Code of Practice for Laser Safety

Transcription

1 Code of Practice for Laser Safety Policy Statement Most types of lasers operating in the visible and near infrared regions are sufficiently intense as to represent a hazard to the eye. Although damage may be caused to all parts of the eyes, the most vulnerable part is the retina, on which the beam may be focussed by the eye lens resulting in the destruction of tissues and the creation of permanent blind spots. High power lasers can also damage the skin. It is the policy of the Campus that all work involving lasers is carried out in such a way as to prevent undue risk either to those carrying out the work or to those who may otherwise be affected by the work. The Campus will seek to ensure that all relevant statutory requirements are complied with. In particular, work with lasers will only be carried out after assessment of the hazards associated with it and providing that suitable facilities, local procedures and organisational arrangements are in place. Work may only be carried out by trained competent workers and will be adequately supervised. The arrangements described below form a part of the University s Health and Safety Policy. The purpose of this document and those linked to it, is to provide practical information on how to ensure that the hazards arising from the use of lasers are properly assessed, suitable action is taken to reduce risks and safe systems of work are implemented, and adequate safety information is provided to all laser users. 1 General Exposure Measures Safety measures usually concentrate on making the beam path inaccessible, thus preventing exposure. In many applications (i.e. particle sizing, interferometry and Raman spectrometry) the laser will be enclosed. Where research applications with unenclosed high power beams are involved, a mixture of engineering controls, administrative procedures and personal protection will be needed. Lasers should be operated with as high a background level of illumination as possible to ensure that the pupil of the eye is small and in some cases it may be advisable to wear protective goggles. The goggles to be worn should be appropriate to the wavelength of the laser beam being used. Care should be taken to check the paths of all possible reflections and if necessary non-flammable opaque screens should be used to protect personnel. It is important to establish whether the laser used produces a beam in the visible part of the EM spectrum or not. In the case of the latter, personnel may be unaware that they have been exposed to laser radiation unless clear warning is given that the laser is operating. 2 General Administration Summary The key administrative elements: Faculty where lasers are used should appoint a Faculty Laser Supervisor Each Faculty should have a list of all non-office equipment lasers and laser users Each Faculty must maintain a record of users of Class 3A/3R and above lasers Each Faculty must register lasers of Class 3A/3R and above on the University Form and send a copy to the Campus EHS team A laser survey form must be completed for each laser system of Class 3A/3R and above prior to first use and on an annual basis thereafter Page 1 of 10

2 Prior to use for the first time of any laser of Class 3A/3R and above, a risk assessment must be completed and written procedures for use produced Risk assessments and laser survey forms for Class 3B and 4 lasers must be forwarded to the Campus EHS team with the laser registration form prior to first use No Class 3B or 4 laser system should be put into use for the first time with out the approval of the Faculty Laser Supervisor, and if necessary, the Campus EHS team. 3 Laser Classification Laser hazard is identified by classification of the laser (1 to 4, with 3 and 4 posing greater hazard). It is the responsibility of the laser manufacturer to provide the correct classification of a laser product. This classification is made on the basis of a combination of output power(s) and wavelength(s) of the accessible laser radiation over the full range of capability during operation at any time after manufacture which results in its allocation to the highest appropriate class. 3.1 Maximum Permissible Exposure Levels (MPE) Maximum Permissible Exposure limits are those levels of laser radiation to which, in normal circumstances, persons may be exposed without suffering adverse effects. A guide to MPE levels are given in BS EN The national MPE levels are given in GB Chapter13. They are based upon biological data collected to date. 3.2 Laser Classes Lasers are grouped according to ability to do harm, the higher the number the greater the harm. The current laser classes in UK campus are: 1, 1M, 2, 2M, 3R, 3B and 4 a) Class 1 The most limiting MPE values cannot be exceeded and no specific safety controls are required. For CW (Continuous Wave) visible lasers, the maximum limit is 70 microwatts. Class 1 operation cannot be claimed for a product containing an embedded laser of a higher class unless full-interlocked high-integrity enclosures using fail-safe interlocks are incorporated. Class 1M is a large diameter or widely divergent beam ( nm). b) Class 2 Visible lasers only, for which the MPE cannot be exceeded in less than 0.25 seconds. For CW (Continuous Wave) laser the limit is 1 mw. Class 2M is a large diameter or widely divergent beam. c) Class 3R (Previously Class 3A) Please note: wherever the Code of Practice refers to Class 3R, the same applies to the previous classification of 3A nm Lower risk than 3B, but direct viewing of beam potentially hazardous Visible lasers up to five times the Class 2 limits and invisible lasers up to five times the Class 1 limits, for which specific H (Jm-2) or E (Wm-2) values are not exceeded. d) Class 3B Page 2 of 10

