The radiation safety of lasers used for display purposes

Transcription

1 The radiatio safety of lasers used for display purposes This is a free-to-dowload, web-friedly versio of HSG95 (First editio, published 1996). This versio has bee adapted for olie use from HSE s curret prited versio. ISBN Price This guidace booklet describes the desig, istallatio ad operatioal requiremets for the radiatio safety of display laser istallatios. It is relevat to supplier ad user alike ad icludes the use of lasers for theatrical, broadcastig, advertisig/promotioal ad exhibitio purposes. HSE Books Page 1 of 34

2 Crow copyright 1996 First published 1996 ISBN All rights reserved. No part of this publicatio may be reproduced, stored i a retrieval system, or trasmitted i ay form or by ay meas (electroic, mechaical, photocopyig, recordig or otherwise) without the prior writte permissio of the copyright ower. Applicatios for reproductio should be made i writig to: The Office of Public Sector Iformatio, Iformatio Policy Team, Kew, Richmod, Surrey TW9 4DU or [email protected] This guidace is issued by the Health ad Safety. Followig the guidace is ot compulsory ad you are free to take other actio. But if you do follow the guidace you will ormally be doig eough to comply with the law. Health ad safety ispectors seek to secure compliace with the law ad may refer to this guidace as illustratig good practice. Page 2 of 34

3 Cotets Itroductio 1 Regulatory bodies 2 Chapter 1 Laser hazards 3 Chapter 2 Supplier requiremets 5 Basic safeguards 5 Moutig of equipmet 5 Display area demarcatio ad restrictio of access 5 Supervisio 6 Settig up 7 Sitig ad security of laser cotrols 8 Emergecy laser radiatio cut-off 8 Determiatio of exposure coditios 8 Had-over arragemets 9 Veue cosideratios 9 Idoor displays 9 Ope air displays 10 Chapter 3 User requiremets 12 Had-over arragemets 12 Supervisio 12 Laser safety officer (LSO) appoitmet 12 Operator ad LSO traiig 12 Istallatio modificatio by the user 13 Chapter 4 Istallatio safety assessmet 14 Itroductio 14 Hazards 14 Emissio reflectio 14 Emissio scaig 15 Veues 16 What the assessmet should deal with 16 Emissio evaluatio 19 Statically projected CW ad pulsed emissios 19 Scaed emissios 20 Simultaeous exposures 21 Appedix A Defiitios 23 Appedix B Types of display laser 29 Appedix C MPE data 29 Appedix D Cotacts 32 Page 3 of 34

4 Refereces 33 Further iformatio 34 Page 4 of 34

5 Itroductio 1 This guidace provides employers ad employees who use lasers (see Appedix A for defiitios) i etertaimet, theatre ad public exhibitio work ad compaies that maufacture or supply such equipmet with comprehesive iformatio o the radiatio safety problems they eed to cosider. 2 If you are a maufacturer, desiger, importer, supplier or istaller of display laser equipmet or of compoets for such equipmet, you have a duty uder the Health ad Safety at Work etc Act 1974 (1) to cosider the safety of your products whe they are used by a perso at work. 3 If you are a employer who uses display laser equipmet either at your ow premises or uder cotract to a veue operator, you have duties uder the Health ad Safety at Work etc Act 1974, the Maagemet of Health ad Safety at Work Regulatios 1992 (2) ad the Provisio ad Use of Work Equipmet Regulatios 1992 (3). You must: (a) assess the health ad safety risks caused by your work activity, icludig: (i) (ii) risks to employees ad members of the public, for example members of a audiece who may be exposed to hazardous laser radiatio; ad take measures to cotrol these risks so far as is reasoably practicable. (b) esure that the work equipmet you provide is suitable, i ay respect which it is reasoably foreseeable will affect the health ad safety of ay perso (3). The curret British Stadard (6) o the safety of laser products gives useful iformatio o safe equipmet desig ad lists the laser radiatio persoal exposure limits that are used by HSE (see Appedix C). 4 If you are a veue ower who lets cotracts for laser shows to be provided at your premises, you have a duty uder the Maagemet of Health ad Safety at Work Regulatios 1992 to co-operate with the istaller so that they ca complete the laser show safely. It is good practice for you to satisfy yourself that the istaller has adequately assessed the safety of the laser show at your premises ad, i particular, has addressed the matters dealt with i this guidace. 5 Chapters 2 ad 4 should be read by maufacturers, suppliers ad desigers of display laser istallatios (see Appedix A for defiitio). Much of the advice i these chapters will also be relevat to cotract hire compaies ad to compaies uder cotract to provide permaet bespoke display laser istallatios at cliet premises. 6 Chapter 3 should be read by permaet display laser istallatio users such as ightclub ad theatre owers ad by hire compaies that operate display laser istallatios at cliet premises. Users should also read Chapter 4 so that they are aware of the safety assurace issues affectig display laser istallatios. 7 Display purposes icludes the use of a laser for theatrical, broadcastig, advertisig/promotioal or exhibitio purposes. 8 The terms laser product ad laser system are defied i the curret British Stadard. These defiitios iclude light emittig diodes (LEDs) because there are circumstaces i which some desigs ca be hazardous. As a geeral rule, The radiatio safety of lasers used for display purposes Page 5 of 34

6 exposure limits for LED devices (see Appedix C, especially Note to Table 6) that are ot also true lasers *, are more relaxed because their agular subtese is greater tha that for lasers; they therefore do ot produce retial images as small as those produced by lasers. Noetheless, to the extet that some LED devices could be hazardous i display applicatios, this guidace applies to their use. 9 This guidace does ot deal with hazards such as fire, explosio or electrical safety. If you eed iformatio o these safety matters, you should read the Guide to health, safety ad welfare at pop cocerts ad similar evets (7). 10 The geeral priciples of protectio described i this guidace apply without prejudice to ay code of practice dealig with a particular display laser applicatio, provided that it specifies a comparable stadard of safety. Regulatory bodies 11 The relevat eforcig authority depeds o the premises at which a display laser istallatio is operated (5) ad is either the local authority or the Health ad Safety (HSE). 12 May places of public etertaimet, icludig discos ad ightclubs, require a etertaimets licece from the local authority. May local authorities expect display laser istallatios to be operated i compliace with this guidace before they issue such liceces. 13 I the case of outdoor displays, other regulatory bodies may eed to be cosulted. These iclude the maritime ad harbour authorities, the Police ad the Civil Aviatio Authority (CAA). See Appedix D. * Devices that emit radiatio primarily by stimulated emissio withi a optical resoator. The radiatio safety of lasers used for display purposes Page 6 of 34

7 Chapter 1 Laser hazards 14 Most lasers that are used i etertaimet, theatre ad public exhibitio work have outputs high eough to cause a sigificat risk of eye ijury. If the laser output power is greater tha 0.5 watts, ski bur may also be a sigificat risk. Figure 1 Direct laser viewig 15 The eye is particularly at risk because of the way i which it focuses the special light produced by lasers that emit at visible (400 to 700 m) ad ivisible, ear-ifrared (700 to 1400 m) wavelegths. 16 Lasers produce coheret light which, whe looked at, appears to the eye to have come from a very distat source. Cosequetly, the image formed o the retia by a laser source is always icredibly small ad therefore of very high power desity. 17 Retial image sizes of oly a few micros are typical which meas that power desity may be icreased by compared to that eterig the eye (see Figure 1). 18 Laser powers of just a few milli-watts ca damage the retia log before atural aversio resposes such as blikig ca take place. 19 The effect o the retia is similar to burig a piece of paper with a magifyig glass o a suy day. 20 By cotrast, a o-coheret source of radiatio, such as a light bulb, is less hazardous to view because it forms a exteded rather tha a poit image whe focused by the eye (Figure 2). Power desity at the retia is therefore lower tha that produced by a laser of equivalet radiat power. 21 Eye ijury thresholds deped upo a umber of factors such as wavelegth, exposure duratio ad viewig situatio. Ijury severity followig overexposure depeds upo the part of the retia that is overexposed ad the extet of ay bleedig withi the eye. Effects rage from partial blidess to total loss of sight i the affected eye. The radiatio safety of lasers used for display purposes Page 7 of 34

