Laser Safety Training Dr Katy Voisey Faculty of

Laser Safety Training Dr Katy Voisey Faculty of

Laser Safety Training Dr Katy Voisey Faculty of Engineering University Of Nottingham Management of health and safety is based on principles of risk assessment: Hazard the potential of a process, material, device etc. to do harm. The hazard is often quantified with regard to the severity of the damage/harm that could occur in a worst-case situation. Risk the likelihood that the potential harm would be realized in practice. The aim is to develop a safe system of work that

minimises risk. This general approach to health and safety is no different for lasers. Based on published guidance, the University has adopted administrative procedures to ensure that risks associated with laser work are minimised. Details of these administrative procedures are at http://www.nottingham.ac.uk/safety/laserindex.htm However, it should be remembered that lasers are being used in lots of different ways across the campuses and there is no one size fits all approach to laser safety local risk assessment is essential. Laser Classification

The hazard presented by a particular laser is reflected in its class. It is a legal requirement for suppliers to classify the lasers they sell. Classes 1(1M) 2(2M) 3R (formerly 3A) 3B 4 (in increasing order of ability to do harm) However, some older systems may not have appropriate labels. The class can be worked out using the yellow book and knowing the wavelength, power and pulse width (if pulsed) of the laser. http://www.aurpo.org/images/documents/ guideance/aurpogn7.pdf Laser Classification Safety of Laser Products Part 14: A users guide, PD IEC/TR 6082514

Laser Classification Class 1: Safe very low power or enclosed system Class 2: Low power (<= 1mW) visible lasers protection afforded by natural aversion (blink response) Class 3R: Medium power (<= 5mW) visible lasers as class 2, but intrabeam viewing via optical instruments may damage sight. Class 3B: Hazard from direct beam viewing and specular reflections. Class 4: Hazard from direct beam viewing and viewing of specular and diffuse reflections. Hazard to skin and fire hazard.

Whos who in laser safety: University safety officer University laser safety adviser School/Dept. laser safety officer Laser lab/project supervisor Laser workers

Breakdown of Responsibilities University Safety Office

To keep a register of all lasers. To carry out periodic checks on designated laser areas in departments and the records kept.. To provide DLSOs with adequate support in their roles. To provide yearly a training course for all new laser users DLSO To register new users To provide users with the CVCP Yellow Book/AURPO Guidelines To carry out yearly audits of designated laser areas To follow up on any problem areas identified in the audits To give advice on appropriate training for users where requested by either the user or a supervisor Breakdown of Responsibilities

Supervisors To write a protocol for work to be carried out in any area where Class 3R, Class 3b and Class 4 lasers are used. To provide adequate personal safety equipment for users To act promptly on the advice of the DLSO following an audit (Undergraduates only) To provide a copy of the Approved Scheme of Work for a project (Postgraduate/post doctoral only) To have ensured that the Project Supervisory Requirements Form has been updated and carried entries of risk assessments associated with the use of lasers.

Breakdown of Responsibilities - Users To complete the medical eye survey form if required.

To view the laser safety video To read and have a working knowledge of the CVCP yellow book/AURPO Guidelines and to know the location of the laboratory copy To understand access restrictions in designated laser areas and the operation of any laboratory door interlocks To know the location and capabilities of laser safety equipment To be aware of the MPE figures for the system(s) being used (Undergraduates only) To have read, signed, and approved a copy of an Approved Scheme of Work written by the supervisor for the project (Postgraduate/post doctoral only) To have ensured that the Project Supervisory Requirements Form has been updated and carried entries of risk assessments associated with the use of lasers. Laser User Registration

Academic supervisor to inform user to Register as a laser user User completes registration form, supervisor signs and copies User completer medical eye survey form if using 3B/ 4 lasers and sends to OH SLS* authorises form and maintains A record of users for the School OH sends letter confirming safe to work with lasers to SLS & user