3 Visible and invisible lasers not exceeding specified limits, which are 0.5W for CW (Continuous Wave) lasers and 105 Jm-2 for pulsed lasers (less for ultraviolet wavelengths). Direct beam viewing not safe to the eye, specularly reflected beams may also be harmful to the eye, diffusely reflected beam usually safe to the eye, assumed to be safe to the skin. e) Class 4 Those that exceed the limits of Class 3B Viewing a direct beam or a reflected beam is always harmful to the eye and skin, diffusely reflected beams should be assumed harmful to the eye or skin unless proven otherwise, both scattered and reflected beams can present a fire hazard. The national laser classes are: 1, 2, 3A, 3B and 4 a) Class 1 It is safe in the reasonable working condition, and no specific safety controls are required. b) Class 2 Wavelength range from 400nm to 700nm, visible lasers c) Class 3A Lower risk than 3B, but direct viewing of beam usually safe d) Class 3B Intrabeam viewing not safe to the eye, diffusely reflected beam usually safe to the eye, assumed to be safe to the skin. e) Class 4 Those that generate the hazardous diffusely reflected beam, which may be harmful to the eye or skin, and can present a fire hazard. 4 Definitions 4.1 Definition of a Laser System A laser system is a system containing one or more lasers associated with a single application or process and under the control of a single operator, i.e. lasers that are exchanged on the same system or are running simultaneously on the same experiment (e.g. pump laser and main laser). There is more than one laser system if the lasers are not operating together or are used by different operators although mounted in the same area. Laser is defined in GB as an electromagnetic radiation device undergoing excitation and then generates or amplifies the wavelength between 180nm -1mm. 4.2 Definition of a Designated Laser Area A Designated Laser Area (DLA) is an area or room where one or more Class 3B and/or Class 4 lasers are in use. Signage is mandatory at the entrance to the area/room. Page 3 of 10

4 5 Specific Organisational Arrangements The Campus EHS team develops monitors and reviews laser safety policy. Competent advice is provided by UK Safety Office. The Campus Health and Safety Committee receive recommendations from the Campus EHS team concerning the development of laser safety policy and consider reports of accidents or incidents involving lasers. Responsibility for the safety of each laser system lies with the Academic Supervisor or Principle Investigator directing the work. Each Faculty where laser systems are in use must appoint a Faculty Laser Supervisor who has sufficient authority to co-ordinate and advice upon compliance with this Code of Practice. Each laser user must ensure they comply with the Code of Practice and local procedures. The Campus EHS team will monitor the Campus's overall compliance with the Code by liaising with Laser Supervisors and carrying periodic inspections. The above objectives will be discharged as follows: 5.1 Campus EHS team 1. To provide up to date guidelines in the form of a Code of Practice for Faculty to follow 2. To keep a register of all Class 3 and 4 laser systems 3. To consult with UK Safety Office and submit the up to date registration list 4. To carry out periodic audits of designated laser areas and the records kept in Faculty 5. To provide Faculty Laser Supervisors with adequate support in their roles 6. To provide introductory training on safe use of lasers for new laser users 5.2 Faculty Laser Supervisor (See further detail regarding the roles and typical duties in the University s effective safety management document.) 1. To coordinate the registration of new laser users and new lasers of Class 3A/3R and above and to keep a record together with forwarding the information to the Campus EHS team for central record-keeping 2. To ensure the relevant University guidelines and local procedures and AURPO are brought to the attention of laser users 3. To carry out yearly audits of designated laser areas (Laser Survey Form) and to follow up on any actions and recommendations 4. To give advice on appropriate training for users where requested by either the user or a supervisor 5. To give advice on the drawing up of risk assessments and written procedures 5.3 Academic Supervisor/Principle Investigators 1. To register new lasers and users with the Faculty Laser Supervisor and to notify any subsequent significant changes 2. To carry out risk assessments and oversee the provision of written procedures for work to be carried out in any area where Class 3A/3R, Class 3B and Class 4 lasers are used 3. To ensure that the arrangements to control the hazards are implemented and followed 4. To provide adequate personal safety equipment for users Page 4 of 10

