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Guide | Ultraviolet | Laser
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Contract VC/2007/0581
© Health Protection Agency
Centre for Radiation, Chemical and Environmental Hazards
Chilton, Didcot, Oxfordshire OX11 0RQ
A Non-Binding Guide to the Artificial Optical
Radiation Directive 2006/25/EC
Radiation Protection Division, HeaIth Protection Agency
This Guide was funded by the European Commission Employment, Social Affairs and Equal Opportunities DG,
under contract number VC/2007/0581.
1.1 How to use this Guide 2
1.2 ReIationship with Directive 2006/25/EC 3
1.3 Scope of the Guide 4
1.4 Pertinent reguIations and further information 4
1.5 OfficiaI and non-officiaI advice centres 5
2 Sources of ArtificiaI OpticaI Radiation 5
2.1 Sources of Non-Coherent Radiation 5
2.1.1 Work activities 5
2.1.2 Applications 6
2.2 Sources of Laser Radiation 8
2.3 TriviaI sources 10
3 HeaIth Effects from Exposure to OpticaI Radiation 11
4 Requirements of the ArtificiaI OpticaI Radiation Directive 12
4.1 ArticIe 4 - Determination of exposure and assessment of risks 13
4.2 ArticIe 5 - Provisions aimed at avoiding or reducing risks 15
4.3 ArticIe 6 - Worker information and training 15
4.4 ArticIe 7 - ConsuItation and participation of workers 15
4.5 ArticIe 8 - HeaIth surveiIIance 15
4.6 Summary 15
5 Use of Exposure Limits 16
5.1 Laser ELVs 16
5.2 Non-Coherent OpticaI Radiation 18
5.3 References 21
6 Risk Assessment in the Context of the Directive 22
6.1 Step 1. Identifying hazards and those at risk 22
6.2 Step 2. EvaIuating and prioritising risks 23
6.3 Step 3. Deciding on preventive action 24
6.4 Step 4. Taking action 24
6.5 Step 5. Monitoring and reviewing 25
6.6 References 25
7 Measurement of OpticaI Radiation 25
7.1 Requirements under the Directive 25
7.2 Seeking further assistance 26
8 Use of Manufacturers' Data 26
8.1 Safety cIassification. 27
8.1.1 Laser safety classification. 27
8.1.2 Safety classification of non-coherent sources 30
8.1.3 Safety classification of machinery 33
8.2 Hazard distance and hazard vaIues information 33
8.2.1 Lasers - Nominal Ocular Hazard Distance 33
8.2.2 Broad-band sources ÷ Hazard Distance and Hazard Value 34
8.3 Further usefuI information 34
9 ControI measures 35
9.1 Hierarchy of controI measures 36
9.2 EIimination of the hazard 37
9.3 Substitution by Iess hazardous process or equipment 37
9.4 Engineering controIs 38
9.4.1 Access Prevention 38
9.4.2 Protection by Limiting Operation 39
9.4.3 Emergency Stops 39
9.4.4 Ìnterlocks 39
9.4.5 Filters and Viewing Windows 40
9.4.6 Alignment Aides 41
9.5 Administrative measures 41
9.5.1 Local Rules 42
9.5.2 Controlled Area 42
9.5.3 Safety signs and notices 43
9.5.4 Appointments 44
9.5.5 Training and Consultation 44
9.6 PersonaI Protective Equipment 47
9.6.1 Protection against other hazards 47
9.6.2 Eye protection 48
9.6.3 Skin protection 49
9.7 Further usefuI information 50
9.7.1 Basic standards 50
9.7.2 Standards by type of product 50
9.7.3 Welding 50
9.7.4 Laser 51
9.7.5 Ìntense light sources 51
10 Managing Adverse Incidents 51
11 HeaIth SurveiIIance 52
11.1 Who shouId carry out the HeaIth SurveiIIance? 52
11.2 Records 52
11.3 MedicaI Examination 53
11.4 Actions if an exposure Iimit is exceeded 53
APPENDIX A Nature of OpticaI Radiation 54
APPENDIX B BioIogicaI effects of opticaI radiation to the eye and the
skin 56
B1 The Eye 56
B2 The Skin 57
B3 Biological effect of different wavelength to the eye and the
B3.1 Ultraviolet radiation: UVC (100÷280nm); UVB (280÷315nm);
UVA (315-400 nm) 58
B3.2 Visible radiation 59
B3.3 ÌRA 60
B3.4 ÌRB 60
B3.5 ÌRC 61
APPENDIX C ArtificiaI OpticaI Radiation Quantities & Units 62
C1 Fundamental quantities 62
C1.1 Wavelength 62
C1.2 Energy 62
C1.3 Other useful quantities 62
C1.4 Quantities used in exposure limits 63
C1.5 Spectral quantities and broad-band quantities 63
C1.6 Radiometric quantities and effective quantities 64
C1.7 Luminance 64
APPENDIX D Worked ExampIes 65
D1 Office 65
D1.1 Explanation of general method 65
D1.2 Format of examples 71
D1.3 Ceiling mounted fluorescent lamps behind a diffuser. 72
D1.4 A single ceiling mounted fluorescent lamp with no diffuser. 74
D1.5 A bank of ceiling mounted fluorescent lamps with no diffuser. 76
D1.6 A cathode ray tube visual display unit. 78
D1.7 A laptop computer display. 80
D1.8 An outdoor area floodlight incorporating a metal halide lamp. 82
D1.9 An outdoor area floodlight incorporating a compact fluorescent
lamp. 84
D1.10 An electronic insect killer. 86
D1.11 A ceiling mounted spotlight 88
D1.12 A desk mounted task light 90
D1.13 A 'daylight spectrum'desk mounted task light 92
D1.14 A photocopier 94
D1.15 A desktop digital data projector 96
D1.16 A portable digital data projector 98
D1.17 A digital interactive whiteboard 100
D1.18 A ceiling mounted recessed compact fluorescent lamp 102
D1.19 An indicator LED 104
D1.20 A PDA 106
D1.21 A UVA blacklight 108
D1.22 A streetlight incorporating a metal halide lamp 110
D1.23 Summary of data from examples 112
D2 Laser Show 114
D2.1 Hazards and People at Risk 114
D2.2 Evaluating and Prioritising Risk 115
D2.3 Deciding on preventive action and taking action. 116
D2.4 Monitoring and reviewing 116
D2.5 Conclusion 116
D3 Medical Applications of Optical Radiation 117
D3.1 Task Lighting 118
D3.2 Diagnostic lighting 120
D3.3 Therapeutic sources 121
D3.4 Specialist test sources 125
D4 Driving at work 127
D5 Military 130
D6 Gas-fired overhead radiant heaters 131
D7 Material Processing Laser 133
D7.1 Ìdentifying hazards and those at risk 133
D7.2 Evaluating and prioritising risks 134
D7.3 Deciding on preventive action 134
D8 Hot Ìndustries 135
D8.1 Steel processing 135
D8.2 Glass works 136
D8.3 Further Ìnformation 136
D9 Flash Photography 137
APPENDIX E Requirements Of Other European Directives 139
APPENDIX F Existing Member State LegisIation and Guidance 143
APPENDIX G European and InternationaI Standards 148
G1 Euronorms 148
G2 European Guidance 150
G3 ÌSO, ÌEC and CÌE Documents 151
APPENDIX H Resources 152
H1 Ìnternet 152
H1.1 Advisory/Regulatory 152
H1.2 Standards 153
H1.3 Associations/Web Directories 153
H1.4 Journals 154
H2 CD, DVD and other Resources 155
APPENDIX I GIossary 156
APPENDIX J BibIiography 160
J1 History of Lasers 160
J2 Medical Lasers 160
J3 Laser and Optical Radiation Safety 160
J4 Laser Technology and Theory 160
J5 Guidelines and Statements 160
APPENDIX K Text of Directive 2006/25/EC 162
TO BE ADDED BY EU 162
ÌNTRODUCTÌON
Directive 2006/25/EC (termed the Directive) covers all artificial sources of optical
radiation. Most of the requirements of the Directive are similar to existing requirements
of, for example, the Framework Directive 89/391/EEC. Therefore, the Directive should
place no greater burden on employers than is already required by other Directives.
However, since the Directive is so all-embracing, there is a need to identify
applications of artificial optical radiation that are so insignificant with regard to health,
that no further assessment is required. This guide is intended to give an indication of
such trivial applications, to provide guidance for a number of other specific
applications, present an assessment methodology and also, in some cases, suggest
that further assistance should be sought.
A number of industries have well-developed guidance covering specific applications of
optical radiation and references to such sources of information are made.
Artificial optical radiation covers a very wide range of sources that employees may be
exposed to in the workplace and elsewhere. These sources will include area and task
lighting, indicator devices, many displays and other similar sources which are essential
to the well-being of workers. Therefore, it is not reasonable to take a similar approach
to many other hazards by necessarily minimising the artificial optical radiation hazard.
To do so may increase the risk from other hazards or activities in the workplace. A
simple example of this is that turning the lights off in an office may put everyone in the
A range of artificial optical radiation sources are used as input to manufacturing
processes, for research and communication. Optical radiation also may be incidental,
such as when a material is hot and radiates optical radiation energy.
There are a number of applications of artificial optical radiation which require direct
exposure of employees at levels that may exceed the exposure limits given in the
Directive. These include some entertainment and medical applications. Such
applications will need critical assessments to ensure that the exposure limits are not
Artificial optical radiations are separated into laser and non-coherent radiation in the
Directive. This separation is only used in this Guide where there is a clear benefit in
doing so. The traditional view is that laser radiation exists as a beam of a single
wavelength. A worker can be very close to the beam path but suffer no adverse health
effects. However, if they get directly into the beam then they may immediately exceed
the exposure limit. For non-coherent radiation, the optical radiation is less likely to be a
well collimated beam and the level of exposure increases as the source is approached.
Ìt could be claimed that with a laser beam, the probability of being exposed is low, but
the consequence may be severe; for a non-coherent source, the probability of
exposure may be high, but the consequence less severe. This traditional distinction is
becoming less obvious with some evolving optical radiation technologies.
A NON-BÌNDÌNG GUÌDE TO THE ARTÌFÌCÌAL OPTÌCAL RADÌATÌON DÌRECTÌVE 2006/25/EC
The Directive was adopted under Article 137 of the Treaty establishing the European
Community, and this Article expressly does not prevent Member States from
maintaining or introducing more stringent protective measures compatible with the
1.1 How to use this Guide
Artificial optical radiations exist in most workplaces. Many present little or no risk of
causing injury and some allow work activities to be carried out safely.
This Guide should be read in conjunction with Directive 2006/25/EC (the Directive) and
the Framework Directive 89/391/EEC.
Directive 2006/25/EC lays down the minimum safety requirements regarding the
exposure of workers to risks arising from artificial optical radiation. Article 13 of this
Directive requires the Commission to draw up a practical guide to the Directive.
The Guide is primarily intended to assist employers, and in particular small and
medium-sized enterprises. However, it may also be useful for employee
representatives and regulatory authorities in Member States.
The Guide falls naturally into three sections:
All employers should read the Sections 1 and 2 of this Guide.
If all of the sources in the workplace are included in the list of trivial sources in section
2.3, there is no need for further actions.
Where sources not listed in section 2.3 are present, risk assessment will be more
complex. The employer should additionally consider Sections 3-9 of this Guide.
This should inform a decision on whether to carry out self-assessment or to seek
external assistance.
The appendices contain further information which may be useful for employers who
are carrying out risk assessments themselves.
Data from product manufacturers may help the employer with their risk assessment. Ìn
particular, some types of artificial optical radiation source should be classified to
provide an indication of the accessible optical radiation hazard. Ìt is suggested that
employers should request appropriate information from the suppliers of sources of
artificial optical radiation. Many products will be subject to the requirements of
European Community Directives, for example for CE marking, and a specific reference
to this is made in paragraph (12) of the preamble to the Directive (see Appendix K).
Chapter 8 of this Guide provides guidance on the use of manufacturers' data.
All workers are exposed to artificial optical radiation. Examples of sources are given in
Chapter 2. One of the challenges is to ensure that sources that may present a risk of
exposing workers to levels in excess of the exposure limit values are adequately
assessed without the burden of having to assess the majority of sources that do not
present a risk under reasonably foreseeable circumstances ÷ the so-called "trivial¨
This Guide aims to lead users through a logical path for assessing the risk from
exposure of workers to artificial optical radiation:
Ìf the only sources of exposure to artificial optical radiation are trivial, no further action is required.