User must be provided With suitable training (- university intro course - School course - Laser system training) Training recorded (PRSF, course registers) Laser User may commence laser work With suitable supervision. (I f Student, PSRF reviewed until user is competent) * SLS - School Laser Supervisor #OH - Occupational Health

laser film Notes on Practical Laser Safety The general safety precautions fall under very simple headings. a) Use of a remote interlock connector b) Key control c) Beam stop or attenuator d) Warning signs e) Beam paths f) Specular reflections g) Eye protection Laser Eyewear Eyewear is the most common and certainly the most

important aspect of personal laser protection, wherever there is some risk of laser exposure above the specified MPEs. Protective eyewear does not, however, preclude a full safety evaluation and consideration of all alternative means of affording protections - such as total enclosure of the beam, interlocks, beam dumps etc. Laser safety glasses are the last line of defence and not a convenient alternative to avoiding any engineering controls that it may be possible to implement. Procedure for Selection of Eye Protection Step 1: Determine wavelength of laser (l) Determine maximum exposure duration (t)

anticipated for the use of eye protection unintentional, accidental exposure to a visible beam where the maximum exposure may be of the order of 0.25 sec (aversion response). unintentional, accidental viewing of near IR laser beams for up to 10 sec. situations where occasional viewing of diffuse visible reflections for up to 600 sec is anticipated. 4 to 8 hour occupational viewing of a diffuse reflection (generally from an invisible beam). Procedure for Selection of Eye Protection Step 2: Determine Maximum Permissible Exposure (MPE) for desired laser

Determine MPE from l, maximum exposure duration (t), and viewing conditions determined in Step 1. MPE will be in units of [J/cm2] for pulsed lasers and [W/cm2] for CW lasers. Procedure for Selection of Eye Protection Procedure for Selection of Eye Protection Step 3: Determine the desired optical density REMEMBER: MPE was determined in Step 2! Calculate Optical Density for a CW laser:

Dl = Optical Density for CW laser = log10(H/MPE) Calculate Optical Density for a pulsed laser: Dl = Optical Density for pulsed laser = log10(E/MPE) Procedure for Selection of Eye Protection Step 4: Choose laser eye protection that meets the Optical Density requirements for the laser Compare the calculated requirements with manufacturer's specifications and find eyewear with an optical density value equal to or greater than the calculated value. Additional factors in choosing laser eyewear

side-shield protection peripheral vision requirement need for prescription glasses comfort and fit degradation of absorbing media (photo bleaching) strength of materials anti-fog

impact requirements Limitations of Eye Protection General In general, eye protection will afford adequate protection against medium power, Class 3 lasers but will seldom provide sufficient protection against direct beam viewing of CW lasers exceeding 10 W in power or pulsed lasers exceeding 10 to 100 J in output energy. Obviously, for the higher power lasers, if a plastic frame or lens bursts into flames the wearer is going to move out of the beam path very rapidly. In these situations, the laser user should attempt to eliminate the need for eye protection when using such high power lasers by using engineering controls. Multiple Wavelengths One pair of laser eyewear may not provide adequate protection from all multiple or tunable wavelengths produced by the laser. The laser user must

be very conscious of which type of eye protection is appropriate for each different wavelength which may be used in the operation of the laser. It is the responsibility of the laser equipment supervisor to assure that the appropriate eyewear (for each wavelength) is provided for all users of the laser. Summary of Laser Administration Process Laser Registrations New laser to be put into use (or change of status for existing laser) Principle investigator (laser "owner") to register laser on university form ( all 3R & above) Registration form sent to SLS* and Safety Offi

ce SLS to authorise & Ensure laser survey & risk assessment completed Safety Offi ce maintain inventory of lasers and check laser installation if necessary Laser may be put into use annual laser survey list of users risk assessment

written protocol Annual update of laser inventory confirmed with School Annual inspection by Safety Offi ce (since 2003/ 4) Change of laser or taking laser out of use: School to notify Safety Offi ce via registration form * SLS School Laser Supervisor Laser hazards in context Compare with looking directly at the sun: Solar radiation flux density at the surface of the earth ~ 1 kW/m2.