8 Figure 2 Exteded source viewig 22 Ijury to the macular* regio of the retia will cause great damage to the cetral field of view i the affected eye, makig itricate tasks such as readig almost impossible. Damage at the poit where the optic erve eters the eye may result i permaet loss of visio. I both cases, damage may be associated with bleedig withi the eye which may further impair visio. 23 Laser iduced damage to the retia is always permaet. Keypoits Display laser istallatios that use lasers with radiat powers greater tha 5 milli-watts are capable of damagig a perso s sight if viewig is ucotrolled. Istallatios that use lasers with radiat powers that exceed 500 milli-watts are capable of causig eye ijury eve whe exposure times are very short (micro-secods) ad may also be a ski bur hazard. Laser-iduced eye damage occurs because lasers of these powers ca overheat ad bur parts of the photo-sesitive layer withi the eye called the retia. Sight may be further damaged by such overexposure if the retia haemorrhages; this fills the ier chamber of the affected eye with blood, makig visio very blurred. Lasers produce light that is highly o-diverget. Their emissios may therefore be hazardous to view over very log distaces. Multi-watt display laser istallatios may be hazardous at rages up to several hudred metres. The extremely high radiatio power desities produced by most lasers that are used i display applicatios create reflectio hazards of greater overexposure risk tha those associated with covetioal light sources. Surfaces aroud the display veue which would ot ormally cause reflectio hazards uder covetioal lightig may therefore eed to be assessed for viewig safety. * Part of the retia cotaiig the highest cocetratio of coe cells ad therefore the poit at which visual acuity is at its highest. The radiatio safety of lasers used for display purposes Page 8 of 34

9 Chapter 2 Supplier requiremets Basic safeguards 24 Egieerig desig requiremets, such as robustess ad positioal stability of optical elemets withi a display istallatio, deped greatly o iteded use. Relevat factors are whether the istallatio is to be temporary or permaet, ad whether it is for idoor or outdoor use. Safeguards relevat to all istallatios are discussed i this sectio. Reflective surface Mirror Ball joit Lockig screws Figure 3 Example of a exteral optical compoet Moutig of equipmet 25 Laser systems ad all associated effects devices should be secure agaist iadvertet displacemet or misaligmet. It may also be ecessary to protect the istallatio from uauthorised cofiguratio chages. Display area demarcatio ad restrictio of access 26 Ay area where accessible emissios could lead to persoal exposures i excess of the applicable Maximum Permissible Exposure value (MPE; see Appedix A) durig ormal operatio of the istallatio ad durig maiteace ad settig up, should be idetified by the supplier ad commuicated to the user i had-over documetatio. 27 These locatios should be desigated by warig sigs as laser hazard areas, ad etry to them restricted to authorised people, who will take appropriate precautios, eg wearig eye protectio. 28 Suppliers who are ot istallers should provide iformatio about istallatio desig ad operatioal safety so that the istaller ca make the ecessary display area demarcatios. 29 Laser display modes (projected output patters) should take place withi a predetermied area. This is best achieved by maskig the effects head to cofie beam movemet. Maskig materials should be rigidly mouted ad made of either black-paited steel or alumiium plate or, where there is o fire hazard, similarly treated block board. 30 For sigle laser apertures, used to project both static ad scaed emissios, it may ot always be possible to provide fixed maskig because of the differig agular coverage requiremets for each type of emissio. I such The radiatio safety of lasers used for display purposes Page 9 of 34

10 circumstaces maskig should be desiged to be iterchageable, so that the correct maskig may be selected for each display mode. This ca be achieved by a effects head gobo (see Appedix A for defiitio), fitted with suitable maskig for each display mode. The correct maskig may the be selected automatically by the istallatio cotrol system. Supervisio 31 It is good practice for suppliers to appoit a laser safety officer (LSO) for istallatio projects they udertake for a cliet. The LSO should have executive rather tha just advisory resposibility for this work. He/she should also be ivolved i the examiatio ad audit of egieered ad admiistrative safety provisio before had-over of a ew istallatio to the user. 32 It is good practice for the LSO to be ivolved i the preparatio of had-over documetatio for the user. 33 Supervised istallatios should be desiged so that hazardous emissios are ot accessible at ay poit less tha 3 m above ad 2.5 m laterally from ay locatio at which a member of the audiece or public may gai access durig a display (see Figures 4 ad 5). For usupervised istallatios, it is good practice to icrease the vertical separatio distace to 6 m. 34 Members of the audiece should ot be able to expose either themselves or others i excess of the applicable MPE value through irresposible behaviour, eg by climbig furiture to gai a better view of performers or by placig reflective objects i beam paths. 35 It is good practice for suppliers who are also istallers to agree the ecessary supervisio with the istallatio user. These details should be icluded i had-over documetatio. Veue cross-sectioal view Figure 4 Vertical separatio distaces Veue pla view Figure 5 Lateral separatio distaces The radiatio safety of lasers used for display purposes Page 10 of 34

11 Settig up 36 Display istallatios should be set up i accordace with a safe system of work. 37 Where practicable, emissios should be reduced to below ormal operatig levels ad access to display areas should always be restricted to competet, traied persoel. 38 Display areas should be clearly demarcated by warig sigs ad, preferably, sealed off by barriers durig settig up procedures. 39 Appropriate eye protectio should be wor if there is a risk of eye ijury (4). Sitig ad security of laser cotrols 40 All display laser products of class 3B (6) ad above should be desiged to prevet uauthorised use. Emergecy laser radiatio cut-off 41 Display laser istallatios should be provided with oe or more clearly idetifiable ad easily operated emergecy stop cotrols. The frequecy of maiteace ad correct operatio checks of these cotrols should also be specified. Determiatio of exposure coditios 42 The locatios of hazardous accessible radiatio (ie those that exceed the applicable MPE value) arisig durig ormal operatio ad followig fault coditios should be idetified ad poited out to the user before istallatio commissioig ad had-over. This will require comprehesive emissio safety assessmet by either calculatio or measuremet. 43 Some of the factors to be cosidered whe idetifyig the locatios of hazardous emissios are: (a) (b) (c) the persoal exposure risks arisig from reasoably foreseeable fault coditios; the extet to which potetial target materials are specular reflectors, eg gloss-paited surfaces are more so tha matt-paited surfaces; whether, i the case of diffuse reflectors such as matt-paited surfaces, specular reflectio occurs followig illumiatio at high agles of icidece. 44 Specular behaviour should be assumed i all cases where there is ay doubt about a surface s reflective properties. 45 Calculatio accuracy should be cofirmed, wherever practicable *, by suitable measuremets of accessible emissios withi the defied laser display area. This should be doe both durig ad upo completio of equipmet istallatio. 46 Cofirmatory measuremets are particularly importat where there is a risk of hazardous exposure to scaed laser radiatio followig fault coditios, or where there is the potetial for reflectio off surfaces that have idetermiate reflective properties. * For statioary CW beams, measuremet dow to the class 3A AEL (6) is always practicable. However, HSE recogises that measuremet dow to the applicable MPE ad of scaed emissios may be impracticable. The radiatio safety of lasers used for display purposes Page 11 of 34

