on the mount or base.(only in rarest circumstances labels should be included only with user information orplaced on package) • Laser starburst warning label on all laser products of Class 2 and above • Access panels, Safety interlocked panels Should be labeled if access to laser radiation in excess of the AEL for Class 1/1M is possible on their removal or over-riding source: http://www.lasermet.com/labels/labels-updated.html

  24. Labelling II • every laser needs a label with warning level increasing with class • e.g. class 2 • e.g. class 3R • lasers of class 3R, 3B, 4 need labelling of aperture • if radiation is outside the 400-700 nm range, “laser radiation” needs to be replaced by “invisible laser radiation” or “visible and invisible laser radiation” source: http://www.lasermet.com/labels/labels-updated.html

  25. MaiTai -> Class 4 laser

  26. Laser safety – University policy • Appointed Laser Safety Officer (LSO) • All lasers (3R, 3B, 4) must be registered(?) • All lasers and users conform to Australian Regulations • Risk assessment & safe method of work completed at workplace • All laser users must attend risk assessment & safe method of work briefing • The supervisor (Bernd or Tamath) overseeing the laser project must ensure safe working practices as followed

  27. Practical laser safety • There is a hierarchy of controls to ensure the safe use of lasers: • Risk Assessment and Safe Method of Work • (1) Engineering controls • (2) Administrative controls • (3) Personal protective equipment (PPE)

  28. Engineering controls • To Restrict exposure to laser radiation use:  • Housings  Put the laser in a box if applicable • Enclosures  Use tubing on (long) laser runs • Beam stops  Block beams as soon as is possible • Interlocks  Prevent unauthorised access to danger • Warning lights  Informs others of the possible danger Advantage: improves stability and reduces contamination Disavantage: Not applicable in laminar flow conditions • remote sensing  align beams without danger

  29. but also: Never bodge and no temporary fixes It compromises safety Engineering controls II Controls should not be over restrictive and hamper ease of working

  30. Administrative controls • But:Engineering controls may not provide adequate protection in cases such as:  • Phases of research when laser system is being commissioned • Servicing of laser equipment • Manufacture or research into laser design • Laser alignment • Special projects: waveguides, near-field, dynamis • In these situations: Use Administrative controls to minimise risk so essentially in many, but not all situations we are working in

  31. T-ray labs around the world

  32. It’s also about communication Clear instructions? Clearly understood?! Actually, your colleagues in the lab are often more at risk, if you do something dodgy, than you are, because they do not know that you are going to do it.

  33. Examples for administrative controls • Warning Signs & NoticesProminently displayed – clear and unambiguous • Labels at entrances to lab or workshop containing Class 3B or 4 laser Laser Controlled Area (Class 3B or 4 laser) • Restricted to authorized persons • By physical means: walls & doors, Locks or number pads • Key Control • Class 3B & 4 laser keys removed when not in use • Kept secure in key cabinet to which authorized users only have access • Training • Only trained persons allowed to use 1M, 2M, 3R and the more 3B and 4 lasers Maintenance & Service Manuals • Must be available and easily accessible to laser users

  34. Personal protective equipment (PPE) • Used only when: • Risk of injury or harm can not be suitably minimised by engineering controls etc • Laser safety goggles • required for Class 3R outside of 400-700 nm window, 3Band4 • saves us in teaching labs, if everything else is ok, i.e. direct beam viewing is not possible due to engineering controls • Fire resistant clothing, gloves, overalls • against hazards associated with lasers (noise, chemical etc) • Protective clothing when exposure to radiation exceeding maximum permissible exposure for skin (MPE), i.e. possibly strong class 4 lasers • use during • alignment or open beam experiments • maintenance and servicing Employers are obliged to provide employees with PPE!

  35. VIS, 400 – 700 nm, attenuation to < 1 mW Goggles • Purpose: to reduce level of incident laser radiation upon cornea to below MPE maximum permissible exposure, essentially: make it a class 1 laser! • Filter: Sufficient optical density (OD) to attenuate incident radiation to MPE rule of thumb 0.4 mW – some mWs, but check your wavelength and conditions(OD of 5 means that a filter transmits less than a part in 105 at that wavelength) • Legal requirement to comply with: • Personal Protective Equipment Product Directive (89/686/EEC)July 1995 • European Standards; • EN207:1998 Filters & equipment used for personal eye protection against laserradiation  • EN208: 1999 Personal eye-protectors used for adjustment work on lasers and laser systems

  36. scale number corresponds to optical density Markings on goggles In order to meet legal requirements, the goggles need to be marked with • Wavelength or wavelength range in nm against which protection is afforded • Scale No or lowest scale No if protection against a spectral range is afforded • The manufacturers identification mark • Test mark of the inspection body (CE or possibly DIN for rather old goggles) Marking with OD alone is NOT sufficient ! The scale number confirms that the filter withstands at least 10 s and that also the frame does not disintegrate

  37. Frames of goggles high safety (TOPS) possibly weak points at side ok balance between optimal safety and acceptance by the user (what happens with prescription glasses?) sources: Lasermet, Laservison

  38. wrong brand? Practical laser safety again If you do not find at least eight safety flaws in here contact me (discreetly)

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