5 5. To act promptly on the advice of the Faculty Laser Supervisor following an audit of the DLA 6. (Undergraduates only) To draw up an 'Approved Scheme of Work for a project involving laser work 7. (Postgraduate/post-doctoral only) To have ensured that the Project Supervisory Requirements Form has been updated and carries entries of risk assessments associated with the use of lasers 5.4 Individual Laser Users All laser users must be aware of the class of laser they are to work with, the associated hazards and relevant precautions. The list below should be followed as appropriate and is mandatory for users of Class 3A/3R and above lasers. 1. To view the laser safety film (for Class 3B and 4 users particularly) 2. To read and have a working knowledge of the AURPO and to know the location of the laboratory copy if applicable 3. To have read and understood the risk assessment and written procedures for working with the relevant lasers. 4. To understand access restrictions in designated laser areas and the operation of any laboratory door interlocks 5. To know the location and capabilities of laser safety equipment 6. To be aware of the MPE figures for the system(s) being used 7. (Undergraduates only) To have read, signed, and approved a copy of an Approved Scheme of Work written by the supervisor for the project 8. (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. 6 Administrative Arrangements No work with the more hazardous classes of laser (Class 3A/3R, 3B and 4) may be carried out unless those laser systems and the users of them are registered within the Faculty where they are based and the laser systems registered with the Campus EHS team, see details on the registration process below. The Faculty Laser Supervisor should maintain the records for the Faculty. The Campus EHS team will maintain records of laser systems for the Campus as a whole and will request an annual update from each Faculty Laser Supervisor. 7 Registration of Lasers Each Faculty must maintain a list of lasers and users. The Campus EHS team maintains an inventory of Class 3A/3R, 3B and 4 lasers. The Principal Investigator (or other equivalent person responsible for the laser) must notify the Faculty Laser Supervisor of all new lasers prior to them being put into use for the first time. Lasers at Class 3A/3R, 3B and 4 must be registered using the laser registration form, which should be accompanied by a risk assessment and Laser Survey Form. The Faculty Laser Supervisor should forward the registration forms to the Campus EHS team and include the risk assessment and laser survey form for Class 3B and 4 lasers. Work with Class 3B and 4 lasers may not start until the Faculty Laser Supervisor has confirmed, with reference to the Campus EHS team if felt necessary, that the safety arrangements are satisfactory. The registration form is for notifying the acquisition, change of use, or cessation of use of lasers. Registration forms must be sent to the Faculty Laser Supervisor who will then forward a copy to the Campus EHS team, if appropriate (i.e. Class 3A/3R or above registrations). Page 5 of 10

6 Registration of Class 1 and 2 lasers and lasers contained within office equipment, e.g. laser printers, CD Rom drives and laser pointers (if Class 2) is not necessary. However, records should be kept by the Faculty of all other lasers. For Class 1 and 2 lasers this should be a list of lasers and their location. It is not necessary to send this information to the Campus EHS team. 8 Registration of Laser Users All users of Class 3A/3R and above lasers are required to complete a LASER USER REGISTRATION FORM before they begin work with lasers. The forms must be submitted and kept by the Faculty Laser Supervisor. For laser classes 1 and 2 in non-office type equipment, it is sufficient for the Faculty to maintain a list of users local to the laser itself, e.g. a list of names on the wall adjacent to the equipment. This can then be copied to the Faculty Laser Supervisor on a regular basis. 8.1 Requirements for NEW Laser Users The Laser User Registration Form includes a checklist to ensure that the user has obtained full information on the risks involved in their work and the procedures adopted to control them. All registered laser users should receive the following information: 1. A copy of the Campus Code of Practice 2. Any Faculty laser policy documents 3. The written risk assessments and procedures relevant to the laser systems they will be working with 4. The MPE calculations relevant to the laser systems they will be working with 5. The relevant training All registered laser users (particularly those using Class 3A/3R and above lasers) should receive appropriate training in the safe use of lasers. This should include attendance at the Introductory Laser Safety Talk provided centrally by the Campus. It must also include locally- provided training specific to the laser systems the user will be working with. Particularly for Class 3B and Class 4 laser systems there is a specific training film from the National Physical Laboratories, this is shown at the Introductory Laser Talk. For the users of the lower class lasers (1 and 2), it is acceptable to have local training specific to the experiment being undertaken as long as the hazard and risk are explained. All training should be recorded. IT IS AT THIS POINT THAT A NEW LASER USER MAY BEGIN WORK WITH THE LASER SYSTEM THEY HAVE BEEN TRAINED IN. If a laser user does not feel able to sign the registration document then they must approach the Faculty Laser Supervisor for further clarification and must not undertake any work in a designated area until they have done so. If the research worker arrives after the start of the academic year, they must arrange to view the Laser Safety Training Film and, as above, sign a statement indicating that they have understood the video and the documentation given to them. If at any time a research worker feels that they have not understood the relevant safety procedures and the general recommendations outlined, or that they are unsure about these recommendations as they relate to the designated laser area / laser system they Page 6 of 10