12 47 The radiatio emissio measuremet procedure give i the curret British Stadard applies pricipally to laser product classificatio. However, these requiremets may still be adhered to, as appropriate, for the purpose of display laser istallatio safety assessmet. Had-over arragemets 48 It is good practice for suppliers who are also istallers to prepare had-over documetatio for the user. It should specify the health ad safety precautios ad provisio ecessary for the safe operatio of the display laser istallatio. 49 The had-over documetatio should iclude: (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) calculatios ad supportig measuremets of exposure levels at defied positios withi the display area, i keepig with this guidace, or otherwise demostratig the overall safety of the istallatio; clear istructios o the use ad effect of display cotrols; details of all permissible display effects, their safety implicatios ad the costraits o their use; iformatio o maual shutdow ad surveillace requiremets; iformatio o automatic emergecy shutdow systems, their mode of operatio, maiteace requiremets ad fuctio verificatio; details of routie servicig ad maiteace procedures, their frequecy, who should carry them out, ad details of protective eyewear ad/or clothig required; details of all routie adjustmet ad aligmet checks to be carried out by the user, to iclude frequecy, record keepig ad corrective actio requiremets: exteral optical compoet checks are especially importat; operator experiece ad traiig requiremets; the supplier s address ad telephoe umber or those of its LSO; ad ay special coditios to be observed. 50 Had-over documetatio should iclude scale diagrams ad/or photographs which show the dimesios of the istallatio ad display area. It is good practice to esure that these are adequate for idepedet verificatio of emissio safety by the eforcig authority. Veue cosideratios Idoor displays 51 Mezzaie ad raised floors, balcoies ad staircases are all areas where people may be exposed to laser radiatio. Careful hazard assessmet of beam paths ad accurate laser maskig are therefore importat. 52 Suppliers who are also istallers should esure that mirrors exteral to the effects head (see Appedix A for defiitio) are securely mouted ad iaccessible to uauthorised people. Clampig mechaisms should be tamperproof ad, so far as practicable, desiged to be fail-safe. Mirrors that would shie hazardous emissios ito public areas if misaliged should be masked to restrict reflectio agles to a rage that miimises this risk. 53 The supplier should also specify i the had-over documetatio the type ad frequecy of exteral optical compoet checks to be carried out by the user. Checks for correct aligmet of all optical elemets, such as mirrors, should be carried out daily accordig to a specified procedure. The possibility of other reflectio hazards should also be icluded i the documetatio, eg hazards arisig from covetioal, suspeded lightig rigs, reflective decor (eg mirror tiles), ad wet surfaces. The radiatio safety of lasers used for display purposes Page 12 of 34

13 54 I some istallatios it may be possible to physically prevet access to emissios passig betwee display poits by moutig the laser system behid a false ceilig. Where this is doe, warig otices should be posted at appropriate positios to idicate that parts of the false ceilig should ot be removed durig laser operatio. Ope air displays 55 The security ad robustess of exteral targets is particularly importat i ope air displays because they are affected by weather, vibratios from traffic ad, sometimes, deliberate iterferece ad vadalism. Remember that at typical outdoor evet projectio distaces, eve small misaligmet of exteral optical compoets or of the laser beam itself ca result i a grossly mistargeted hazardous emissio. 56 It should ever be assumed that buildigs, roofs ad walkways etc close to or withi the display area are uoccupied; people may appear uexpectedly. 57 Care should be take to avoid reflectio hazards from objects such as lamp posts, scaffoldig, glazed areas, stretches of water, wet surfaces ad objects members of the audiece may uitetioally place i laser emissios, eg reflective balloos. If a beam is to be trasmitted from a glazed booth or through a widow of a buildig, special precautios should be take to elimiate hazardous reflectios. Wherever possible widows, through which a beam is to be projected, should be secured ope or, better still, removed. Further guidace o outdoor displays is give i Chapter 4 uder Veues. Key poits Suppliers have a key role i display laser istallatio safety assurace. They must desig ad build systems that will be safe so far as is reasoably practicable. A safe display laser istallatio has the followig features: (a) protective housigs for laser systems ad effects heads; (b) maskig aroud laser apertures to restrict errat beams should they arise; (c) robust ad rigidly mouted laser system(s) ad exteral optical compoets, so that emissio misaligmet caot occur; (d) emissios that do ot expose people above the applicable Maximum Permissible Exposure value (MPE), eve whe reasoably foreseeable faults occur; (e) emergecy safety cut-off devices that termiate a display whe problems occur; ad (f) key cotrol for tamperproof operatio. Suppliers should provide iformatio o equipmet safety checks ad maiteace procedures for users ad safety iformatio for istallers who set up their products. Suppliers who are also istallers should provide iformatio o the admiistrative safety arragemets the user eeds to make, for example: (a) laser cotrolled area demarcatio requiremets; ad (b) supervisio requiremets. Suppliers who are also istallers eed to make proper istallatio commissioig arragemets. Laser safety officers have a role i this process. The radiatio safety of lasers used for display purposes Page 13 of 34

14 Chapter 3 User requiremets Had-over arragemets 58 A istallatio should ot be brought ito service by the user util operators have bee traied i its safe operatio. 59 It is good practice for veue operators to defer takig resposibility for a istallatio util the supplier has provided had-over documetatio. This should be detailed eough to eable istallatio operators to fully uderstad the procedures ecessary for the safe operatio ad maiteace of the istallatio. 60 Oce agreed with the supplier, the coditios set out i had-over documetatio should ot be varied. Chages to the way i which a istallatio is operated should oly be made followig cosultatio with the supplier. Supervisio 61 The operatio of display laser istallatios should be supervised by authorised, traied operator(s) uless all the followig requiremets are met (see also paragraphs 31 35): (a) (b) (c) the istallatio is ot desiged to sca audieces or the public; the istallatio is permaetly istalled at the veue; ad the istallatio has bee desiged to operate etirely automatically ad is tamperproof. 62 Operators eed to be vigilat so that if there is equipmet failure, audiece uruliess or ay other usafe coditio, the display ca be stopped. Laser safety officer (LSO) appoitmet 63 Users should esure that a LSO, kowledgeable i the evaluatio ad cotrol of laser hazards ad capable of implemetig the laser safety precautios specified by the supplier, is appoited i all cases where a istallatio does ot meet the requiremets of paragraph 61. The LSO should have executive rather tha advisory resposibility for the day-to-day maagemet, operatio ad maiteace of the display istallatio. Operator ad LSO traiig 64 Operators ad LSOs should, as appropriate to the level of hazard posed by the display laser istallatio ad the resposibilities assiged to them by the user: (a) possess a detailed kowledge of the laser system(s) used by the istallatio, eg (i) (ii) (iii) (iv) (v) laser type, radiat power ad beam divergece, emissio wavelegths, effects capabilities, accessible emissio levels ad exposure hazards posed by each display mode, operatig cotrols, ad thorough kowledge of the operatio of all safety related cotrol systems; (b) complete ad log all routie daily system aligmet checks specified by the supplier; these should iclude checks for correct beam aligmet with targets, such as fixed mirrors ad mirror-balls etc, ad emergecy cut-off fuctio tests; The radiatio safety of lasers used for display purposes Page 14 of 34