Some employers may wish to record that they have reviewed the sources and made this
Ìf sources are not trivial or the risk is unknown, employers should follow a process to assess the
risk and implement appropriate control measures, if necessary.
Chapter 3 of this Guide outlines the potential health effects.
Chapter 4 describes the requirements of the Directive and the exposure limit values are presented
in Chapter 5. These two Chapters therefore cover the legal requirements.
Chapter 6 contains a suggested methodology for carrying out the risk assessment. Ìt is possible
that the conclusion is that there is no risk, so the process stops here.
Where inadequate information exists to carry out the risk assessment, it may be necessary to
undertake measurements (Chapter 7) or make use of manufacturers' data (Chapter 8).
Chapter 9 covers control measures where it is necessary to reduce the risk.
Should someone get exposed to artificial optical radiation at levels in excess of the exposure limit
values then Chapter 10 covers contingency plans and Chapter 11 covers health surveillance.
The Appendices provide further information for employers and others who may be
involved with the risk assessment process:
A ÷ Nature of optical radiation
B ÷ Biological effects of optical radiation to the eye and the skin
C ÷ Artificial optical radiation quantities and units
D ÷ Worked examples. Some of the examples in this Appendix provide the justification for specific
sources being classed as trivial.
E ÷ Requirements of other European Directives
F ÷ Existing Member State legislation and guidance
G ÷ European and international standards
H ÷ Resources
Ì ÷ Glossary
J ÷ Bibliography
K ÷ Text of Directive 2006/25/EC
1.2 ReIationship with Directive 2006/25/EC
Ìn accordance with Article 13 of Directive 2006/25/EC of the European Parliament and
of the Council on the minimum health and safety requirements regarding the exposure
of workers to risks arising from artificial optical radiation, this Guide addresses Articles
4 (Determination of exposure and assessment of risk) and 5 (Provisions aimed at
avoiding or reducing risks), and Annexes Ì and ÌÌ (exposure limit values for non-
coherent radiation and laser radiation, respectively) of the Directive (see Appendix K).
Guidance is also provided on other Articles of the Directive.
TabIe 1.1 ReIationship between ArticIes of the Directive and sections of this Guide
ArticIes of Directive
2006/25/EC
TitIe Sections of the Guide
ArticIe 2 Definitions Appendix Ì
ArticIe 3 Exposure limit values Chapters 6, 7, 8, and 9
ArticIe 4 Determination of exposure and
ArticIe 5 Provisions aimed at avoiding or reducing
ArticIe 6 Worker information and training Chapter 9
ArticIe 7 Consultation and participation of workers Chapter 9
ArticIe 8 Health surveillance Chapter 11
1.3 Scope of the Guide
This Guide is intended for all undertakings where workers may be exposed to artificial
optical radiations. The Directive does not provide a definition for artificial optical
radiations. Sources such as volcanic eruptions, the sun and reflected solar radiation
from, for example, the moon are clearly excluded. However, there may be a number of
sources that are ambiguous. Would a fire started by human action be considered an
artificial source, but one started by lightning not?
The Directive does not specifically exclude any artificial optical radiation source.
However, many sources, such as indicator lights on electrical equipment, will be trivial
sources of optical radiation. This Guide provides a list of sources that can be
generically assessed as not likely to exceed the exposure limit values.
There will be some potential worker exposure scenarios which are complex and
therefore beyond the scope of this Guide. Employers should seek further advice on
assessing complex exposure scenarios.
1.4 Pertinent reguIations and further information
Use of this Guide does not of itself ensure compliance with statutory artificial optical
radiation protection requirements in the various EU Member States. The authoritative
instruments are the rules of law by which the Member States have transposed
Directive 2006/25/EC. These may go beyond the minimum requirements of the
Directive, on which this Guide is based.
As a further aid to implementing the requirements of the Directive, manufacturers may
manufacture equipment emitting artificial optical radiation to European standards.
SOURCES OF ARTÌFÌCÌAL OPTÌCAL RADÌATÌON
References are made to relevant standards in this Guide. Such standards may be
obtained from the national standardisation institutions against payment.
Further information can be obtained from the national regulations and standards and
the pertinent literature. Appendix F contains references to individual publications by the
competent Member State authorities. However, inclusion of a publication in the
Appendix does not mean that all of the contents are entirely consistent with this Guide.
1.5 OfficiaI and non-officiaI advice centres
Where this Guide does not answer questions arising on how to fulfil the artificial optical
radiation protection requirements, the national resources should be contacted directly.
They include labour inspectorates, accident insurance agencies or associations and
chambers of commerce, industry and craft trades.
2 SOURCES OF ARTIFICIAL OPTICAL RADIATION
2.1 Sources of Non-Coherent Radiation
SIow time-varying fieIds
ELF VF VLF LF
RF FieIds
Radiowaves Microwaves
100 000 km 100 km 100 m 10 cm 0,1 mm Wave-
Iength
400 nm 700 nm
OpticaI Radiation
IR Light UV
|on|s|ng
Rad|at|on
2.1.1 Work activities
Ìt is difficult to think of an occupation that does not involve, at some point, exposure to
artificially generated optical radiation. Everyone who works in an indoor environment is
likely to be exposed to optical emissions from lighting and computer screens. Outdoor
workers may require some form of task lighting when natural illumination is insufficient.
Persons travelling during the course of the working day are quite likely to be exposed
to artificial illumination, even if this is merely exposure to lights from other persons'
vehicles. All of these are artificially generated forms of optical radiation and so may be
taken to fall within the scope of the Directive.
Apart from ever-present sources, such as lighting and computer screens, artificial
optical radiation may be produced either deliberately, as a necessary part of some
process, or else adventitiously, that is as an unwanted by-product. For example, in
order to induce fluorescence in a penetrant dye, it is necessary to produce ultra-violet
radiation and expose the dye to it. On the other hand, the production of copious ultra-
violet during arc welding is in no way essential to the process ÷ although it is
Whether optical radiation is produced deliberately for use or as an unintended by-
product of a process, it is still necessary to control exposure to it, at least to the degree
set out in the Directive. Artificially generated optical radiation is present in most
workplaces, but particularly in the following types of industry:
Hot industries, such as glass and metal working, where furnaces emit infra-red
Print industries, where inks and paints are often set by the process of photo-
induced polymerisation
Art and entertainment, where performers and models may be directly illuminated by
spotlights, effect lighting, modelling lights and flashlamps
Entertainment, where the workers in the audience area may be illuminated by
general and effect lighting
Non-destructive testing, which may involve the use of ultraviolet radiation to reveal
Medical treatment, where practitioners and patients may be exposed to operating
theatre spot lighting and to therapeutic use of optical radiation
Cosmetic treatment, which makes use of lasers and flashlamps, as well as
ultraviolet and infrared sources
Shop-floor and warehousing industries, where large open buildings are illuminated
by powerful area lights
Pharmaceuticals and research, where ultraviolet sterilisation may be in use
Sewage treatment, where ultraviolet sterilisation may be in use
Research, where lasers may be in use and ultraviolet induced fluorescence may be
Metal working involving welding
Plastics manufacturing involving laser bonding
The above list is not intended to be exhaustive.
2.1.2 AppIications
The table below gives some idea of the sorts of uses that different spectral regions
have. Ìt is also intended to indicate what spectral regions may be present despite their
not being needed for a particular process. The spectral regions are described in
WaveIength
Used for AdventitiousIy produced during
Germicidal sterilisation
Fluorescence (laboratory)
Ìnk curing
Some area and task lighting
Some projection lamps
Fluorescence (laboratory, non-destructive
testing, entertainment effects, crime detection,
forgery detection, property marking)
Ìnsect traps
Area and task lighting
VisibIe
Ìndicator lamps
Hair and thread vein removal
TV and PC screens
Some heating/drying applications
Surveillance illumination
Some of the spectral regions that are listed as adventitiously produced may only be
emitted in fault conditions. For example, certain types of floodlights are based on a
high pressure mercury discharge lamp. This produces radiation in all spectral regions,
but it is usually enclosed by an outer envelope which prevents significant emission of
UVB and UVC. Ìf the envelope is broken, and the lamp continued to function, it will
emit hazardous levels of UV radiation.
2.2 Sources of Laser Radiation
The laser was first successfully demonstrated in 1960. Ìnitially lasers tended to be
confined to research and military applications. They were usually operated by the
people who designed and built them, and these same people were at risk from the
laser radiation. However, the laser is now truly ubiquitous. They are used in many
applications in the workplace, sometimes in equipment where the laser radiation is
controlled by effective engineering means so that the user does not need to know that
the equipment contains a laser.
Lasers beams are usually characterised as being of a single, or small number of,
discrete wavelengths; the emission has low divergence, so approximately maintaining
the power or energy within a given area over considerable distances; and the laser
beam is coherent, or the individual waves of the beam are in step. Laser beams can
usually be focussed to a small spot with the potential to cause injuries and damage to
surfaces. These are all generalisations. There are lasers that produce laser beams
over a wide wavelength spectrum; there are devices that produce widely divergent
beams; and some laser beams are not coherent over most of their path length. Laser
beam emissions may be continuous, termed continuous wave (CW) or they may be
pulsed.
Lasers are categorised on the basis of the "active medium¨ used to generate the laser
beam. This medium may be a solid, liquid or a gas. Lasers with a solid medium are
divided into crystal-type solids, termed solid state lasers, and semiconductor lasers.
The following table lists some typical lasers and the wavelengths emitted by them.
Type Laser PrincipaI
Helium Neon (HeNe) 632.8 nm CW up to 100 mW
Helium Cadmium (HeCd) 422 nm CW up to 100 mW
Argon Ìon (Ar)
488, 514 nm plus blue
CW up to 20 W
Krypton Ìon (Kr)
647 nm plus UV,
CW up to 10 W
10600 nm
(10.6 m)
Pulsed or CW up to 50
Nitrogen (N) 337.1 nm Pulsed > 40 J
Xenon chloride (XeCl)
Krypton fluoride (KrF)
Xenon fluoride (XeF)
Argon fluoride (ArF)
308 nm
Pulsed up to 1 J
Ruby 694.3 nm Pulsed up to 40 J
Neodymium:YAG (Nd:YAG)
1064 and 1319 nm
532 and 266 nm
Pulsed or CW up to TW,
100W average CW
Neodymium:Glass (Nd:Glass) 1064 nm Pulsed up to 150 J
Ytterbium (Yb) 1030 - 1120 nm CW up to kW
Ytterbium:YAG (Yb:YAG) 1030 nm CW up to 8000 W
10600 nm CW up to 8000 W
Various Materials ÷ e.g.
ÌnGaAsP
400 ÷ 450 nm
600 - 900 nm
1100 - 1600 nm
CW (some pulsed) up to
LIQUID (DYE)
Dye - Over 100 different laser
dyes act as laser media
300 - 1800 nm
Pulsed up to 2.5 J
CW up to 5 W
Further information on lasers can be found in the publications referenced in the
Bibliography in Appendix J.
The following is a summary of some laser applications.
Category ExampIe AppIications
Cutting, Welding, Laser marking, Drilling, Photolithography, Rapid
Distance measurement, Surveying, Laser velocimetry, Laser vibrometers,
Electronic speckle pattern interferometry, Optical fibre hydrophones, High
speed imaging, Particle sizing
Ophthalmology, Refractive surgery, Photodynamic therapy, Dermatology,
Laser scalpel, Vascular surgery, Dentistry, Medical diagnostics
Communications Fibre, Free-space, satellite
Optical Ìnformation Storage Compact disc/DVD, laser printer
Spectroscopy Substance identification
Holography Entertainment, information storage
Entertainment Laser shows, laser pointers
2.3 TriviaI sources
Appendix D of this Guide contains worked examples of some artificial sources of
optical radiation which may be common to many workplaces, for example shops and
offices. For each type of source which has been considered, because innumerable
examples of different designs of equipment will exist in the marketplace, it is not
possible here to create a comprehensive list which contains all existing optical
radiation sources and applications. Differences in, for example, the curvature of a
reflector, the thickness of a glass cover or the manufacturer of a fluorescent lamp can
have a considerable effect on the optical radiation produced by a source. Each
example is therefore, strictly speaking, unique to the particular type and model of
source which has been examined.
However, where a worked example shows that:
a particular source may be responsible for exposures which are only
a small fraction ( < 20%) of the Exposure Limits, or
a source may produce exposures in excess of the limits, but only in
extremely unlikely situations,
then normal exposure to sources of these types may be considered to present a trivial
risk to health, i.e. the source can be considered "safe¨.