7 work are to work with, they should approach their supervisor who will discuss with the Faculty Laser Supervisor what further training is appropriate for the situation. 8.2 Summary of Paperwork that must be forwarded to Campus EHS team Laser registration form for lasers of Class 3A/3R and above Initial laser survey form for Class 3B and 4 lasers Initial risk assessment for Class 3B and 4 lasers 9 Medical Assessment Medical Assessment applies to all prospective users of Class 3B or 4 lasers. A medical examination is arranged by approved Occupational Health hospital. 9 Monitoring the Code of Practice - Laser Surveys 9.1 Faculty Audit The Faculty Laser Supervisor should carry out an audit of all laser systems completing a Laser Survey Form for each system of Class 3R (3A) and above. This audit should be carried out annually or sooner if there are significant changes to the laser set-up. A copy of the most recent audit should be given to the relevant academic supervisor / principle investigator and be displayed near to the laser system it refers to. Heads of Faculty should be advised by the Faculty Laser Supervisor of any problems that the audits reveal and it is the responsibility of the appropriate academic supervisor to address any such problems. The Faculty Laser Supervisor has the authority to recommend to the Head of Faculty that use of a certain facility should cease until remedial action has been taken. The Faculty Laser Supervisor will carry out a further audit on any DLA or laser system where problems have been identified no later than one month after the date of the original audit - and should the problems still exist the Faculty Laser Supervisor will again advise the Head of Faculty, who may choose to close that area to further research work until action has been taken. In the event that the survey identifies a serious risk to health and safety, the Faculty Laser Supervisor will recommend that work with the system be suspended immediately and notify the Campus EHS team. 9.2 Audit of New System Any new laser system purchased by Faculty must be registered with the Faculty Laser Supervisor prior to being put into use. The Faculty Laser Supervisor will carry out an audit on the laser system, using a Laser Survey Form, before it is put into use and copy the forms for Class 3B and 4 systems to the Campus EHS team. 9.3 University/Campus Audit The Campus EHS team aims to carry out annual audit in Faculty that uses lasers, to ensure that the guidelines for safe working are being followed. The UK Safety Office can support the EHS team by providing additional specialist or competent advice. The audit will normally cover a selection of Faculty s laser systems and a report will be sent to the Faculty Laser Supervisor and Head of Faculty. Recommendations for remedial action may be made and will be addressed through the Head of Faculty if necessary. Page 7 of 10

8 10 Precautions in Use The legislation give advice on the precautions recommended for each class of laser (see table below). As a laser user, however, the general safety precautions fall into a number of sections. The headings listed below, should be considered in relation to the system being used and its hazard classification. The aim is to reduce to a minimum the risk of exposure to hazardous levels of laser radiation and other associated hazards. 1. Use of a remote interlock connector 2. Key control 3. Beam stop or attenuator 4. Warning signs 5. Beam paths 6. Specular reflections 7. Eye protection Summary of Use Precautions Classification Class 1 Class 2 Class 3A/R Class 3B Class 4 Remote interlock Not required Connect with the room, window and door Designated laser area Not required Control of open beams, interlock connected to room or door circuits where appropriate Key Control Not required Remove key when not in use Beam Attenuator Not required When in use prevents inadvertent exposure Emission indicator Not required Indicates laser is energised device Warning signs Not required Follow precautions on warning signs Beam path Not required Terminate beam at end of useful length. Keep open beams above/below eye level Specular reflection No requirements Prevent unintentional reflections Eye protection No requirements Required if engineering and administrative procedures not practicable and MPE exceeded Protective clothing No requirements Sometimes required Specific requirements Training No requirements Required for all operator and maintenance personnel 11 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. Page 8 of 10