15 (c) (d) (e) (f) be coversat with emergecy shutdow procedure followig equipmet failure or audiece uruliess; be aware of ay special arragemets for esurig safety, such as restrictios o areas where members of the audiece may stad; be familiar with relevat guidace material, icludig this guidace, ad have a basic uderstadig of the harmful effects of laser radiatio, its propagatio properties through air ad reflectio properties at surfaces; ad kowledge of how to carry out emissio safety assessmets (ormally oly a LSO role). Istallatio modificatio by the user 65 The user should be fully aware of the rage of adjustmets ad special effects made available by the supplier. If ay part of the equipmet is modified to produce a effect outside the supplier s specificatio, the user should esure that ay calculatios, measuremets ad further modificatios ecessary for the assurace of safety are carried out. Key poits Users eed to be competet to operate display laser istallatios. They should: (a) (b) appoit a laser safety officer ad provide effective supervisio uless the istallatio is permaet, desiged to operate etirely automatically ad does ot sca audieces; ad esure that all operators are traied to operate ad maitai their istallatio safely ad that they receive geeral istructio o laser hazards arisig from visibly emittig lasers ad the safety precautios that eed to be take. Users eed to have effective systems of work for maiteace, aligmet checks ad settig up procedures. If safety assessmet of these activities idicates that there is a risk of hazardous persoal exposure, employees must be provided with appropriate protective eyewear. Users should determie the extet of ay laser hazard areas that arise durig a display evet so that persoal access ca be cotrolled. The user should esure that the miimum separatio distaces give i this guidace are observed (see Supervisio i Chapter 2). The radiatio safety of lasers used for display purposes Page 15 of 34

16 Chapter 4 istallatio safety assessmet Itroductio 66 This chapter deals with the requiremets for the safety assessmet (see Appedix A for a defiitio) that should be udertake before a display laser istallatio is put to use. 67 The cotractual arragemets betwee suppliers, users, istallers ad veue owers are complex ad the resposibility to carry out the safety assessmet, i full or i part, may fall to ay combiatio of these parties. This chapter should therefore be read by all employers ivolved i work with display laser istallatios. 68 The safety assessmet must be appropriate to the viewig coditios that are likely to arise both durig ormal operatio of the display istallatio ad followig faults i its operatio. 69 Although it is possible to assess exposure hazards largely by calculatio, where practicable, the supplier should cofirm assessmet accuracy by suitable measuremets made at the time of commissioig a istallatio. 70 Ivisible laser emissios (ie outside the wavelegth rage 400 to 700 m) ad collateral radiatio should ever be eglected i safety assessmets. I particular, laser eergy sources, such as the gas discharge tubes used i gas lasers, may emit hazardous levels of ultraviolet radiatio ad may therefore be hazardous durig maiteace procedures. Hazards 71 Most laser systems used for display purposes exceed Class 1 or 2 criteria as defied i the curret British Stadard. May are Class 4 ad are capable of causig ski burs ad damage to the eye, especially the retia. Ay laser-iduced damage to the retia is always permaet. 72 Eye ijury thresholds deped upo a umber of factors ad ot just upo beam power desity (irradiace); exposure duratio ad viewig coditio are equally importat. 73 Class 4 lasers are capable of causig eye damage i all types of viewig coditio; that is, durig direct ocular exposure, specular reflectio ad, i some istaces, diffuse reflectio viewig coditios. 74 The very low divergece typical of the output from a display laser system meas that a statioary laser beam may remai hazardous for distaces up to several hudred metres. Emissio reflectio 75 Specular reflectios occur at smooth, shiy surfaces such as mirrors. Rough surfaces such as masory ad air cotamiats such as smoke ad dust produce diffuse reflectios ad scatter. Appedix A further defies these terms. 76 Specular reflectios ca be just as hazardous as the primary laser beam. Diffuse reflectios are much less hazardous because the surface irregularities that cause them destroy beam coherece ad cause scatter. Cosequetly, the eye is exposed to reduced power desity ad forms a exteded image o the retia that, i most exposure circumstaces, is less hazardous. The radiatio safety of lasers used for display purposes Page 16 of 34

17 Rotatioal actuator colour selectio device Dark move Emergecy Cut-off device Orthogoally mouted XY scaers Colour selectio soleoids Plae mirror Gobo Dichroic mirror Figure 6 Mai compoets of a laser effects head Emissio scaig 77 Laser emissio scaig is typically produced by a pair of galvaometermouted mirrors oscillatig at right agles to each other. Scaig device cotrol is ormally achieved by some form of programmable cotroller (PC) * although i some istallatios it is achieved maually. 78 Scaig applicatios preset a special viewig coditio whereby a cotiuous wave (CW) * emissio is perceived as a series of pulses as it passes rapidly across the eye. 79 Scaig frequecy is therefore a importat determiat of ijury threshold ad as such, requires careful evaluatio before a scaed display ca be cosidered safe to view. 80 Scaed emissios pose less risk of eye damage tha static emissios because beam movemet reduces exposure time. But hazardous exposure ca still arise if accessible emissios are ot properly evaluated, especially if fault coditios arise ad scaig patters chage uexpectedly. 81 It should ever be assumed that because a hazardous CW emissio is beig scaed at high frequecy across a display area it will be safe to view. Veues 82 Hazardous exposure to laser emissios may occur i a variety of circumstaces; by direct exposure to the beam emitted at the laser aperture itself or from beams produced by exteral optical compoets such as mirrors. The existece of uexpected reflective surfaces should also ot be overlooked. 83 Idoor displays, such as those at discos ad ightclubs, may preset a risk of uexpected laser reflectio from orametal mirrors or tiles, or from covetioal lightig rigs. * These terms are defied i Appedix A The radiatio safety of lasers used for display purposes Page 17 of 34

18 84 I outdoor displays remember that, eve whe accessible emissios are cosidered to be below the applicable MPE value, the presece of a laser emissio may still cause distractio to people uaware that a display is takig place. For example, uexpected laser emissio may dazzle or disorietate motorists ad aircraft pilots. There is also the risk of iterferece with air traffic cotrol avigatioal lights ad traffic sigals o roads ad railways. All these factors should be assessed before a outdoor display is allowed to take place. As a geeral rule, it is good practice to esure that emissios are projected at agles below the horizotal ad termiated withi the area over which the orgaiser has cotrol. If this is impractical ad the display is withi 10 miles of a airfield (either civil or military), the display orgaiser should esure that the Civil Aviatio Authority (CAA) is cotacted for advice - see Appedix D for address. What the assessmet should deal with 85 The curret British Stadard requires displays that take place i usupervised areas to comply with Class 1 or 2 criteria but, although this is good advice, the stadard does ot idicate how such compliace is to be demostrated. 86 The usefuless of classificatio criteria to idicate exposure hazards from large ad highly cofigurable display laser istallatios is limited. The accessible emissio, upo which classificatio is always based, may be so veue-specific ad alterable by the istaller or user at the time of commissioig that classificatio becomes difficult ad less relevat tha the use of MPE values. This is especially true of scaed emissios where the applicable MPE value (see Appedix A for defiitio) is the most restrictive value obtaied from three separate assessmets ( Emissio evaluatio page 19). 87 Cosequetly, display istallatio safety assessmet should always place greater emphasis upo MPE cosideratios tha o gettig the istallatio classificatio right. 88 The aim of safety assessmet is to provide assurace that emissios produced durig a display caot lead to persoal exposures above the applicable MPE value i both ormal operatio ad followig fault coditios. Table 1 summarises the criteria that apply to MPE selectio for various exposure situatios ad Figure 7 shows schematically the major questios that eed to be aswered i safety assessmet. Appedix C cotais the MPE data published i the curret British Stadard. The radiatio safety of lasers used for display purposes Page 18 of 34