The tables below present these common types of source in two groupings:
trivial (i.e. due to insignificant accessible emissions)
not hazardous in normal use (i.e. potential over-exposure only occurs in
unusual circumstances)
Where a workplace contains only those sources listed in these tables, and where they
are only used in the circumstances described, it may be considered that no further risk
assessment is necessary. Ìf these conditions are not satisfied, the person responsible
for safety should consider the information provided in the remainder of this Guide:
extensive appendices which contain more detail are also provided.
Sources only likely to produce insignificant exposures, which can be considered 'safe"
Ceiling mounted fluorescent lighting with diffusers over the lamps
Computer or similar display screen equipment
Ceiling mounted compact fluorescent lighting
Compact fluorescent floodlighting
UVA insect traps
Ceiling mounted tungsten halogen spotlighting
Tungsten lamp task lighting (including daylight spectrum bulbs)
Ceiling mounted tungsten lamps
HEALTH EFFECTS FROM EXPOSURE TO OPTÌCAL RADÌATÌON
Ìnteractive whiteboard presentation equipment
Ìndicator LEDs
Vehicle indicator, brake, reversing and foglamps
Photographic flashlamps
Gas-fired overhead radiant heaters
Sources not likely to present a health risk under specific circumstances
Source Circumstances for safe use
Ceiling mounted fluorescent lighting without
diffusers over the lamps
Safe at normal working illumination levels ( 600 lux)
Metal halide/high pressure mercury floodlighting Safe if front cover glass intact and if not in line of sight.
Desktop projectors Safe if beam not looked into
Low pressure UVA blacklight Safe if not in line of sight.
Any ¨Class 1¨ laser device (to EN 60825-1) Safe if covers intact. May be unsafe if covers removed
Any "Exempt Group¨ product (to EN 62471) Safe if not in line of sight. May be unsafe if covers removed
Vehicle headlights Safe if extended direct intra-beam viewing avoided
3 HEALTH EFFECTS FROM EXPOSURE TO OPTICAL
Optical radiation is absorbed in the outer layers of the body and, therefore, its
biological effects are mostly confined to the skin and eyes but systemic effects may
also occur. Different wavelengths cause different effects depending on which part of
the skin or eye absorbs the radiation, and the type of interaction involved:
photochemical effects dominate in the ultraviolet region, and thermal effects in the
infrared. Laser radiation can produce additional effects characterised by very rapid
absorption of energy by tissue, and is a particular hazard for the eyes where the lens
can focus the beam.
The biological effects can be broadly divided into acute (rapidly occurring) and chronic
(occurring as a result of prolonged and repeated exposures over a long time). Ìt is
generally the case that acute effects will only occur if the exposure exceeds a
threshold level, which will usually vary from person to person. Most exposure limits are
based on studies of thresholds for acute effects, and derived from statistical
consideration of these thresholds. Therefore, exceeding an exposure limit will not
necessarily result in an adverse health effect. The risk of an adverse health effect will
increase as exposure levels increase above the exposure limit. The majority of effects
described below will occur, in the healthy adult working population, at levels
substantially above the limits set in the Directive. However, persons who are
abnormally photosensitive may suffer adverse effects at levels below the exposure
Chronic effects often do not have a threshold below which they will not occur. As such,
the risk of these effects occurring cannot be reduced to zero. The risk can be reduced
÷ by reducing exposure ÷ and observance of the exposure limits should reduce risks
from exposure to artificial sources of optical radiation to levels below those which
society has accepted with respect to exposures to naturally occurring optical radiation.
WaveIength (nm) Eye Skin
100 ÷ 280 UVC
Photoconjunctivitis
280 ÷ 315 UVB
Elastosis (photoageing)
315 ÷ 400 UVA
Photoretinal damage
Ìmmediate Pigment Darkening
380 ÷ 780 VisibIe
(Blue Light Hazard)
780 ÷ 1400 IRA
1400 ÷ 3000 IRB
Cataracts Burn
3000 ÷ 10
Corneal burn Burn
4 REQUIREMENTS OF THE ARTIFICIAL OPTICAL RADIATION
The full text of the Directive is included in Appendix K of this Guide. This Chapter
provides a summary of the key requirements.
The Directive lays down the MÌNÌMUM requirements for the protection of workers from
risks to their health and safety arising or likely to arise from exposure to artificial optical
radiation during their work. Therefore, Member States may introduce, or already have
in place, more restrictive requirements.
REQUÌREMENTS OF THE ARTÌFÌCÌAL OPTÌCAL RADÌATÌON DÌRECTÌVE
4.1 ArticIe 4 - Determination of exposure and assessment of
The main emphasis of the Directive is that employers should ensure that workers are
not exposed to levels of artificial optical radiation in excess of the exposure limit values
contained within the Annexes of the Directive. Employers may be able to demonstrate
this through information supplied with sources, through generic assessments carried
out by themselves or others, by undertaking theoretical assessments or by doing
measurements. The Directive does not specify a methodology, so it is up to the
employer how this key objective is achieved. However, the employer is guided to
existing published standards and where this is not appropriate, to "available national or
international science-based guidelines¨.
Many of the requirements of the Directive are similar to those of Directive 89/391/EEC
and, as such, an employer already complying with the requirements of that Directive is
unlikely to require significant additional work to comply with this Directive. However,
when carrying out the assessment, the employer is required to give particular attention
to the following (Article 4, 3):
To be considered Comment
(a) the level, wavelength range and
duration of exposure to artificial
sources of optical radiation;
This is the fundamental information about the scenario considered.
Ìf the exposure level is significantly below the exposure limit that
would apply for exposure for a complete working day (assumed to
be 8 hours) then no further assessment is required unless exposure
to multiple sources are a concern. See (h).
(b) the exposure limit values referred
to in Article 3 of this Directive;
From the information in (a) it should be possible to identify the
applicable exposure limit values.
(c) any effects concerning the health
and safety of workers belonging to
particularly sensitive risk groups;
Ìt is suggested that the approach should be reactive rather than
proactive. There may be some workers who know that they are
particularly sensitive to flickering light, for example. The employer
should then consider whether modifications to the work activity can
be introduced.
(d) any possible effects on workers'
health and safety resulting from
workplace interactions between optical
radiation and photosensitising
chemical substances;
Ìt is suggested that employers should specifically consider the
possibility of photosensitisation from chemical substances used in
the workplace. However, as with (c), the employer may need to
react to issues raised by workers where the photosensitivity is
caused by chemical substances used outside of the workplace.
(e) any indirect effects such as
temporary blinding, explosion or fire;
Eye exposure to bright lights may be an issue for some work
practices. The normal aversion responses should provide a level of
protection at exposure levels below the exposure limit value.
However, the employer should consider sources of artificial optical
radiation that may cause distraction, dazzle, glare and afterimages,
where such exposures could compromise the safety of the worker
The optical radiation from some artificial optical radiation sources
may be capable of causing an explosion or a fire. This is
particularly relevant for Class 4 lasers, but should also be
considered for other sources, especially in environments where
flammable or explosive agents may be present.
(f) the existence of replacement
equipment designed to reduce the
levels of exposure to artificial optical
Ìt is suggested that this should be considered where the exposure
of workers to artificial optical radiation above the exposure limit
values is possible.
(g) appropriate information obtained
from health surveillance, including
published information, as far as
This information may come from within the employer's organisation,
from industry representative groups or from international
organisations such as the World Health Organisation and the
Ìnternational Commission on Non-Ìonizing Radiation Protection.
(h) multiple sources of exposure to
artificial optical radiation;
From the information obtained in (a) and (b), it may be possible to
determine the proportion of the exposure limit that will be provided
by each artificial optical radiation source. A simplified approach will
be to consider this for the number of sources that may expose
workers and add the proportions. Ìf the sum is less than one, then
the exposure limit values are unlikely to be exceeded. Ìf the sum
exceeds one then a more detailed assessment will be required.
(i) a classification applied to a laser as
defined in accordance with the
relevant CENELEC standard and, in
relation to any artificial source likely to
cause damage similar to that of a laser
of class 3B or 4, any similar
Class 3B and Class 4 laser products emit accessible laser radiation
that could lead to the exposure limit values being exceeded.
However, under some circumstances, lower hazard class lasers
may also need assessment. EN 62471 assigns non-laser artificial
optical radiation sources into a different classification scheme. Risk
Group 3 devices should be assessed, but consideration should also
be given to the likely exposure scenarios for lower Risk Groups.
(j) information provided by the
manufacturers of optical radiation
sources and associated work
equipment in accordance with the
relevant Community Directives.
Employers should request adequate information from
manufacturers and suppliers of artificial optical radiation sources
and products to ensure that they can undertake the assessments
required by the Directive. Ìt is suggested that the availability of such
information could form the basis for procurement policy.
4.2 ArticIe 5 - Provisions aimed at avoiding or reducing risks
Ìt is important to recognise that, unlike many other hazards, reducing the level of
artificial optical radiation below a certain level may actually increase the risk of injury.
An obvious example of this is area lighting. Ìndicator lamps and signals need to emit an
appropriate level of optical radiation to be fit for purpose. Therefore, Article 5
concentrates on avoiding or reducing risk. The approach used is similar to Directive
89/391/EEC and these principles are discussed further in Chapter 9 of this Guide.
4.3 ArticIe 6 - Worker information and training
The requirements of Article 6 are similar to those in Directive 89/391/EEC. Ìt is
important that the risks are put in perspective. Workers should be aware that many of
the sources of artificial optical radiation in the workplace do not present a risk to their
health and indeed many will contribute to their welfare. However, where risks have
been identified then appropriate information and training should be provided. This is
discussed further in Chapter 9.
4.4 ArticIe 7 - ConsuItation and participation of workers
This article refers to the requirements in accordance with Directive 89/391/EEC.
4.5 ArticIe 8 - HeaIth surveiIIance
Article 8 builds on the requirements of Directive 89/391/EEC. Many of the specific
details are likely to depend on systems in place in Member States. Some guidance on
health surveillance is provided in Chapter 11 of this Guide.
Many of the requirements of the Directive are already covered in other Directives,
particularly Directive 89/391/EEC (See Appendix E). Specific guidance on how to
comply with the Articles of the Directive is provided in Chapters of this Guide.
5 USE OF EXPOSURE LIMITS
Annexes Ì and ÌÌ of the Directive provide Exposure Limit Values (ELVs) for non-
coherent optical radiation and laser radiation, respectively. These ELVs take account
of the biological effectiveness of the optical radiation at causing harm at different
wavelengths, the duration of exposure to the optical radiation and the target tissue. The
ELVs are based on the Guidelines published by the Ìnternational Commission on Non-
Ìonizing Radiation Protection (ÌCNÌRP). Further information on the rationale for the
ELVs can be found in the Guidelines, which are available from www.icnirp.org (see
References). Ìt is worth noting that these Guidelines may be altered by ÌCNÌRP: should
this happen, the ELVs in the Directive may subsequently be modified.
Similar, but not identical, exposure limits have also been published by the American
Conference of Governmental Ìndustrial Hygienists (ACGÌH).
Ìt is necessary to know the wavelength range of the optical radiation before the correct
ELV can be selected. Ìt should be noted that more than one ELV may apply for a given
wavelength range. The ELVs for laser radiation are generally simpler to determine
because the emission is at a single wavelength. However, for laser products that emit
laser radiation at more than one wavelength, or for exposure scenarios involving
multiple sources, it may be necessary to take account of additive effects.
Full analyses of worker exposure and comparison with the ELVs can be complex and
beyond the scope of this Guide. The information presented below is intended to
provide guidance to employers on whether to seek further assistance.
5.1 Laser ELVs
The laser classification scheme (see Chapter 8.1.1) provides guidance to users on the
magnitude of the laser beam hazard ÷ as assessed under specific measurement
conditions. Class 1 laser products should be safe for normal use and therefore should
require no further assessment. However, an assessment will be required when a Class
1 laser product is maintained or serviced if this product contains an embedded laser of
a higher class. Unless information is supplied to the contrary, employers should
assume that laser beams from Class 3B and Class 4 lasers present a risk of eye injury.
Class 4 lasers also present a risk of skin injury.
A competent person, such as a Laser Safety Officer should be appointed where Class
3B and Class 4 lasers are used.
The assignment of a laser product to Class 2 is on the basis of the ELV not being
exceeded for an accidental exposure of up to 0.25 s. Ìf the use of the product means
that the eyes of workers are likely to be repeatedly exposed to the laser beam, then a
more detailed assessment should be carried out to determine if the ELV is likely to be
USE OF EXPOSURE LÌMÌTS
Class 1M, Class 2M and Class 3R lasers should be assessed to determine likely
exposure scenarios.