If you stare at the sun (dont do this), the pupil would contract to about 1 mm2. Therefore 1 mW of sunlight would enter the eye. For flux density at retina, use geometrical optics o o=7x108m r1= 1.5x1011m r2= 2.5x10-2m r1 r2 i i = (r2/r1)o 200 m

Laser hazards in context Compare with looking directly at the sun: Solar radiation flux density at the surface of the earth ~ 1 kW/m2. If you stare at the sun (dont do this), the pupil would contract to about 1 mm2. Therefore 1 mW of sunlight would enter the eye. For flux density at retina, use geometrical optics o r1 i = (r2/r1)o 200 m r2 i

Therefore at retina we have ~ 25 kW/m2. Now consider a weak laser, 1 mW laser pointer with 1 mm2 beam. Again 1 mW of light enters the eye. However, unlike the sun, laser light is highly spatially coherent (as if from a point source) and so is focussed to the theoretical minimum spot size d ~ f, where f is the focal length ( about 2 cm) and the beam angular divergence, typically 1 mrad. This gives d = 20 m or 2.5 MW/m2 at the retina. 100 times stronger than staring at the sun!

Recently Viewed Presentations

  • Instrumental Analysis - Louisiana Tech University

    Instrumental Analysis - Louisiana Tech University

    Sample Standard Deviation (s) B. Statistics 6. Sample Variance - s2 Instrumental Analysis Elementary Statistics I. Significant Figures • The digits in a measured quantity that are known exactly plus one uncertain digit. ... (Relative Error) Good Precision Good Accuracy...
  • Bible Timeline CASKET C reation A braham S

    Bible Timeline CASKET C reation A braham S

    Paul consistently reasoned Jesus Christ using Law and Prophets. Act 28:23 So when they had appointed him a day, many came to him at his lodging, to whom he explained and solemnly testified of the kingdom of God, persuading them...
  • Kap 5 Lover og forskrifter - iktipraksis.iktsenteret.no

    Kap 5 Lover og forskrifter - iktipraksis.iktsenteret.no

    Murerfaget Fliser i storformat Du skal få kjennskap til fliser av storformat og hva det betyr for deg som utøver av murerfaget. Du skal få kunnskap utførelsen ved montering av fliser av storformat og hva som kreves i forhold til...
  • SOC 8311 Basic Social Statistics

    SOC 8311 Basic Social Statistics

    ORGANIZATIONAL EVOLUTION Roots in Biological Evolution Theory Charles Darwin & Alfred Wallace Explanation of continuously emerging novel biological forms or attributes through population interactions with environments
  • D&C PT Contractors Role & Responsibilities Chris M.

    D&C PT Contractors Role & Responsibilities Chris M.

    Austress Freyssinet Pty Ltd Other titles: Arial Wingdings Presentation1 D&C PT Contractor's Role & Responsibilities Introduction Why do PT contractors get involved in the design of the project to start with ? What are the common efficiencies introduced to the...
  • High Performance HVAC Installation WELCOME, THANK YOU FOR

    High Performance HVAC Installation WELCOME, THANK YOU FOR

    Equipment Sizing. Refrigerant Charge. Design Target . All systems should be sealed below 25 cfm25. It's not uncommon for tests of performance systems to be at 9 to 25 cfm25. For HPHI CFM leakage = AC Ton x 400 x...
  • Food Safety Regulation - Hamline University School of Law

    Food Safety Regulation - Hamline University School of Law

    All records relating to recalled product production, HACCP plans, SSOPs, and other standard requirements must be made available for FSIS review and copy . ... Buyers or sellers of wholesale or jobbing quantities. Can include retailers who sell direct to...
  • Cax2002 - UDC

    Cax2002 - UDC

    La antigüedad: años 60 Ivan Sutherland, estudiante del MIT, realiza su tesis doctoral en la aplicación de los gráficos por computador al diseño en la ingeniería: el proyecto se llamó Sketchpad, y se considera el inicio de la industria del...