19 Table 1 Applicable MPE values - Selectio Criteria Summary Spectators (ie members of the public ad/or audiece) Employees (of supplier/istaller or user) Performers (eg actors, dacers, musicias etc) Accesible emissios that arise i ormal operatio The applicable MPE should be based o cotious, direct ocular exposure to the emissio(s). Geerally as for spectators except that, where specific safety traiig is give, the applicable MPE for CW emissios may be based o the eye aversio respose time of 0.25 secods, eg durig settig up procedures. MPE relaxatios followig reasoably forseeable fault coditios The applicable MPE time base should either match the respose time of ay safety-related cotrol system, desiged to termiate emissio upo detectio of a fault, or match the time take for the emissio to be maually termiated. For faults that cause CW emissio, the applicable MPE may be based o the eye aversio respose time of 0.25 secods. As for employees but the traiig should iclude the use of stage choreography as a meas of assurig that occular exposure risk is egligible. Where a emissio, although accessible, is ot able to be viewed by the eye, the applicable MPE may be based o the appropriate ski exposure value. A example of this situatio would be where that agle of illumiatio by the laser ad the part of the performer s body beig exposed (eg the feet) make ocular exposure a practical impossibilty. NB See Appedix A for applicable MPE defiitio 89 For some display situatios it is acceptable to base the safety assessmet o the assumptio that potetially exposed people will have competet eye aversio resposes. But remember, these ca be cosciously suppressed; for example, by childre who deliberately stare ito a hazardous emissio, or by people takig prescribed medicatios ad/or alcohol. Aversio resposes should therefore ot be relied o to give protectio agaist exposure to emissios that are iteded to be viewed. They are oly likely to give adequate protectio i circumstaces where exposure is iadvertet, eg followig fault coditios, ad where exposure will be very brief. 90 Viewig aids must also be cosidered whe determiig the applicable MPE value. I most circumstaces it is best to ba their use durig a display. But if this is impracticable, the safety assessmet should assume that collectig optics up to 50 mm i diameter could be used. MPE values may therefore eed to be reduced by a factor of up to 50 compared to that for uaided viewig. Viewig aids iclude optical devices such as bioculars, but ot prescriptio spectacles. The radiatio safety of lasers used for display purposes Page 19 of 34

20 Display iteded to be viewed? (ie audiece scaig) No p Are emissios iaccessible? (eg by separatio distaces, area demarcatio, barriers, supervisio, or emissio maskig) Yes p Are emissios iaccessible durig reasoably forseeable fault coditios? (eg scaig mechaism faults) Yes p Display applicatio is safe Yes p No p Accessible emissio below applicable MPE for ormal operatio (see Table 1) p No Yes p Accessible emissio below applicable MPE for reasoably forseeable fault coditios (see Table 1) p Yes No No p p Display applicatio is usafe Figure 7 Safety assessmet decisio chart 91 The safety assessmet should meet the followig guidelies: (a) (b) (c) (d) (e) (f) Emissios iteded for viewig should be safe ad without risk to health. The applicable MPE should ot be exceeded followig persoal exposure up to the maximum time for which a emissio could remai accessible; Emissios that are ot iteded to be viewed, ie all those that are potetially hazardous, should be physically iaccessible. If this is impracticable, admiistrative cotrols may be relied o, provided that they esure that hazardous exposure will ot occur. Such cotrols iclude the demarcatio of laser hazard areas by fecig (eg rope barriers), i cojuctio with warig sigs ad ivigilatio by istallatio operators. Reasoably foreseeable istallatio fault coditios, particularly scaig failure, should ot lead to persoal exposure above the applicable MPE value (see Table 1). Sigle compoet faults such as failure of a beam scaig device, its associated power supply or ay programmable cotroller formig part of the istallatio, should always be cosidered as reasoably foreseeable. Potetially hazardous uexpected exposure situatios, eg the sudde appearace of uauthorised people at hazardous viewig locatios, or audiece uruliess, should be idetified so that everythig reasoably practicable may be doe to reduce their likelihood. With the exceptio of prescriptio leses, due accout should be take of the effect of viewig aids upo the appropriate value of the MPE i circumstaces where these are likely to be used. Evaluatio of emissios havig a diameter greater tha that of the relevat limitig aperture (7 mm for ocular MPE cosideratios) should take accout of ay variatio i itesity with positio withi the beam: the limitig aperture should always be placed where the greatest emissio occurs. The radiatio safety of lasers used for display purposes Page 20 of 34

21 92 It is good practice for the safety assessmet to be fully documeted so that it ca be checked by the user, a appoited cosultat ad, whe requested, by the relevat eforcemet authority. Emissio evaluatio 93 The accuracy of exposure hazard calculatio for a particular emissio ultimately depeds upo the accuracy ad correct use of product data supplied by the maufacturer of the istallatio, especially the maufacturer of the icorporated laser system(s). I this respect, the criteria used by laser system maufacturers to specify emissio parameters eed careful attetio. This is because they vary from maufacturer to maufacturer ad eve betwee products marketed by the same maufacturer. For example, beam divergece may be give as a half agle istead of the more commo full agle. Exposure hazard calculatios should always be based upo full agle cosideratios. Statically projected CW ad pulsed emissios 94 These emissios usually occur where a laser beam is directed at a exteral optical compoet, such as a mirror-ball. I this case the icidet emissio, ulike the reflected beam, is ofte ot iteded to be accessible ad so, provided that the advice give i this guidace about separatio distaces ad the provisio of maskig is implemeted, exposure evaluatio is ot ecessary. However, the reflected emissio will ofte be accessible ad should be assessed for viewig safety. 95 Where a emissio is iteded to be viewed or where viewig is likely because the ecessary separatio distaces caot be maitaied, persoal exposure should be costraied to the applicable MPE value. 96 For pulsed emissios, MPE determiatio is complicated by the eed to cosider ot just sigle pulse exposure situatios but also exposure to a pulse trai. I such cases the applicable MPE value is the most restrictive of three separate emissio assessmets; oe based o exposure to a sigle pulse i the pulse trai, aother based o time-averaged exposure to the pulse trai ad aother based o a empirical costrait o the sigle pulse MPE value. Criteria for these assessmets are give i the curret British Stadard; they are summarised i Appedix A uder the headig Applicable Maximum Permissible Exposure value. Scaed emissios 97 This sectio deals with miimum safety requiremets for display modes that ivolve the projectio of scaed emissios at audieces ad members of the public. 98 For displays iteded to be viewed by a audiece, demostratio of eye safety durig ormal operatio may be possible eve for a sca patter produced by a Class 4 laser system. But if scaig fails ad a emissio is brought to rest very rapidly, eg because galvaometer-mouted mirrors cease to move correctly followig mechaical, electrical or software failure, accessible emissios capable of causig eye ijury could occur well before eye aversio resposes had time to operate. 99 A Class 4 laser with oly moderate radiat power ca expose people above the applicable MPE value i less tha a microsecod. Aversio resposes that take aroud 0.25 secods to occur are therefore o protectio agaist exposure to such emissios. The radiatio safety of lasers used for display purposes Page 21 of 34