The ELVs for laser radiation are presented in Annex ÌÌ of the Directive, which is
reproduced in Appendix K of this Guide. The ELVs are expressed in terms of irradiance
(watts per square metre, W m
) or radiant exposure (joules per square metre, J m
The irradiance or radiant exposure from a laser beam should be averaged over an
aperture, called the limiting aperture, as specified in Tables 2.2, 2.3 and 2.4 of Annex ÌÌ
of the Directive, when calculating the irradiance or radiant exposure.
To find the correct laser ELV table:
Eye exposure ÷ short duration (<10 s) ÷ Table 2.2
Eye exposure ÷ 10 s or longer ÷ Table 2.3
Skin exposure ÷ Table 2.4
When deciding on the time of exposure, it will depend on whether the exposure is
accidental or intended. For accidental exposures, 0.25 s is generally assumed for laser
beams from 400 to 700 nm and 10 or 100 s for all other wavelengths, where the eye is
the exposed organ. Ìf only the skin is exposed, then it would be reasonable to use 10
or 100 s for all wavelengths.
Ìt is possible to calculate the maximum power through the stated aperture, for these
exposure durations, before the ELV is exceeded. The results of such calculations are
presented below for eye exposure to a continuous wave laser beam with a small
ELV (W m
) Maximum
aperture (mW)
180 to 302,5 1 10 3,0 0,000 002 4 0,002 4
302,5 to 315 1 10 3,16 to 1 000 0,000 002 5 to
0,000 79
0,002 5 to 0,79
305 1 10 10 0,000 007 9 0,007 9
308 1 10 39,8 0,000 031 0,031
310 1 10 100 0,000 079 0,079
312 1 10 251 0,000 20 0,20
315 to 400 1 10 1 000 0,000 79 0,79
400 to 450 7 0.25 25,4 0,000 98 0,98
450 to 500 7 0.25 25,4 0,000 98 0,98
500 to 700 7 0.25 25,4 0,000 98 0,98
700 to 1050 7 10 10 to 50 0,000 39 to
0,001 9
0,39 to 1,9
750 7 10 12,5 0,000 49 0,49
800 7 10 15,8 0,000 61 0,61
850 7 10 19,9 0,000 77 0,77
900 7 10 25,1 0,000 97 0,97
950 7 10 31,6 0,001 2 1,2
1000 7 10 39,8 0,001 5 1,5
1050 to 1400 7 10 50 to 400 0,001 9 to
1,9 to 15
1050 to 1150 7 10 50 0,001 9 1,9
1170 7 10 114 0,004 4 4,4
1190 7 10 262 0,010 10
1200 to 1400 7 10 400 0,015 15
1400 to 1500 3.5 10 1 000 0,009 6 9,6
1500 to 1800 3.5 10 1 000 0,009 6 9,6
1800 to 2600 3.5 10 1 000 0,009 6 9,6
2600 to 10
3.5 10 1 000 0,009 6 9,6
11 10 1 000 0,095 95
Further guidance on the assessment of ELVs is available in ÌEC TR 60825-14. Ìt
should be noted that the document uses the term maximum permissible exposure
(MPE) instead of ELV.
5.2 Non-Coherent OpticaI Radiation
The use of the ELVs for non-coherent optical radiation is generally more complex than
for laser radiation. This is due to worker exposure potentially being to a range of
wavelengths instead of a single wavelength. However, it is possible to make a number
of simplifying, worst-case, assumptions to determine if a more detailed assessment is
Three dimensionless modifying factors are provided in Tables 1.2 and 1.3 of Annex Ì to
the Directive. The weighting function S( ) applies from 180 to 400 nm and is used to
modify spectral irradiance or spectral radiant exposure data to take account of the
wavelength dependency of adverse health effects on the eye and the skin. When a
weighting function has been applied, the subsequent data are usually referred by terms
such as effective irradiance or effective radiant exposure.
Figure 5.1 - Weighting function S( )
The peak value for S( ) is 1.0 at 270 nm. A simple approach is to assume that all of the
emission between 180 nm and 400 nm is at 270 nm (since the S( ) function has a
maximum value of 1, this is equivalent to simply ignoring the function altogether).
Since the ELV is expressed in terms of radiant exposure (J m
), if the irradiance of the
source is known it is possible to use the table below to see the maximum time a worker
can be exposed if they are not to exceed the ELV, which is set at 30 J m
Ìf this time is not exceeded by assuming all of the emission is at 270 nm then no further
assessment is required. Ìf the ELV is exceeded then a more detailed spectral
assessment is required.
180 230 280 330 380
WaveIength (nm)
Duration of exposure per 8 hour day Irradiance (Effective) - W m
8 hours 0,001
4 hours 0,002
2 hours 0,004
1 hour 0,008
30 minutes 0,017
15 minutes 0,033
10 minutes 0,05
5 minutes 0,1
1 minute 0,5
30 seconds 1,0
10 seconds 3,0
1 second 30
0,5 second 60
0,1 second 300
The factor B( ) is applied between 300 nm and 700 nm to take account of the
wavelength dependence of the photochemical injury risk to the eye. The wavelength
dependence is plotted below.
300 350 400 450 500 550 600 650 700
Figure 5.2 - Weighting function B( )
The peak weighting factor is 1.0 between 435 and 440 nm. Ìf the ELV is not exceeded
by assuming that all of the emission between 300 nm and 700 nm is at about 440 nm
(since the B( ) function has a maximum value of 1, this is equivalent to simply ignoring
the function altogether), then it will not be exceeded when a more detailed assessment
is carried out.
The weighting factor R( ) is defined between 380 and 1400 nm and is plotted below.
RÌSK ASSESSMENT ÌN THE CONTEXT OF THE DÌRECTÌVE
380 580 780 980 1180 1380
waveIength, nm
Figure 5.3 - Weighting function R( )
The peak of R( ) is between 435 and 440 nm. Ìf the ELV is not exceeded by assuming
that all of the emission between 380 nm and 1400 nm is at about 440 nm (since the
R( ) function has a maximum value of 10, this is equivalent to simply multiplying all of
the unweighted values by 10), then it will not be exceeded when a more detailed
assessment is carried out.
Table 1.1 of Annex Ì of the Directive provides the ELVs for different wavelengths. Ìn
some wavelength regions, more than one exposure limit will apply. None of the
relevant exposure limits should be exceeded.
Guidelines on Limits of Exposure to Ultraviolet Radiation of Wavelengths Between 180
nm and 400 nm (Ìncoherent Optical Radiation). Health Physics 87 (2): 171-186; 2004.
Revision of the Guidelines on Limits of Exposure to Laser radiation of wavelengths
between 400nm and 1.4µm. Health Physics 79 (4): 431-440; 2000.
Guidelines on Limits of Exposure to Broad-Band Ìncoherent Optical Radiation (0.38 to
3µm). Health Physics 73 (3): 539-554; 1997.
Guidelines on UV Radiation Exposure Limits. Health Physics 71 (6): 978; 1996.
Guidelines on Limits of Exposure to Laser Radiation of Wavelengths between 180 nm
and 1 mm. Health Physics 71 (5): 804-819; 1996.
6 RISK ASSESSMENT IN THE CONTEXT OF THE DIRECTIVE
Risk assessment is a general requirement of Directive 89/391/EEC. The approach
presented here is based on the European Agency for Safety and Health at Work
stepwise approach to risk assessment:
A stepwise approach to risk assessment
Step 1. Ìdentifying hazards and those at risk
Step 2. Evaluating and prioritising risks
Step 3. Deciding on preventive action
Step 5. Monitoring and reviewing
A full risk assessment will need to consider all of the hazards associated with the work
activity. However, for the purposes of the Directive, only the optical radiation hazard
will be addressed here. For some applications, adequate information will be supplied
by the product manufacturer to conclude that the risk is adequately managed.
Therefore, the risk assessment process need not be particularly onerous. Unless
National legislation requires it, the risk assessment need not be written down for trivial
sources. However, employers may decide to make a record to demonstrate that an
assessment has been carried out.
6.1 Step 1. Identifying hazards and those at risk
All optical radiation sources should be
identified. Some sources will already be
contained within equipment such that
worker exposure is not possible during
normal use. However, it will be necessary
to consider how workers may get exposed
throughout the life of the source. Ìf workers
manufacture optical radiation products
then they may be at greater risk than
users. The typical life cycle of an optical
radiation product is as follows:
Product Life CycIe
Ìnstallation
Exposure to optical radiation usually occurs when the product is operating. 1 to 3 may
take place on another employer's premises. 4 to 10 usually occur at the normal place
of work. Ìt should also be noted that some parts of the Life Cycle are indeed cyclic. For
example, an item of work equipment may need routine maintenance every week:
servicing may take place every six months. A degree of commissioning may be
required after each service operation. At other times, the item of work equipment is at
the "normal operation¨ stage.
The employer should consider which groups of employees or contractors are likely to
be exposed to optical radiation at each part of the Life Cycle.
Record all of the likely sources of exposure to artificial optical radiation and
consider who may be exposed.
6.2 Step 2. EvaIuating and prioritising risks
The Directive requires exposures of workers to optical radiation to be below the
exposure limit values contained in Annexes Ì and ÌÌ of the Directive. Many sources of
optical radiation in the workplace will be trivial. Appendix D of this Guide provides
guidance for some specific applications. The judgement on whether a source is trivial
will also need to take into account how many sources the worker is likely to be
exposed to. For a single source, if the exposure at the location of the worker is less
than 20 % of the ELV for a full working day, then it might be considered trivial.
However, if there are 10 such sources, then the exposure from each source would
need to be less than 2 % of the ELV to be considered trivial.
Ìt is important to stress that the Directive requires "risks¨ to be eliminated or reduced to
a minimum. This doesn't necessarily mean that the amount of optical radiation should
be reduced to a minimum. Clearly, turning all of the lights out will compromise safety
and increase the risk of injury.
An approach to evaluating the risk is as follows:
1. Decide which sources are "trivial¨. Consideration should be given to making a record
of this decision
2. Decide which exposure scenarios need further assessment
3. Assess the exposure against the exposure limit value
4. Consider exposure to multiple sources
5. Ìf the exposure limit value is likely to be exceeded, take action (See Steps 3 and 4)
6. Record the significant conclusions
Determining the risk of exposure, i.e. how likely the exposure is, may not be
straightforward. A well-collimated laser beam can be present in the workplace and the
risk of exposure to the laser beam may be small. However, the consequences, should
an exposure take place, may be great. Ìn contrast, the risk of exposure to the optical
radiation from many non-coherent artificial sources may be high, but the consequences
could be low.
For most workplaces, the requirement to quantify the risk of exposure is not justified,
beyond assigning a "common sense¨ high, medium or low probability.
The Directive does not define the term "likely¨ in the context of "likely to be
exposed¨. Therefore, unless National requirements suggest otherwise,
common sense is adequate
Consider making a record of trivial sources
Record sources where a risk of exceeding the exposure limit value exists
Make a judgement on the risk
Consider any workers who may be particularly photosensitive
Prioritise control measures for sources likely to expose workers above the exposure
Although the exposure limit values for ultraviolet radiation can be used to determine the
maximum irradiance that a worker can receive over a working day, such repeated
exposures for every working day are not ideal. Consideration should be given to
reducing ultraviolet radiation exposures to values as low as reasonably practicable,
rather than working up to the exposure limit value.
6.3 Step 3. Deciding on preventive action
Chapter 9 of this Guide provides guidance on the control measures that may be used
to minimise the risk of exposure to artificial optical radiation. Collective protection is
generally preferred to personal protection.
Decide on the appropriate preventive action
Record the justification for the decision
6.4 Step 4. Taking action
Ìt is necessary to implement the preventive action. A judgement on the risk from the
exposure to the artificial optical radiation will determine whether the work may proceed
with caution until the preventive measures are in place, or whether the work should
stop until they are in place.
Decide whether work can continue
Ìmplement preventive action
Ìnform workers of the basis for the preventive action
MEASUREMENT OF OPTÌCAL RADÌATÌON
6.5 Step 5. Monitoring and reviewing
Ìt is important to determine if the risk assessment was effective and the preventive
measures are adequate. Ìt is also necessary to review the risk assessment if artificial
optical radiation sources change, or work practices are modified.