9 Laser safety eyewear incorporates optical filters to reduce the laser radiation to below the level of the MPE, whilst at the same time maintaining a reasonable level of visible light transmission. The filter damage threshold must be sufficiently high to withstand the maximum possible exposure long enough for appropriate avoiding action to be taken. The absorbance of the filters must be appropriate to the wavelength of the laser(s) used. Clear information must be available to identify the eyewear that is suitable for each laser and whether it is for alignment work or full protection. There are standards for laser eye protection, BS EN 207 (for full protection 180 nm to 1 mm) and BS EN 208 (for alignment work 400 nm 700 nm), GJB (national standard). Eye protection should conform to these standards and should be clearly marked to indicate the protection that is provided. Users are responsible for exercising care in the use and storage of eye protection. These items are expensive and easily scratched, degrading performance and comfort. Any defects must be notified to the user's supervisor and work requiring the defective item should cease until a safe replacement is made. 12 Risk Assessments and Written Procedures The Management of Health and Safety at Work Regulations require a risk assessment of all work activities. This applies to the use of all classes of laser but particular attention is required in the case of Class 3 and 4 lasers due to the level of hazard. The risk assessment should identify the key hazards and the precautions required to minimise the risk of those hazards causing harm. The risk assessment must be recorded in an approved format. The complexity of the risk assessment should be relevant to the class of laser, i.e. for Class 1 and 2 lasers, the risk assessment will be far simpler than for a Class 3B or 4 laser. As a result of the risk assessment, a written safe operating procedure should be drawn up for each laser system. In designated laser areas where more than one laser system may be in use, the procedures should be expanded to cover the precautions in place for the whole area. Written procedures should be displayed locally and all laser users of the systems are expected to be aware of them and to follow their recommendations. Links to examples of written procedures: For Use of Class 3B and 4 laser systems For Use of Multi-user Laboratories For Undergraduate Projects 13 Other Hazards In carrying out a risk assessment for work with lasers, there are other hazards that may need to be considered, the main ones being: 1. Electrical - high voltages 2. Chemical/Fume - sample preparations, use of dyes and solvents (apply COSHH Regulations) 3. Mechanical - manual handling, trips, slips, noise, vibration 4. Optical - open beam paths, misalignment problems, mounting of optics 5. Fire - high power, direct and reflected beams 6. X-rays/electromagnetic interference As with all hazards, the risk must be assessed and suitable precautions to minimise the risk, identified and implemented. Page 9 of 10

10 14 Maximum Permitted Exposure Levels (M.P.E.L.) Calculation It is useful to carry out the calculation for each laser system in order to show the factor by which the MPE is exceeded. All laser users should then be made aware of the results to emphasise the hazard associated with the laser system they are using. The MPEL values are dependent upon: 1. the wavelength of the radiation 2. the exposure time or pulse duration 3. the spectrum of wavelengths, when the tissue is exposed to more than one wavelength 4. the nature of the tissue exposed 5. the angular subtense of the source (which determines the size of the retinal image) in the wavelength range from 400 nm to 1400 nm. Example of MPE calculations are introduced in GB Chapter13 and Appendix A. You can also find the examples from MPE Level Heading. 15 Summaries of Relevant Standards British Standard BS EN , Safety of laser products - Part 1: Equipment classification, requirements and user s guide BS EN and IEC 825-2, entitled "Safety of optical fibre communication systems" AURPO's GUIDANCE ON THE SAFE USE OF LASERS IN EDUCATION AND RESEARCH, 2007 University Code of Practice for Laser Safety GB Safety of laser products - Part 1: Equipment classification, requirements and user s guide GBZ Occupational Exposure Limit for Hazardous Agents in the Workplace Page 10 of 10