22 100 Safety related cotrol systems (SRCS), operatig o sca failure detectio, are also ulikely to tur off a high power laser i a time short eough to reder it safe to view. See Appedix A for a defiitio of SRCS. 101 Therefore, if ay reasoably foreseeable istallatio fault coditio could cause a accessible emissio i excess of the applicable MPE value (see Table 1), direct scaig of a audiece or the public should ot be permitted. 102 The priciples ad techiques used i evaluatig ad cotrollig statically projected CW ad pulsed emissio exposure hazards apply equally to scaed emissios. However, i this case the applicable MPE value has to be calculated rather tha simply looked up i the relevat table i the curret British Stadard. This requires a umber of assumptios to be made about the way i which scaed emissios appear to the eye. I particular, values for effective pulse legth (EPL) ad pulse repetitio rate (PRF) have to be chose. See Appedix A for defiitios. 103 There is also the problem of how to assess reciprocatig sca patters, ofte referred to as flat scas. These display modes have PRF ad EPL values that vary with viewig locatio withi the emissio. 104 There may also be sigificat beam dwell ad therefore a icreased EPL at the edges of sca patters because the emissio is mometarily brought to rest ad set back i the opposite directio at these locatios. Cosequetly, beam dwell or bright-ups as they are ofte called, eed careful evaluatio. It is good practice to cofigure display modes so that bright-ups are cofied to locatios outside the display area. 105 Display istallatios that are iteded to sca audieces or members of the public should have the followig features: (a) (b) (c) (d) (e) Multiple scaig compoets, so that failure of ay sigle compoet results i either o accessible emissio or oe that remais eye-safe because of the cotiued operatio of other compoets withi the system. Scaed patters geerated by separate optical compoets, movig i mutually orthogoal plaes, are a good example of this techique. If oe scaer fails, the resultig lie sca patter produced by the other scaer ca be desiged to be eye-safe. Separate power supplies for those compoets for which simultaeous power failure would produce hazardous emissio. A cotrol system that does ot produce hazardous emissio whe faults i its operatio occur. This ca be achieved by esurig that the scaed output is ot produced by a sigle programmable cotroller or persoal computer-based device but by a umber of cotrol devices workig together. Sca-failure detectio devices that effect automatic system shutdow i the shortest reasoably practicable time. Shutdow speeds of o more tha a few millisecods should be readily achievable. Beam bright-ups that are either removed by maskig, which itercepts them at the deflectio agles at which they occur, or projected at locatios that are iaccessible. 106 Istallatios iteded to sca audieces should always be supervised. 107 The choice of exposure time base for applicable MPE value determiatio is flexible but, oetheless, should be justifiable. It should ot be less tha the maximum possible time a perso could be exposed to a accessible emissio The radiatio safety of lasers used for display purposes Page 22 of 34

23 durig ormal operatio or followig a fault coditio. I most situatios this will be either the time take for the safety related cotrol system to detect a fault ad termiate emissio or the time take for maual itervetio to be effected (see Table 1). 108 Demostratio of a istallatio s ability to achieve compliace with the applicable MPE value whe scaig fails should be based upo measuremet ad computatio of worst-case exposure coditios. 109 Desigig ad costructig display laser istallatios to esure that sigle compoet failure does ot cause hazardous accessible emissios should always be cosidered as reasoably practicable safety provisio for audiece scaig applicatios. Istallatios that caot meet this criteria should ot be used for such purposes. Simultaeous exposures 110 Display laser istallatio safety assessmet should take accout of circumstaces i which separate sources could be viewed simultaeously. For visible emissios, the sum of the ratios of accessible emissios at the viewig poit to their respective applicable MPE values should ot exceed uity. This is illustrated by the followig equatio. Exposure(1) Exposure () < MPE (1) MPE () Key poits Audieces ad members of the public may be at risk of eye ijury if they directly view statioary laser beams that exceed 1 milli-watt radiat power or beams scaed across the eye that have ot bee determied as safe either by calculatio or measuremet. Factors that affect this risk iclude: (a) (b) (c) (d) the accessibility of hazardous laser beams; the power desity of accessible laser beams; the type of beam projectio, ie whether scaed or static; ad whether it is reasoable to assume that exposed people will have blik reflexes ad will ot deliberately stare at laser beams. Display laser istallatios that are potetially hazardous should be subjected to thorough safety assessmet before they are used. The issues that eed to be addressed are: (a) (b) (c) (d) whether laser beams are iteded to be viewed or whether they are oly likely to be viewed iadvertetly or followig istallatio malfuctio; evaluatio of the safety of laser beams that are iteded to be viewed, especially scaed emissios projected at audieces; restrictio of persoal access to potetially hazardous beams (ie those that are ot iteded to be viewed); ad the cosequeces for viewig safety whe istallatio malfuctio occurs ad of the exposure risks such failures preset to audieces ad members of the public. The radiatio safety of lasers used for display purposes Page 23 of 34

24 Display laser istallatios may be hazardous to employees ivolved i their calibratio or commissioig. Users ad istallers should kow what the hazards are ad have assessed the risks their employees face. Traiig, supervisio, safe systems of work, ad protective eyewear provisio are the importat issues to cosider. Laser-iduced eye damage is always permaet ad, depedig o which part of the retia the laser beam is focused, may cause loss of peripheral visio, readig disability or total loss of sight i the affected eye. The radiatio safety of lasers used for display purposes Page 24 of 34

25 Appedix A Defiitios Aperture, aperture stop A opeig i the protective housig or other eclosure of a laser product or system through which accessible laser radiatio is emitted. Applicable Maximum Permissible Exposure value (MPE) The exposure limit, determied by display laser istallatio safety assessmet, which whe complied with assures accessible emissio viewig safety. Appedix C gives curret MPE values. The MPE value that satisfies this criterio will deped o: (a) (b) (c) The wavelegth of laser emissio beig cosidered. The viewig coditio which applies to the accessible emissio, ie whether the beam is viewed directly or followig diffuse reflectio ad whether it is scaed, pulsed or cotiuous wave. The applicable exposure time base. This should be based o a fully justifiable assessmet of the maximum time ay perso ca or is likely to view a accessible emissio. I this regard, it may be justifiable to assume that xposure will be curtailed by eye aversio resposes ad/or automatic emergecy shutdow devices. For scaed, pulsed ad modulated lasers, the MPE for wavelegths from 400 m to 10 6 m is determied by usig the most restrictive of requiremets (a), (b) ad (c). The MPE for ocular exposure at other wavelegths or exposure of ski is determied by usig the most restrictive of requiremets (a) ad (b). (a) (b) (c) The exposure from ay sigle pulse withi a pulse trai shall ot exceed the MPE for a sigle pulse. The average exposure for a pulse trai of duratio T shall ot exceed the MPE for a sigle pulse of duratio T. The exposure from ay sigle pulse withi a pulse trai shall ot exceed the MPE for a sigle pulse multiplied by the correctio factor C 5. MPE trai = MPE sigle x C 5 where: MPE trai = MPE for ay sigle pulse i the pulse trai MPE sigle = MPE for a sigle pulse C 5 = N -1/4 N = umber of pulses expected i a exposure I some cases this value may fall below the MPE that would apply for cotiuous exposure at the same peak power usig the same exposure time. Uder these circumstaces the MPE for cotiuous exposure may be used. Aversio resposes (of the eye) Bright light sources cause the eye to be averted out of the emissio. This atural respose ivolves a umber of reflexes such as blikig, squitig ad head movemet ad is assumed i the curret British Stadard to take up to 0.25 The radiatio safety of lasers used for display purposes Page 25 of 34