Workers may not necessarily know that they are photosensitive, or they may develop
photosensitivity after the risk assessment has been completed. All claims should be
recorded and, where appropriate, health surveillance used (see Chapter 11 of this
Guide). Ìt may be necessary to change the source(s) of artificial optical radiation or
otherwise adjust work practices.
Decide on an appropriate routine review interval ÷ perhaps 12 months
Ensure that reviews are carried out if the situation changes, such as new
sources are introduced, work practices change, or adverse incidents occur
Record the reviews and the conclusions
European Agency for Safety and Health at Work:
http://osha.europa.eu/en/topics/riskassessment.
7 MEASUREMENT OF OPTICAL RADIATION
7.1 Requirements under the Directive
The measurement of optical radiation is something that may be done as part of the risk
assessment process. The Directive sets out its requirements for risk assessments in
Article 4. Ìt is stated that:
"...the employer, in the case of workers exposed to artificial sources of optical radiation,
shall assess, and, if necessary, measure and/or calculate the levels of exposure to
optical radiation to which workers are likely to be exposed...¨
This statement allows the employer to determine the worker's exposure levels by
means other than measurement, i.e. by calculation (using data supplied by a third
party, such as the manufacturer).
Ìf it is possible to acquire data which are adequate for the purposes of risk assessment,
then measurement is not necessary. This is a desirable situation: workplace
measurement of optical radiation is a complex task. The measurement equipment is
likely to be relatively expensive and can only be used successfully by a competent
person. An inexperienced operator can easily make mistakes which will lead to highly
inaccurate data being produced. Ìt will also often be necessary to assemble time and
motion data for the workplace tasks which are the subject of the risk assessment.
7.2 Seeking further assistance
Unless the employer is willing to purchase, and has the expertise to use, optical
radiation measurement equipment, then assistance will be required. The requisite
measurement equipment might be found (together with the expertise to use it) in:
national health and safety establishments
research establishments (such as universities with an optics department)
manufacturers of optical measurement equipment (and possibly their agents)
specialist private health and safety consultancies
When approaching any of these potential sources of assistance, it is worth bearing in
mind that they should be able to demonstrate:
knowledge of the exposure limits and their application
equipment which can measure all of the wavelength regions of interest
experience in the use of the equipment
a method of calibrating the equipment traceably to some nationally maintained
the ability to estimate the uncertainty on any measurements that are made
Unless all of these criteria can be satisfied, it is possible that the resulting risk
assessment could be defective due to:
failure to apply the correct limits, or failure to apply them correctly
failure to acquire data which can be compared to all of the applicable limits
gross errors in the numerical values of the data
data which cannot be compared with the appropriate limits to give an
unequivocal conclusion
8 USE OF MANUFACTURERS' DATA
Because of the wide variety of sources emitting optical radiation, the risks arising in
their use vary considerably. Data provided by manufacturers of equipment emitting
optical radiation should assist users in hazard evaluation and determination of required
control measures. Ìn particular, safety classification of laser and non-laser sources and
hazard distances could be very useful for carrying out the risk assessment.
USE OF MANUFACTURERS' DATA
8.1 Safety cIassification.
The classification schemes for lasers and non-laser sources indicate the potential risk
of adverse health effects. Depending upon conditions of use, exposure time or
environment, these risks may or may not actually lead to adverse health effects. With
the help of classification, users may select appropriate control measures to minimise
these risks.
8.1.1 Laser safety cIassification.
The classification of lasers is based on the concept of accessible emission limit (AEL);
these are defined for each laser class. AEL takes into account not only the output of
the laser product but human access to the laser emission. Lasers are grouped into 7
Classes: the higher the Class, the bigger the potential to cause harm. The risk could
be greatly reduced by additional user protective measures, including additional
engineering controls such as enclosures.
Useful to remember
'M' in Class 1M and Class 2M is derived from Magnifying optical viewing
'R' in Class 3R is derived from Reduced, or Relaxed, requirements: reduced
requirements both for the manufacturer (e.g. no key switch, beam stop or
attenuator and interlock connector required) and the user
The 'B' for Class 3B has historical origins
8.1.1.1 Class 1
Laser products that are considered safe during
use, including long-term direct intrabeam viewing,
even when using optical viewing instruments (eye
loupes or binoculars). Users of Class 1 laser
products are generally exempt from optical
radiation hazard controls during normal operation.
During user maintenance or service, higher level
of radiation might become accessible.
1 1M 2 2M 3R 3B 4 1 1M 2 2M 3R 3B 4
Laser CIass
This class includes products that contain high-power lasers within an enclosure that
prevents human exposure to the radiation and that cannot be opened without shutting
down the laser, or require tools to gain access to the laser beam:
CD and DVD players and recorders
Materials processing lasers
8.1.1.2 Class 1M
Safe for the naked eye under reasonably
foreseeable conditions of operation, but may
be hazardous if the user employs optics (e.g.
loupes or telescopes) within the beam
Example: a disconnected fibre optic communication systems
Ìntra-beam viewing of visible Class 1 and 1M laser products may still cause
dazzle, particularly in low ambient light
8.1.1.3 Class 2
Laser products that emit visible radiation and are safe
for momentary exposures, even when using optical
viewing instruments, but can be hazardous for
deliberate staring into the beam. Class 2 laser products
are not inherently safe for the eyes, but protection is
assumed to be adequate by natural aversion responses,
including head movement and the blink reflex
Examples: bar-code scanners
8.1.1.4 Class 2M
Laser products that emit visible laser beams
and are safe for short time exposure only for the
naked eye; possible eye injury for exposures
when using loupes or telescopes. Eye
protection is normally provided by aversion
responses including the blink reflex
Examples: level and alignment instruments for civil engineering applications
8.1.1.5 Class 3R
Direct intra-beam viewing is potentially hazardous but
practically the risk of injury in most cases is relatively
low for short and unintentional exposure; however, may
be dangerous for improper use by untrained persons.
The risk is limited because of natural aversion
behaviour for exposure to bright light for the case of
visible radiation and by the response to heating of the
cornea for far infrared radiation.
Class 3R lasers should only be used where direct intra-beam viewing is unlikely.
Examples: surveying equipment, higher power laser pointers, alignment lasers
Aversion response doesn't happen universally
Viewing of Class 2, 2M or visible-beam 3R laser products may cause
dazzle, flash-blindness and afterimages, particularly in low ambient light.
This may have indirect general safety implications resulting from temporary
disturbance of vision or from startle reactions. Visual disturbances could be
of particular concern when performing safety-critical operations such as
working with machines or at height, with high voltages or driving.
8.1.1.6 Class 3B
Hazardous for the eyes if exposed to the direct beam within the nominal ocular hazard
distance (NOHD ÷ see 8.4.1). Viewing diffuse reflections is normally safe, provided the
eye is no closer than 13 cm from the diffusing surface and the exposure duration is
less than 10 s. Class 3B lasers which approach the upper limit for the class may
produce minor skin injuries or even pose a risk of igniting flammable materials.
Examples: lasers for physiotherapy treatments; research laboratory equipment
8.1.1.7 Class 4
Laser products for which direct viewing and skin
exposure is hazardous within the hazard
distance and for which the viewing of diffuse
reflections may be hazardous. These lasers also
often represent a fire hazard
Examples: laser projection displays, laser surgery and laser metal cutting
Class 3B and Class 4 laser products should not be used without first carrying
out a risk assessment to determine the protective control measures necessary
to ensure safe operation
TabIe 8.1. Summary of required controIs for different Iaser safety cIasses
CIass 1 CIass 1M CIass 2 CIass 2M CIass 3R CIass 3B CIass 4
of hazard
Safe under
Safe for naked
eye;, may be
hazardous if
employs optics
exposures;
protection is
afforded by
eye for short
exposures,;
low, but may
for improper
Direct viewing
for eye and
skin; fire
ControIIed
Localised or
Not required Localised or
enclosed Enclosed and
Enclosed and
Key controI
Not required Not required Not required Not required required required
r instruction
for safe use
Recommended Follow
Recommended Required Required Required
Not required Not required Not required May be
required ÷
findings of the
Prevent use of
focusing or
into the beam.
Prevent direct
Prevent eye
the beam.
and diffuse
Limitations of the laser classification scheme
Laser safety classification relates to accessible laser radiation ÷ this classification doesn't take
into account additional hazards, such as electricity, collateral radiation, fume, noise, etc
Laser safety classification relates to normal use of the product ÷ it might not be applicable to
maintenance or service, or when the original device forms a part of a complex installation
Laser safety classification relates to a single product ÷ it doesn't account for accumulative
exposure from multiple sources
8.1.2 Safety cIassification of non-coherent sources
The safety classification of non-coherent (broad-band) sources is defined in EN 62471:
2008 and is based on the maximum accessible emission over the full range of
capability of the product during operation at any time after manufacture. Classification
takes account of the quantity of optical radiation, the wavelength distribution and
human access to optical radiation. Broad-band sources are grouped into 4 Risk
Groups: the higher the Risk Group, the bigger potential to cause harm.
The classification indicates the potential risk of adverse health effects. Depending upon
conditions of use, exposure time or environment, these risks may or may not actually
lead to adverse health effects. With the help of classification, the user may select
appropriate control measures to minimise these risks.
Ìn increasing order of risk, the following ranking of the Risk Groups is used:
Exempt Group - no photobiological hazard under foreseeable conditions;
Risk Group 1 - Low risk group, the risk is limited by normal behavioural
limitations on exposure;
Risk Group 2 - Moderate risk group, the risk is limited by the aversion response
to very bright light sources. However, such reflex responses do not occur
universally;
Risk Group 3 - High risk group, may pose a risk even for momentary or brief
Within each risk group, different time criteria have been set for each hazard. These
criteria have been chosen so that the applicable ELV will not be exceeded within the
chosen time.
8.1.2.1 Exempt Group
No direct optical radiation risks are reasonably foreseeable, even for continuous,
unrestricted use. These sources do not pose any of following photo-biological hazards:
an actinic ultraviolet hazard within 8-hours
a near-UV hazard within 1000 s;
a retinal blue-light hazard within 10000 s;
a retinal thermal hazard within 10 s;
an infrared radiation hazard for the eye
within 1000 s;
an infrared radiation hazard without a strong
visual stimulus within 1000 s
Examples: domestic and office lighting, computer monitors, equipment displays,
indicator lamps.
8.1.2.2 Risk Group 1 ÷ Low risk
These products are safe for most applications, except for very prolonged exposures
where direct ocular exposures may be expected. These sources do not pose any of
following hazards due to normal behavioural limitations on exposure:
Risk Group of broad-band
Exempt Risk Group 1 Risk Group 2 Risk Group 3
an actinic ultraviolet hazard within 10000 s;
a near-UV hazard within 300 s;
a retinal blue-light hazard within 100 s;
an infrared radiation hazard for the eye within 100 s
an infrared radiation hazard without a strong visual
stimulus within 100 s
Example: domestic torch
8.1.2.3 Risk Group 2 ÷ Moderate risk
The sources that do not pose any of following hazards due to aversion response to
very bright light sources, due to thermal discomfort or where lengthy exposures are
an actinic ultraviolet hazard within 1000 s;
a near-UV hazard within 100 s;
a retinal blue-light hazard within 0.25 s (aversion response);
a retinal thermal hazard within 0.25 s (aversion response);
an infrared radiation hazard for the eye within 10 s
an infrared radiation hazard without a strong visual stimulus within 10 s
8.1.2.4 Risk Group 3 ÷ High risk
The sources that may pose a risk even for momentary or brief exposure within hazard
distance. Safety control measures are essential.
Filtering of unwanted excessive optical radiation (e.g. UV), shielding the
source to prevent access to optical radiation or employing beam
expanding optics may lower a Risk Group and decrease the risk from
Limitations of the broad-band sources classification scheme
Safety classification relates to accessible optical radiation ÷ this classification doesn't
take into account additional hazards, such as electricity, collateral radiation, fume,
noise, etc
Safety classification relates to normal use of the product ÷ it might not be applicable to
maintenance or service, or when the original device forms a part of a complex
Safety classification relates to a single product ÷ it doesn't account for accumulative
Products are classified at a distance which produces an illuminance of 500 lx for
General Lighting Systems (GLS) and at 200 mm from the source for other applications
÷ it may not be representative for all use conditions
8.1.3 Safety cIassification of machinery
Machinery which produces optical radiation may be also classified to EN 12198. This
standard applies to all emissions, either intentional or adventitious, apart from sources
used purely for illumination.
Machinery is classified into one of three categories, depending on the accessible
emission. The three categories, in increasing order of risk, are listed in Table 8.2.
