08/06/2006 Laser safety1 Laser safety Introduction B. Fischer T-ray group meeting 08/06/06

2 Motivation  It might appear unnecessary  Our lab is safer than most other T-ray lab in the world 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 ! source:

3 In older times Why do pirates wear patches? sources: navigators had to stare into the sun if using a sextant intense light damages your eyes!

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

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

6 Eye damage – nm and >1400nm photokeratitis, corneal burns (similar to sunburns) light stopped by the cornea (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 ( 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  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  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)

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 1Safe under reasonably foreseeable operation Class 1MGenerally safe – some precautions may be required Class 2 Visible light at low power, blink limits risk Class 2MVisible light at low power, generally safe – some precautions may be required Class 3R“Low” risk for direct viewing of beam Class 3BViewing 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 lasers VIS ( ): 0.39 mW NIR/IR ( ): slowly increasing, e.g. 1.6 mW for 1  m MIR (1.4 – 4  m) 10 mW ( “ eye-safe ” communication) FIR (> 4  m) 1000 W/m 2  measurement area: normally iris with diameter 7 mm  A product may contain high power laser with higher classification, 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 EN regulations to deal with fibres (communications) & LEDs  Wavelength range  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 reflex consider also fatigue, alcohol, drugs,...  Class 2Mdivergent 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 nm = 5 times AEL of class 2, i.e. 5 mW  maximum AEL at other = 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 skin burns 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 = AEL single 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. laser diode), put it on the mount or base. (only in rarest circumstances labels should be included only with user information or placed 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:

24 Labelling II source:  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 nm range, “laser radiation” needs to be replaced by “invisible laser radiation” or “visible and invisible laser radiation”

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  remote sensing  align beams without danger Advantage: improves stability and reduces contamination Disavantage: Not applicable in laminar flow conditions

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

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 & Notices Prominently 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)  Laser safety goggles required for Class 3R outside of nm window, 3B and 4 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 Used only when:  Risk of injury or harm can not be suitably minimised by engineering controls etc Employers are obliged to provide employees with PPE!

35 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 10 5 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 laser radiation  EN208: 1999 Personal eye-protectors used for adjustment work on lasers and laser systems VIS, 400 – 700 nm, attenuation to < 1 mW

36 Markings on goggles  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) In order to meet legal requirements, the goggles need to be marked with scale number corresponds to optical density 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 sources: Lasermet, Laservison balance between optimal safety and acceptance by the user (what happens with prescription glasses?) high safety (TOPS) possibly weak points at side ok

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