26 secods. Therefore, eye aversio resposes do ot provide protectio agaist viewig emissios that ca damage the eye i less tha this time. Beam divergece The mea plae agle of the coe draw aroud the laser beam axis that, i ay cross-sectio, ecloses 63%* of the total beam power or eergy. Beam divergece i radias may be calculated usig the followig formula: (d 2 d 1 ) x Where d 1 ad d 2 are beam diameters, determied at locatios o the beam axis, separated by distace x. * For a gaussia beam profile, this is the circumferece aroud the beam axis at which emissio itesity falls to 1/e of the value at the cetre of the beam. The diameter of ay such cross-sectio at a particular distace from the laser aperture defies the beam diameter at that locatio. Collateral radiatio Ay electromagetic radiatio, i the wavelegth rage 180 m to 1 mm, except laser radiatio emitted as result of or ecessary for the operatio of a laser product. Cotiuous wave (CW) The output from a laser operatig i a cotiuous rather tha a pulsed mode. This icludes ay laser emissio havig a pulse legth that exceeds 0.25 secods. Diffractio gratig A optical compoet that splits a emissio ito a umber of beams or figers of light. Whe used i cojuctio with diffusely reflective or trasmissive optics, a broad swathe of light or wash effect, ofte multicoloured, ca be produced. Diffractio effects may be projected statically or scaed. Diffuse reflectio Chage i the spatial distributio of a beam of radiatio whe it is scattered i may directios by a surface. A perfect diffuser destroys all correlatio betwee the directio of the icidet ad emerget radiatio. Direct ocular viewig Exposure of the eye directly, or after specular reflectio, to all or part of a laser beam. Display laser istallatio Ay laser product that is desiged to project static or scaed emissios at imagig screes or ito free space for the purpose of etertaimet, ad which achieves this by either itegral ad/or exteral optical compoets. The term display laser istallatio is used throughout this guidace. It refers to the istallatio as a whole ad icludes the laser system, the effects head, ay exteral optical compoets such as mirrors ad mirror-balls, ad ay other devices or compoets which form part of laser display equipmet. Laser systems as defied are also themselves used for display purposes ad i this respect the term display laser istallatio icludes such usage. Effects gobo A optical processig device, commoly foud i covetioal etertaimets lightig equipmet, but which is fidig icreasig applicatio i display laser istallatios. The radiatio safety of lasers used for display purposes Page 26 of 34

27 They are usually located withi the effects head itself ad cosist of a umber of emissio processig elemets, such as coloured filters, diffractio gratigs ad beam maskig, mouted circumferetially o a servo-drive disc. The disc is positioed withi the laser emissio so that its rotatio by the servo is perpedicular to the emissio s directio (Figure 6 o page 17). I this way emissio processig ca be switched betwee the various optical elemets mouted o the disc. Effects head A arragemet of optical processig compoets such as scaig devices, mirrors, filters ad diffractio gratigs that usually forms a itegral part of the laser system icorporated withi a display istallatio. Laser system with itegral effects head To display area Rigid moutig Relatioal Azimuth scaer Figure 8 Effects head exteral Effective pulse legth (EPL) Used i scaed emissio MPE evaluatio. Numerically equal to the time take for a scaed emissio to completely traverse the 7 mm limitig aperture of the eye. Exteral optical compoet Ay optical processig device that forms part of a display laser istallatio but which is located or mouted exterally to the icorporated laser system ad ay associated effects head. Iterlockig device (iterlocks) Mechaical, electrical or other type of device which makes the operatio of a display laser istallatio depedet o the correct operatio of oe or more other parts of the istallatio. Display istallatio iterlocks form a itegral part of safety related cotrol systems. Laser product (6) Ay product or assembly of compoets that costitutes, icorporates or is iteded to icorporate a laser or laser system ad that is ot supplied by aother maufacturer for use as a compoet (or replacemet for such a compoet) of a electroic product. Laser system (6) A laser i combiatio with a appropriate laser eergy source, with or without additioal icorporated compoets. NB The curret British Stadard icludes light emittig diodes (LEDs) i the defiitio of a laser. This is because may high power desigs are capable of producig retial image power desities comparable with that produced by a laser. The radiatio safety of lasers used for display purposes Page 27 of 34

28 Maximum Permissible Exposure value (MPE) Laser radiatio persoal exposure limit for a particular viewig coditio. The curret British Stadard icludes tabulatios of these values. See Appedix C. Mirror-ball A type of exteral optical compoet cosistig of a array of small mirrors mouted o a sphere, which may be power drive at a few revolutios per miute. Operator A employee who has actual cotrol of the operatio of a display laser istallatio ad whose legal resposibilities are essetially those of Sectio 7 of the Health ad Safety at Work etc Act Programmable cotroller (PC) A software cotrolled, programmable electroic device used i machiery ad process cotrol applicatios. A display laser istallatio is a example of equipmet that requires a great deal of this type of cotrol to be able to project sophisticated sca patters. Pulse repetitio rate (PRF) Normally the umber of pulses emitted by a laser product per uit time. But, for the purposes of this guidace, the PRF is also the umber of beam passes or scas per uit time occurrig at a particular viewig or measuremet poit. PRF is specified as a frequecy, ormally i hertz (Hz). Pyramidal spier A rotatig array of small plae mirrors mouted i the form of a pyramid or trucated pyramid. Safety assessmet A critical examiatio of the desig, costructio ad operatioal features of a display laser istallatio, sufficietly comprehesive to esure that all radiatio hazards ad persoal exposure risks are idetified ad provisio made for their cotrol. Safety related cotrol systems (SRCS) A electroic ad/or mechaical device capable of automatic detectio of a potetially hazardous fault coditio ad actio to mitigate its cosequeces. A example of such a cotrol system would be oe that effects automatic emissio termiatio followig sca-failure detectio. Specular reflectio A reflectio from a surface that maitais correlatio betwee icidet ad reflected beams of radiatio, as with reflectios from a mirror, for example. The radiatio safety of lasers used for display purposes Page 28 of 34

29 Appedix B Types of display laser Table 2 Laser type Mai wavelwgths (m) Other wavelegths (m) Argo-io Copper vapour Dye Helium-Cadmium Helium-Neo Krypto-io Mixed gas 1 Neodymium-YAG 488 (blue/gree) ad (gree) ad Various (blue) (red) (red) 1064 (ifrared) (blue) ad (blue) 325 (Ultraviolet) (yellow/gree) ad (red) (See Argo ad Krypto-io spectral lies) Frequecy doubledd to 532 (yellow/ gree) 1 Used extesively i large istallatios to produce full colour displays. Helium-Neo (He-Ne) lasers producig red light with output powers typically up to 10 mw (Class 3B) are commoly used with scaig optics to produce movig geometrical patters, such as Lissajous figures or writig o screes, at smaller veues. Argo lasers, producig blue/gree light, are used i may situatios where higher powers are required. Udivided beams emitted from such lasers are ofte scaed by persoal computer or PC cotrolled servo-mouted optics (ofte referred to as galvos ). Powers ragig betwee 0.05 ad 4 watts are frequetly foud i discotheques ad clubs whereas outdoor displays may use systems capable of emittig tes of watts. Krypto lasers (ofte tes of watts), producig pricipally red but also yellow ad gree light, are frequetly used with or i place of Argo lasers i situatios where high power is eeded to project emissios over large distaces. Outdoor display istallatios are a example of such applicatios. Dye lasers (typically up to a few watts) may also be met occasioally. They are ofte used i cojuctio with Argo lasers. Although such lasers could be used i stageshows ad ightclubs, they are ot yet commoplace at these veues. But their ability to produce emissios of ay colour will udoubtedly esure their icreasig developmet ad use. The radiatio safety of lasers used for display purposes Page 29 of 34