TabIe 8.2 Safety cIassification of machinery according to EN 12198
Category Restrictions and protective
No restriction No information needed
Restrictions: limitation of access,
protective measures may be needed.
Ìnformation about hazards, risks and secondary
effects to be provided by manufacturer.
Special restrictions and protective
measures essential.
effects to be provided by manufacturer. Training may
Assignment of a machine to one of these categories is based on the effective
radiometric quantities presented below in Table 8.3, as measured at a distance of 10
TabIe 8.3. Emission Iimits for machinery cIassification according to EN 12198
(for < 11 mrad) (for 11 mrad)
0.1 mW m
1 mW m
10 W m
33 W m
1.0 mW m
10 mW m
100 W m
> 1.0 mW m
> 10 mW m
> 100 W m
8.2 Hazard distance and hazard vaIues information
Ìn some applications it can be useful to know the distance over which the hazards from
optical radiation might extend.
The distance at which the level of exposure has dropped to the level of the applicable
Exposure Limit Value is known as the hazard distance: beyond this distance there is
no risk of harm. This information, if provided by manufacturers, may be useful for the
risk assessment and for ensuring a safe work environment.
8.2.1 Lasers - NominaI OcuIar Hazard Distance
At some distance, as the laser beam diverges, the irradiance will equal the ELV for
eyes. This distance is called the Nominal Ocular Hazard Distance (NOHD). At greater
distances the ELV will not be exceeded ÷ the laser beam is considered safe beyond
Manufacturers often provide the information on NOHD with product specification. Ìf this
information is not available, it is possible to calculate the NOHD using the following
parameters for the laser radiation from manufacturer data:
Radiant power (W)
Ìnitial beam diameter (m)
Divergence (radians)
Exposure Limit Value (ELV) (W m
Although the situation may be complicated if the distance is large or if the beam is not
circular, the following equation gives a good estimate of the NOHD:
8.2.2 Broad-band sources - Hazard Distance and Hazard VaIue
Exposure Limit Value is known as the Hazard Distance (HD): beyond this distance
there is no risk of harm. The HD should be taken into account when specifying the
boundaries of the area within which access to optical radiation and the activity of
personnel is subject to control and supervision for the purpose of protection from
optical radiation. Hazard distances may be defined for eye or skin exposure.
Optical radiation hazards information could also be presented as Hazard Value (HV),
which is the ratio of the Exposure Level at a specific distance to the Exposure Limit
Value at that distance:
Value Limit Exposure
time) exposure (distance, Level Exposure
time) exposure e, HV(distanc
The Hazard Value, HV, has significant practical importance. Ìf the HV is greater than 1,
it gives guidance on appropriate control measures: either to limit the exposure duration
or the accessibility of a source (attenuation, distance), as applicable. Ìf the HV is less
than one, the ELV is not exceeded at that location for the exposure time considered.
Manufacturers often provide information on HD and Hazard Values with the product
specification. This information should assist the user in undertaking the risk
assessment and the choice of appropriate control measures.
8.3 Further usefuI information
EN 60825-1: 2007. Safety of Laser Products. Part 1: Equipment Classification and
ÌEC TR 60825-14: 2004. Safety of Laser Products. Part 14: A user's guide
EN 62471: 2008, Photobiological safety of lamps and lamp systems
EN 12198 ÷ 1: 2000. Safety of Machinery ÷ Assessment and reduction of risks from
radiation Emitted by machinery. Part 1: General Principles.
ameter initial di -
x ELJ
power x radiant
NOHD ÷
EN 12198 ÷ 2: 2002. Safety of Machinery ÷ Assessment and reduction of risks from
radiation Emitted by machinery. Part 2: Radiation Emission Measurement Procedure
EN 12198 ÷ 3: 2000. Safety of Machinery ÷ Assessment and reduction of risks from
radiation Emitted by machinery. Part 3: Reduction of Radiation by Attenuation and
9 CONTROL MEASURES
The hierarchy of control measures is based on the principle that if any hazard is
identified, then this hazard must be controlled by engineering design. Only when this is
not possible, should alternative protection be introduced. There are very few
circumstances where it is necessary to rely on personal protective equipment and
The selection of appropriate measures in any specific situation should be guided by the
outcome of the risk assessment. All available information about the sources of optical
radiation and the possible personal exposure should be gathered. Ìn general, a
comparison of either the radiation exposure obtained from the equipment specifications
or measured data together with the applicable Exposure Limit Value(s) allows an
assessment of a personal workplace exposure to optical radiation. The aim is to get an
unambiguous result stating whether the applicable limit value(s) is likely to be
exceeded or not.
Ìf a clear statement can be made that optical radiation exposure is insignificant and
that the exposure limit values will not be exceeded, no further action is necessary.
Ìf emissions are significant and/or occupancy is high, it may be possible that the limits
will be exceeded and that some form of protective measures will be required. The
assessment procedure should be repeated after the application of protective
Repetition of the measurement and assessment may be necessary if:
the radiation source has changed (e.g. if another source has been installed or if the
source is operated under different operating conditions);
the nature of the work has changed;
the duration of exposure has changed;
protective measures have been applied, discontinued or changed;
a long period of time has elapsed since the last measurement and assessment so
that the results may no longer be valid;
a different set of exposure limit values is to be applied.
Control measures applied at the design and installation stage can offer significant
advantages in safety and operation. The later addition of such control measures may
9.1 Hierarchy of controI measures
Where there is a potential for exposure above the ELV, the hazard should be managed
through application of a combination of appropriate control measures. The control
priorities are common for risk management:
Substitution by less hazardous process or
9.2 EIimination of the hazard
Ìs the source of hazardous optical radiation really necessary?
Do you really need these lights ON?
9.3 Substitution by Iess hazardous process or equipment
Ìs the hazardous level of optical radiation essential?
Do you really need it so bright?
9.4 Engineering controIs
Could the equipment be re-designed or hazardous optical radiation controlled or
reduced at the source?
Ìf the higher priority controls (elimination or substitution) are not possible, preference
should be given to engineering means of reduction of exposure. Administrative controls
may be used in combination with higher control measures. Ìf reduction of personal
exposure is not feasible, impracticable or incomplete, personal protective equipment
(PPE) should be considered as a last resort.
9.4.1 Access Prevention
This can be undertaken either with fixed guards or movable guards with interlocks.
Fixed guards are usually applied to parts of the equipment which do not require regular
access and are permanently attached.
Ìf access is needed, then a movable/opening guard interlocked to the process can be
Guards should be adequate and robust
Should not generate any additional risks and should cause minimal
Should not be easy to be bypassed or defeated ÷ if it is a fixed enclosing
Should be located at an adequate distance from the danger zone ÷ if it's a
fixed distance guard
Ìnterlocks
Delayed operation switches
Attenuators Shutters
Viewing and filtered windows
Elimination of reflections
Preventing access to laser beam
9.4.2 Protection by Limiting Operation
When frequent access is required through the physical guards, then these can often be
considered too restrictive, especially if the operator is required to carry out
loading/unloading or adjustment operations. Ìn this instance, it is usual to employ
sensors to detect the presence or absence of an operator and generate an appropriate
stop command. They can be classed as trip devices: they do not restrict access but
sense it. The time taken for the machine to reach a safe condition determines the
location or proximity of any sensor.
9.4.3 Emergency Stops
When personnel can access a hazardous environment, it is essential to provide
emergency stops should anyone get into trouble while in the hazard zone. The
emergency stop must have a fast response and stop all services in the hazard zone.
Most people will be familiar with the red mushroom headed emergency stop buttons;
they should be suitably located around the facility in sufficient quantity to ensure there
will always be one in reach. An alternative is a grab wire linked to an emergency stop
button, this is often a more convenient means of providing protection in a hazard area.
Other forms of trip switch can be located around any moving parts which sense
unexpected proximity such as a toggle switch, safety bar or rod.
9.4.4 InterIocks
There are many variations of interlock switches and each design comes with its own
features. Ìt is important that the right device be chosen for the application.
Ìnterlock should be well constructed and reliable under the foreseeable
They should fail-to-safety and be tamper proof
The status of the interlock should be clearly indicated, e.g by large flags on
the defeat keys and warning status indicators on operators panels
The interlock should limit the operation whilst the guard door is not fully
Further usefuI information
EN 953: 1997 The Safety of Machinery, Guards, General requirements for the
Design and Construction of Fixed and Moveable Guards.
EN 13857: 2008 Safety of Machinery, safety distances to prevent danger zones
being reached by upper and lower limbs.
EN 349: 1993 Safety of Machinery, minimum gaps to avoid crushing of parts of the
EN 1088: 1995 Ìnterlocking Devices Associated with Guards
EN 60825-4: 2006 Laser Guards
9.4.5 FiIters and Viewing Windows
Many industrial processes can be fully or partially enclosed. Ìt is then possible to
monitor the process remotely, via a suitable viewing window, optics or television
camera. Safety can be ensured by using appropriate filter materials to block the
transmission of hazardous levels of optical radiation. This removes any need for
reliance upon safety goggles and improves operator safety and working conditions.
Examples can range from large scale control rooms to a viewing window fitted within a
small local enclosure around the interaction region.
Filter material should be durable and appropriate
Ìmpact resistant
Doesn't compromise safety of operation
Vision panels in guarded area
Transmission of optical radiation through windows and other optically translucent
panels should be evaluated as a potential risk. Although the optical beam may not
present a direct retinal hazard, temporary flash issues may cause secondary safety
problems with other procedures in the vicinity.
9.4.6 AIignment Aides
When routine maintenance requires the alignment of beam path components, some
safe means of achieving this should be provided. Some examples may include:
Use of a lower power sighting laser that follows the axis of the higher power beam,
Masks or targets.
The human eye or skin should never be used as an alignment aid
9.5 Administrative measures
Administrative Controls are the second stage of the hierarchy of control. They tend to
need people to act on information and, therefore, are only as effective as the actions of
those people. However, they do have a role and may be the principal control measure
under some circumstances, such as during commissioning and servicing.
The appropriate administrative controls depend on the risk and include the
appointment of people as part of the safety management structure, restricting access,
signs and labels, and procedures.
Ìt is good practice to provide formal arrangements for an integrated approach to the
management of optical radiation safety. These arrangements should be documented to
record what measures have been adopted and why. This documentation also may
prove useful in the event of an incident investigation. Ìt may include:
a statement of the optical radiation safety policy;
a summary of the principal organisational arrangements (appointments and what is
expected of the person appointed to each position);
a documented copy of the risk assessment;
an action plan detailing any additional controls identified through the risk
assessment together with a timetable for their implementation;
a summary of the control measures implemented together with a brief justification
a copy of any specific written arrangements or local rules applying to work in the
optical radiation controlled area;
the Authorised Users' Register;
plan for maintaining the control measures. This may include schedules for positive
actions required to maintain or test the control measures;
details of formal arrangements to manage interactions with external agents such as
service engineers;
details of contingency plans;
an audit plan;
copies of audit reports;
copies of relevant correspondence.
Ìt should be normal practice to review the effectiveness of the programme at regular
intervals (for example, annually) in the light of the audit reports and changes in
legislation and standards.
9.5.1 LocaI RuIes
Where the risk assessment identified a potential for exposure to hazardous level of
optical radiation, it is appropriate to put in place a system of written safety instructions
(or Local Rules) to regulate how work with optical radiation is carried out. These should
include a description of the area, contact details for an Optical Radiation advisor (see
9.5.4), details of who is authorised to use the equipment, details of any pre-use tests
required, operating instructions, an outline of the hazards, and details of contingency
Local Rules should normally be available in the areas to which they relate and should
be issued to all those affected by them.
9.5.2 ControIIed Area
A controlled area may need to be designated where access to optical radiation in
excess of the ELV is likely. A controlled area should be one to which access is
restricted, except to authorised persons. This should preferably be by physical means,
for example, using the walls and doors of the entire room. The area may be restricted
by locks, number pads, or barriers.
Arrangements should be put in place for the formal authorisation of users by
management. There should be a formal process for evaluating the suitability of
personnel prior to authorisation and this should include an assessment of their training,
competence and knowledge of the Local Rules. The results of this assessment should
be recorded and the names of all authorised users should be recorded in a formal
9.5.3 Safety signs and notices
These form an important part of any system of administrative controls. Safety signs are
only effective if they are clear and unambiguous, and if they are displayed only when
appropriate ÷ otherwise they are often ignored.
Warning signs may include information about the type of equipment in use. Ìf there is a
requirement for personnel to use personal protective equipment, then this should also
Warning signs are more effective if they are displayed only when the equipment is in
use. All safety signs should be placed at eye level to maximise their visibility.
Typical signs used in the work environment to advise of hazards and recommend the use of
All safety signs should comply with the requirements of Safety Signs Directive
(92/58/EEC).
EYEWEAR MUST BE
WORN WHEN LASER IS
9.5.4 Appointments
Optical radiation safety should be managed through the same health and safety
management structure as other potentially hazardous activities. The detail of the
organisational arrangements may vary according to the size and structure of the
For many applications, the training of an expert in optical radiation safety management
may not be justified. Ìt may also be difficult for staff to keep up to date with optical
radiation safety if they are only required to use their skills infrequently. Therefore, some
companies make use of advice provided by external advisers in optical radiation safety.
They may provide recommendations on:
engineering control solutions;
written procedures for the safe use of the equipment, operational and occupational
safety measures;
selection of personal protective equipment;
education and training of staff.
To supervise the day-to-day aspects of optical radiation safety in a workplace, it may
be appropriate to appoint a sufficiently knowledgeable member of staff.
9.5.5 Training and ConsuItation
9.5.5.1 Training
The Directive (Article 6) requires information and training for workers who are exposed
to risks from artificial optical radiation (and/or their representatives). This is required to
cover in particular:
Measures taken to implement this Directive
The exposure limit values and the associated potential risks
The results of the assessment, measurement and/or calculations of the
levels of exposure to artificial optical radiation carried out in accordance
with Article 4 of this Directive together with an explanation of their
significance and potential risks
How to detect adverse health effects of exposure and how to report them
The circumstances in which workers are entitled to health surveillance
Safe working practices to minimise risks from exposure
Proper use of appropriate personal protective equipment
Ìt is suggested that the level of training should be balanced with the risk from exposure
to artificial optical radiation. Where all of the sources are considered "trivial¨ then it
should be adequate to inform workers and/or their representatives of this. However,
workers or their representatives should be made aware that there could be particularly
sensitive risk groups and the process for managing these.
Where accessible artificial optical radiation that is likely to exceed the exposure limit
value is present in the workplace then consideration should be given to formal training,
and perhaps the appointment of workers to specific roles. When determining the level
of training required, the employer should consider the following:
Expertise of staff and current awareness of the risks from artificial optical radiation
Existing risk assessments and their conclusions
Whether the workers are required to assist with risk assessments or their review
Whether the workplace is static and the risks have been formally assessed as
acceptable or whether the environment changes frequently
Whether the employer has access to external expertise to assist with the
Workers new to the workplace or to work with artificial optical radiation
Ìt is important that the risks are put into perspective. For example, requiring formal
training courses for the use of a Class 2 laser pointer is not justified. Training for
workers using Class 3B and Class 4 lasers, and non-coherent sources of Risk Group
3, will almost always be required. However, it is not possible to define a specific length
of a training programme or indeed how this is to be delivered. This is why the risk
assessment is important.
Ìdeally, the requirement for training, and how this should be delivered, should be
identified before the source of artificial optical radiation is brought into use.
9.5.5.2 Consultation
Article 7 of the Directive refers to the general requirements of Article 11 of Directive
89/391/EEC:
ArticIe 11
ConsuItation and participation of workers
1. Employers shall consult workers and/or their representatives and allow them to take part in
discussions on all questions relating to safety and health at work.
This presupposes:
- the consultation of workers,
- the right of workers and/or their representatives to make proposals,
- balanced participation in accordance with national laws and/or practices.
2. Workers or workers' representatives with specific responsibility for the safety and health of
workers shall take part in a balanced way, in accordance with national laws and/or practices, or shall
be consulted in advance and in good time by the employer with regard to:
(a) any measure which may substantially affect safety and health;
(b) the designation of workers referred to in Articles 7 (1) and 8 (2) and the activities
referred to in Article 7 (1);
(c) the information referred to in Articles 9 (1) and 10;
(d) the enlistment, where appropriate, of the competent services or persons outside the
undertaking and/or establishment, as referred to in Article 7 (3);
(e) the planning and organization of the training referred to in Article 12.
3. Workers' representatives with specific responsibility for the safety and health of workers shall
have the right to ask the employer to take appropriate measures and to submit proposals to him to
that end to mitigate hazards for workers and/or to remove sources of danger.
4. The workers referred to in paragraph 2 and the workers' representatives referred to in paragraphs
2 and 3 may not be placed at a disadvantage because of their respective activities referred to in
paragraphs 2 and 3.
5. Employers must allow workers' representatives with specific responsibility for the safety and
health of workers adequate time off work, without loss of pay, and provide them with the necessary
means to enable such representatives to exercise their rights and functions deriving from this
6. Workers and/or their representatives are entitled to appeal, in accordance with national law and/or
practice, to the authority responsible for safety and health protection at work if they consider that the
measures taken and the means employed by the employer are inadequate for the purposes of
ensuring safety and health at work.
Workers' representatives must be given the opportunity to submit their observations during
inspection visits by the competent authority.
1. ÌEC TR 60825-14: 2004 recommends a minimum training requirement for laser users
2. EN 60825-2: 2004 specifies additional requirements for users working on optical fibre
3. EN 60825-12: 2004 specifies additional requirements for users working on free-space
4. CLC/TR 50448: 2005 provides a guide to levels of competency required in laser safety
9.6 PersonaI Protective Equipment
Reduction of unintended exposure to optical radiation should be included in the design
specifications of the equipment. Exposure to optical radiation should be reduced, as far
as reasonably practicable, by means of physical safeguards, such as engineering
controls. Personal protective equipment should only be used when engineering and
administrative controls are impracticable or incomplete.
The purpose of PPE is to reduce optical radiation to the level which does not cause
adverse health effects in the exposed individual. The optical radiation injuries may not
be apparent at the time of the exposure. Ìt should be noted that Exposure Limits are
wavelength dependent, therefore the degree of protection offered by PPE may also be
wavelength dependent.
Although an acute skin injury resulting from exposure to optical radiation is less likely
to affect the individual's quality of life, it should be recognised that the probability of
skin injury may be high, especially for hands and face. Exposure of the skin to optical
radiation below 400 nm, which may increase the risk of skin cancer, is of particular
PPE should be appropriate for the risks involved, without itself
leading to any increased risk
PPE should be appropriate for the conditions at the workplace
PPE should take account of ergonomic requirements and the
worker's state of health
9.6.1 Protection against other hazards
The following non-optical hazards should also be considered when selecting
appropriate PPE to protect against exposure to optical radiation:
Ìmpact Heat/Cold
Penetration Harmful dust
Compression Biological
Chemical Electrical
Examples are given in Table below:
9.6.2 Eye protection
The eye is at risk of injury from optical radiation if exposures are in excess of the
Exposure Limit Values (ELVs). Ìf the other measures are inadequate to control the risk
of eye exposure in excess of any applicable ELVs, eye protection recommended by the
equipment manufacturer or optical radiation safety advisor and specifically designed for
the wavelengths and output should be worn.
Protective eyewear should be clearly marked with the wavelength range and
corresponding protection level. This is particularly important if there are multiple
sources that require different types of protective eyewear, such as different wavelength
lasers that require their own unique eyewear. Additionally, it is recommended that an
unambiguous and robust method of marking the safety eyewear should be employed to
ensure that there is a clear link to the particular equipment for which PPE has been
The level of attenuation of optical radiation provided by protective eyewear in the
hazard spectral region should be, at least, sufficient to decrease the exposure level
below applicable ELVs.
Luminous transmittance and the colour of the environment as seen through the
protective filters are important characteristics of eyewear which may affect the
operator's ability to perform the required operations without compromising non-optical
Protective eyewear should be correctly stored, regularly cleaned, and subject to a
defined inspection regime.
Protective eyewear:
safety spectacles,
goggles, face shields,
Eyewear should allow the worker to see everything in the work area but
restrict the optical radiation to acceptable levels. Selection of appropriate
eyewear depends upon many factors including: wavelength, power/energy,
optical density, need for prescription lenses, comfort, etc.
Sources of optical radiation may present a fire hazard and protective
clothing may be necessary.
Equipment that produces UV radiation may present a skin hazard and skin
should be covered using suitable protective clothing and gloves. Gloves
should be worn when working with chemical or biological agents. Protective
clothing or gloves may be required by application specifications.
Toxic and harmful fumes or dusts may be produced during processing.
Respiratory equipment may be necessary for emergency use.
Ear defenders Noise can be a hazard from some industrial applications.
9.6.3 Skin protection
For occupational exposure to optical radiation, the areas of the skin most usually at risk
are the hands, the face, the head and the neck, as other areas are generally covered
by working clothes. The hands can be protected by wearing gloves with low
transmission to hazardous optical radiation. The face can be protected by an absorbing
face shield or visor, which may also offer eye protection. Suitable headwear will protect
the head and neck.
Considerations for choice of protective eyewear
Q: Level of protection
Q: Luminous transmittance?
Quality of vision?
Choose eyewear with luminous transmittance >20%
Ìf not available, increase illumination level
Check filters for scratches and scatter
Q: Too much reflections? Avoid mirror finish or high gloss filters and frames
Q: Colour perception of the
Check that equipment controls and emergency
signs are clearly seen through protective eyewear
Q: Ìf eyewear is powered by mains
or batteries and power is
interrupted, does it fail to safety?
Choose filter that provides maximum
attenuation when not powered
Choose eyewear with the attenuation >
IeveI exp
9.7 Further usefuI information
Council Directive 89/656/EEC on the minimum health and safety requirements for the
use by workers of personal protective equipment at the workplace
9.7.1 Basic standards
EN 165: 2005 ÷ Personal eye-protection - Vocabulary
EN 166: 2002 ÷ Personal eye-protection - Specifications
EN 167: 2002 ÷ Personal eye-protection - Optical test methods
EN 168: 2002 ÷ Personal eye-protection - Non-optical test methods
9.7.2 Standards by type of product
EN 169: 2002 ÷ Personal eye-protection - Filters for welding and related techniques -
Transmittance requirements and recommended use
EN 170: 2002 ÷ Personal eye-protection - Ultraviolet filters - Transmittance
requirements and recommended use
EN 171: 2002 ÷ Personal eye-protection - Ìnfrared filters - Transmittance requirements
and recommended use
9.7.3 WeIding
EN 175: 1997 ÷ Personal protection - Equipment for eye and face protection during
EN 379: 2003 ÷ Personal eye-protection ÷ Automatic welding filters
EN 1598: 1997 Health and safety in welding and allied processes - Transparent
welding curtains, strips and screens for arc welding processes
MANAGÌNG ADVERSE ÌNCÌDENTS
9.7.4 Laser
EN 207: 1998 ÷ Filter and eye protectors against laser radiation
EN 208: 1998 ÷ Eye protectors for adjustment work on lasers and laser systems
9.7.5 Intense Iight sources
BS 8497-1: 2008. Eyewear for protection against intense light sources used on
humans and animals for cosmetic and medical applications. Part 1: Specification for
BS 8497-2: 2008. Eyewear for protection against intense light sources used on
humans and animals for cosmetic and medical applications. Part 2: Guidance on use
10 MANAGING ADVERSE INCIDENTS
Within the context of this Guide, adverse incidents include situations where someone is
injured or falls ill (termed accidents), or near misses or undesired circumstances
(termed incidents).
Where collimated laser beams are used, the risk of getting exposed to the laser beam
is generally low, but the consequence may be high. Ìn contrast, with non-coherent
sources of artificial optical radiation, the risk of getting exposed is high, but the
consequence may be low.
Ìt is suggested that contingency plans are prepared to deal with reasonably
foreseeable adverse events involving artificial optical radiation. The level of detail and
complexity will depend on the risk. Ìt is likely that the employer will have general
contingency arrangements so there will be an advantage in using similar approaches
for optical radiation.
Ìt is suggested that detailed contingency plans should be prepared for work
practices where access to optical radiation from the following is likely:
Class 3B Lasers
Risk Group 3 Non-coherent sources
The contingency plans should address actions and responsibilities in the event of:
An actual worker exposure in excess of the ELV
A suspected worker exposure in excess of the ELV
11 HEALTH SURVEILLANCE
Article 8 of the Directive describes the requirements for health surveillance, referencing
the general requirements of Directive 89/391/EEC. The detail for any health
surveillance is likely to rely on National requirements. Therefore, the proposal
presented in this Chapter is very generic.