30 1050 to x 10 6 C 6 C 7 W.m -2 5 x 10-2 C 6 C 7 J.m t 0.75 C 6 C 7 J.m -2 16C 6 C 7 W.m -2 Health ad Safety Appedix C MPE Data This appedix cotais data abstracts from the British Stadard (6) relevat to safety assessmet. Wavelegth y (m) Exposure time t (s) 10-9 <10-9 to to 1.8 x x 10-5 to 5 x x 10-5 to 1 x x 10-3 to to to to 3 x to J.m -2 3 x W.m to C 1 J.m -2 (t<t 1 ) C 1 J.m -2 (t>t 1 ) C 1 J.m to 400 C 1 J.m J.m W.m to C 6 J.m C 6 W.m to x 10 6 C 6 W.m -2 5 x 10-3 C 6 J.m -2 18t 0.75 C 6 J.m C 3 C 6 J.m -2 (t>t 2 ) 18t 0.75 C 6 J.m- 2 (t<t 2 ) 10-2 C 3 C 6 W.m to x 10 6 C 4 C 6 W.m -2 5 x 10-3 C 4 C 6 J.m t 0.75 C 4 C 6 J.m C 4 C 6 W.m to W.m J.m t 0.25 J.m to W.m J.m to W.m J.m t 0.25 J.m W.m to W.m J.m t 0.25 J.m -2 Table 3 Maximum permissable exposure (MPE) at the corea for direct ocular exposure to laser radiatio (m = aometres, s = secods) NB For correctio factors ad uits, see Table 6. Exposure time t (s) Wavelegth y (m) < to to to to 3 x to x W.m -2 30J.m to 315 C 2 J.m -2 C1J.m-2 (t>t 1 ) (t<t 1 ) C 2 J.m to 400 C 1 J.m J.m -2 10W.m to x W.m J.m J.m W.m to x C 4 W.m C 4 J.m C 4 J.m C 4 W.m to W.m J.m W.m -2 (3) 1 For correctio factors ad uits see Table 6. 2 There is oly limited evidece about effects for exposures of less tha 10-9 s. The MPEs for these exposure times have bee derived by maipulatig the irradiace applyig at 10-9 s. 3 For exposed ski areas greater tha 0.1m 2, the MPE is reduced to 100 W.m -2 Betwee 0.01 m 2 ad 0.1 m 2, the MPE varies iversely proportioal to the irradiated ski area. Table 4 Maximum permissable exposure (MPE) of ski to laser radiatio The radiatio safety of lasers used for display purposes Page 30 of 34

31 Spectural regio Duratio Aperture diameter for (m) (s) Eye (m) ski (m) 180 to to to to to 10 6 t 3 x 10 4 t 3 x 10 4 t 3 t>3 t 3 x 10 4 v v v v Table 5 aperture diameter applicable to measurig laser irradiace ad radiat exposure Parameter C 1 = 5.6x10 3 t 0.25 T 1 = ( -295) x y s y 0.2( -295) C 2 =10 T 2 = 10 x ( -550) y s C 3 = 10 C 4 = 10 C 4 = 5 C 5 =N -1/4 * y 0.015( -550) 0.002( y-700) C 6 = 1 for a a mi C 6 = a / a mi for a < a mi C 7 = ( -1150) y C 7 = 10 C 7 = 8 v Spectral regio (m) to to to to to to to to to to to to to 1400 * C 5 is oly applicable to pulse duratios shorter tha 0.25s. Table 6 MPE coefficiets Note to table 6 For exteded source laser radiatio (eg diffuse reflectio viewig) at wavelegths from 400 m to 1400 m, the itrabeam viewig MPEs ca be icreased by the followig factor (C 6 ) provided that the agular subtese of the source (measured at the viewer s eye) is greater tha a mi where: a = 1.5 mrad for t<0.7s mi a = mrad for 0.7s t<10s mi 2t3/4 a = 11 mrad for t 10s mi V V The radiatio safety of lasers used for display purposes Page 31 of 34

32 Appedix D Cotacts Civil Aviatio Authority Gatwick RH6 0YR Tel: Fax: Local Authority Evirometal Health Departmet (address i phoe book) BSI Iformatio Poit 389 Chiswick High Road Lodo W4 4AL Tel: The radiatio safety of lasers used for display purposes Page 32 of 34

33 Refereces 1 Health ad Safety at Work etc Act HMSO ISBN Maagemet of Health ad Safety at Work. Maagemet of Health ad Safety at Work Regulatios Approved Code of Practice HSE Books ISBN Work equipmet. Provisio ad Use of Work Equipmet Regulatios Guidace o Regulatios HSE Books ISBN Persoal protective equipmet at work. Persoal Protective Equipmet at Work Regulatios Guidace o Regulatios HSE Books ISBN Health ad Safety (Eforcig Authority) Regulatios 1989 (SI 1989 No 1903) 6 Safety of laser products. Part 1. Equipmet classificatio, requiremets ad user s guide British Stadard BSEN :1994 (Amedmet No1) ISBN This is a dual umbered stadard which implemets Europea stadard EN :1994 i the UK. This stadard is revised periodically but the series umber is likely to remai uchaged. Readers should refer to the most up-to-date versio whe usig this guidace. BSEN60825:1992 which excludes light emittig diodes (LEDs), remais extat util Guide to health, safety ad welfare at pop cocerts ad similar evets Health ad Safety Commissio/Home Office/The Scottish Office HMSO ISBN EEC Coucil Directive 89/392/EEC as ameded by 91/368/EEC Machiery Safety Directive 9 EN292-1:1991 Safety of machiery - Basic cocepts, geeral priciples for desig. Part 1: Basic termiology, methodology EN292-2:1991/A1: 1995 Safety of machiery - Basic cocepts, geeral priciples for desig. Part 2: Techical priciples ad specificatios 10 5 Steps to risk assessmet 1994 HSE Books IND(G)163L Available i priced packs ISBN Cotrollig safety of display laser istallatios 1996 HSE Books IND(G)224L 12 Safety with Lasers ad Other Optical Sources D Sliey, M Wolbarsht 1980 Pleum Press New York ISBN Lasers, festival ad etertaimet lightig code Istitutio of Lightig Egieers Safety of laser products. Part 3. Guidace for laser displays ad shows IEC 825-3:1995 The radiatio safety of lasers used for display purposes Page 33 of 34

34 Further iformatio For iformatio about health ad safety rig HSE s Ifolie Tel: Fax: Textphoe: [email protected] or write to HSE Iformatio Services, Caerphilly Busiess Park, Caerphilly CF83 3GG. HSE priced ad free publicatios ca be viewed olie or ordered from or cotact HSE Books, PO Box 1999, Sudbury, Suffolk CO10 2WA Tel: Fax: HSE priced publicatios are also available from bookshops. British Stadards ca be obtaied i PDF or hard copy formats from the BSI olie shop: or by cotactig BSI Customer Services for hard copies oly Tel: [email protected]. The Statioery Office publicatios are available from The Statioery Office, PO Box 29, Norwich NR3 1GN Tel: Fax: [email protected] Website: (They are also available from bookshops.) Statutory Istrumets ca be viewed free of charge at Published by HSE 02/10 Page 34 of 34