The requirements of this Article need to be considered in the context of over one
hundred years of worker exposure to artificial optical radiation. The number of reported
adverse health effects are small, and restricted to a small number of industries, where
control measures have generally been implemented to reduce the number of
incidences even further.
Following the invention of the laser, recommendations were published on routine eye
examinations for laser workers. However, nearly 50 years of experience has shown
that such examinations have no value as part of a health surveillance programme and
possibly introduce an additional risk to the worker.
A worker exposed to artificial optical radiation at work should not receive pre-
employment, routine and post-employment eye examinations, just because they carry
out such work. Similarly, skin examinations may be of benefit to workers, but are not
usually justified purely on the basis of routine exposure to artificial optical radiation.
11.1 Who shouId carry out the HeaIth SurveiIIance?
Health surveillance should be carried by:
A doctor;
An occupational health professional; or
A medical authority responsible for health surveillance in accordance with national
law and practice.
11.2 Records
Member States are responsible for establishing arrangements to ensure that individual
records are made and kept up to date. The records should contain a summary of the
results of the health surveillance carried out.
The records should be in a form so that they can be consulted at a later date, taking
account of confidentiality.
Ìndividual workers should have access to their own records on request.
HEALTH SURVEÌLLANCE
11.3 MedicaI Examination
A medical examination should be made available to a worker if it is suspected or
known that they have been exposed to artificial optical radiation in excess of the
exposure limit value.
A medical examination should be carried out if a worker is found to have an identifiable
disease or adverse health effects, which is considered to be a result of exposure to
artificial optical radiation.
A challenge for implementing this requirement is that many adverse health effects may
be due to exposure to natural optical radiation. Therefore, it is important that the
person carrying out the medical examination is familiar with the potential adverse
health effects from the specific sources of workplace exposure to artificial optical
11.4 Actions if an exposure Iimit is exceeded
Ìf the exposure limits are thought to have been exceeded or if the adverse health effect
or identifiable disease is considered to have been caused by artificial optical radiation
in the workplace then the following actions should be triggered:
The worker should be informed of the results
The worker should receive information and advice regarding follow-up health
The employer should be informed, respecting any medical confidentiality
The employer should review the risk assessment
The employer should review the existing control measures (which may involve
seeking specialist advice)
The employer should arrange any necessary continued health surveillance.
APPENDIX A Nature of OpticaI Radiation
Light is an everyday example of optical radiation ÷ artificial optical radiation, if it is
emitted by a lamp. The term "optical radiation¨ is used because light is a form of
electromagnetic radiation, and because it has effects on the eye ÷ i.e. it enters the eye,
is focussed and then detected.
Light comes in a spectrum of colours, ranging from purples and blues through greens
and yellows to oranges and reds. The colours that we perceive in light are determined
by the wavelengths present in the light spectrum. Shorter wavelengths are perceived as
lying at the blue end of the spectrum, and longer wavelengths at the red end. Ìt is
convenient to consider light to consist of a stream of massless particles, called photons,
each of which has a characteristic wavelength.
The spectrum of electromagnetic radiation extends far beyond those wavelengths that
we are able to see. Ìnfrared radiation, microwave radiation and radio waves are
examples of electromagnetic radiation with increasingly long wavelengths. Ultraviolet
radiation, x-rays and gamma rays have increasingly short wavelengths.
The wavelength of an electromagnetic radiation can be used to determine other useful
Whenever electromagnetic radiation interacts with a material, it is likely to deposit some
energy at the point of interaction. This may cause some effect in the material ÷ for
example, visible light arriving at the retina deposits enough energy to trigger biochemical
reactions which produce a signal sent via the optic nerve to the brain. The amount of
energy available for such interactions depends on both the quantity of radiation and on
how energetic the radiation happens to be. The amount of energy available in
electromagnetic radiation can be related to the wavelength. The shorter the wavelength,
the more energetic the radiation is. Thus, blue light is more energetic than green light
which, in turn, is more energetic than red light. Ultraviolet radiation is more energetic
than any visible wavelength.
The wavelength of radiation also determines the degree to which it penetrates and
interacts with the body. For example, UVA is transmitted to the retina less efficiently
than green light
Some of the invisible portions of the electromagnetic spectrum are included in the term
"optical radiation¨. These are the ultraviolet and infrared spectral regions. Although they
cannot be seen (the retina doesn't have detectors for these wavelengths) portions of
these spectral regions can penetrate the eye, to a greater or lesser degree. For
convenience, the optical radiation spectrum is divided up, by wavelength, as follows:
Ultraviolet "C¨ (UVC): 100 ÷ 280 nm
UVB 280 ÷ 315 nm
UVA 315 ÷ 400 nm
Visible 380 ÷ 780 nm
APPENDÌX A
Infrared "A¨ (ÌRA) 780 ÷ 1400 nm
ÌRB 1400 ÷ 3000 nm
ÌRC 3000 ÷ 1000000 nm (3 m ÷ 1 mm)
The Directive contains exposure limits covering the spectral region 180 ÷ 3000 nm for
non-coherent optical radiation and from 180 nm to 1 mm for laser radiation.
APPENDIX B BioIogicaI effects of opticaI radiation to the eye
B1 THE EYE
Figure B1. Structure of the eye
Light entering the eye passes through the cornea, aqueous, then through a variable
aperture (pupil), and through the lens and vitreous to be focused on the retina. The optic
nerve carries signals from the photoreceptors of the retina to the brain.
Figure B2. Penetration of different waveIength through the eye
APPENDÌX B
B2 THE SKIN
Figure B3. The structure of the skin
The outer layer of the skin, the epidermis, contains mainly keratinocytes (squamous
cells) which are produced in the basal layer and rise to the surface to be sloughed off.
The dermis is composed mainly of collagen fibres and contains nerve endings, sweat
glands, hair follicles and blood vessels.
Figure B4. Penetration of different waveIength through the skin
B3 BIOLOGICAL EFFECT OF DIFFERENT WAVELENGTH TO THE
EYE AND THE SKIN
B3.1 UItravioIet radiation: UVC (100-280nm); UVB (280-315nm); UVA (315-
400 nm)
Much of any ultraviolet radiation (UVR) incident on the skin is absorbed in the epidermis,
although penetration increases markedly for the longer UVA wavelengths.
Excessive short-term exposure to UV radiation causes erythema - a reddening of the
skin, and swelling. Symptoms can be severe, and the maximum effect occurs 8-24
hours after exposure, subsiding over 3-4 days with subsequent dryness and skin
peeling. This may be followed by an increase in skin pigmentation (delayed tanning).
Exposure to UVA radiation can also cause an immediate but temporary change in skin
pigmentation (Ìmmediate Pigment Darkening).
Some people have abnormal skin responses to UVR exposure (photosensitivity)
because of genetic, metabolic, or other abnormalities, or because of intake or contact
with certain drugs or chemicals.
The most serious long-term effect of UV radiation is the induction of skin cancer. The
non-melanoma skin cancers (NMSCs) are basal cell carcinomas and squamous cell
carcinomas. They are relatively common in white people, although they are rarely fatal.
They occur most frequently on sun-exposed areas of the body such as the face and
hands and show an increasing incidence with increasing age. The findings from
epidemiological studies indicate that the risk of both of these skin cancers can be
related to cumulative UV radiation exposure, although the evidence is stronger for
squamous cell carcinomas. Malignant melanoma is the main cause of skin cancer
death, although its incidence is less than NMSC. A higher incidence is found in people
with large numbers of naevi (moles), those with a fair skin, red or blond hair and those
with a tendency to freckle, to sunburn and not to tan on sun exposure. Both acute
burning episodes of sun exposure and chronic occupational and recreational exposure
may contribute to the risk of malignant melanoma.
Chronic exposure to UVR can also cause photoageing of the skin, characterised by a
leathery wrinkled appearance and loss of elasticity: UVA wavelengths are the most
effective as they can penetrate to the collagen and elastin fibres of the dermis. There is
also evidence suggesting that exposure to UVR can affect immune responses.
The main known beneficial effect of UVR exposure is the synthesis of vitamin D;
although short exposures to sunlight in everyday life will produce sufficient vitamin D if
dietary intake is inadequate.
UVR falling on the eye is absorbed by the cornea and lens. The cornea and conjunctiva
absorb strongly at wavelengths shorter than 300 nm. UVC is absorbed in the superficial
layers of the cornea and UVB is absorbed by the cornea and lens. UVA passes through
the cornea and is absorbed in the lens.
Responses of the human eye to acute overexposure of UVR include photokeratitis and
photoconjunctivitis (inflammation of the cornea and the conjunctiva, respectively), more
commonly known as snow blindness, arc-eye or welder's flash. Symptoms, ranging from
mild irritation, light sensitivity and tearing to severe pain, appear within 30 minutes to a
day depending on the intensity of exposure and are usually reversible in a few days.
Chronic exposure to UVA and UVB can cause cataracts due to protein changes in the
lens of the eye. Very little UV (less than 1% UVA) normally gets through to retina due to
absorption by the anterior tissues of the eye. However, there are some people who do
not have a natural lens as a result of cataract surgery, and unless there is an implanted
artificial lens which absorbs it, the retina can be damaged by UVR (at wavelengths as
short as 300 nm) entering the eye. This damage is a result of photochemically produced
free radicals attacking the structures of the retinal cells. The retina is normally protected
from acute damage by involuntary aversion responses to visible light, but UVR does not
produce these responses: persons lacking a UVR absorbing lens are therefore at higher
risk of suffering retinal damage if working with UVR sources.
Chronic UVR exposure is a major contributor to the development of corneal and
conjunctival disorders such as climatic droplet keratopathy (an accumulation of
yellow/brown deposits in the conjunctiva and cornea), pterygium (an overgrowth of
tissue which may spread over the cornea) and probably pinguecula (a proliferative
yellow lesion of the conjunctiva).
B3.2 VisibIe radiation
Visible radiation (light) penetrates into the skin and may raise the local temperature
enough to cause burning. The body will adjust to gradual temperature rises by
increasing blood flow (which carries heat away) and perspiration. Ìf the irradiation is
insufficient to cause an acute burn (in 10 s or less), the exposed person will be
protected by natural aversion responses to heat.
For long exposure durations, heat strain from thermal stress (increased core body
temperature) is the principal adverse effect. Although this is not specifically covered by
the Directive, ambient temperature and work load must be considered.
Because the eyes act to collect and focus visible radiation, the retina is at greater risk
than the skin. Gazing at a bright light source can cause retinal damage. iÌ the lesion is in
the fovea, e.g. if looking directly along a laser beam, severe visual handicap may result.
Natural protective measures include an aversion to bright light (the aversion response
operates in about 0.25 seconds; the pupil contracts and can reduce retinal irradiance by
about a factor of 30; and the head may be turned involuntarily away)
Retinal temperature increases of 10 ÷ 20 °C can lead to irreversible damage due to
denaturation of proteins. Ìf the radiation source covers a large part of the field of view so
that the retinal image is large, it is difficult for the retinal cells in the central region of the
image to shed heat quickly.
Visible radiation can cause the same type of photochemically induced damage as UVR
(although, at visible wavelengths, the aversion to bright light can act as a protective
mechanism). This effect is most pronounced at wavelengths around 435-440 nm, and
so it is sometimes called the "blue-light hazard¨. Chronic exposure to high ambient
levels of visible light may be responsible for photochemical damage to the cells of the
retina, resulting in poor colour and night vision.
Where radiation enters the eye in an essentially parallel beam (i.e. very low divergence
from a distant source or a laser) it may be imaged onto the retina in a very small area,
concentrating the power tremendously and resulting in severe damage. This focussing
process could in theory increase the irradiance on the retina compared to that falling on
the eye by up to 500,000 times. Ìn these cases, the brightness can exceed all known
natural and man-made light sources. Most laser injuries are burns: pulsed high peak
power lasers can produce such a rapid rise in temperature that cells literally explode.
B3.3 IRA
ÌRA penetrates several millimetres into tissue, that is, well into the dermis. Ìt can
produce the same thermal effects as visible radiation.
Like visible radiation, ÌRA is also focussed by the cornea and lens and transmitted to the
retina. There, it can cause the same sort of thermal damage as visible radiation can.
However, the retina does not detect ÌRA, and so there is no protection from natural
aversion responses. The spectral region from 380 to 1400 nm (visible and ÌRA) is
sometimes called the "retinal hazard region¨.
Chronic exposure to ÌRA may also induce cataracts.
ÌRA does not have sufficiently energetic photons for there to be a risk of
photochemically induced damage.
B3.4 IRB
ÌRB penetrates less than 1 mm into tissue. Ìt can cause the same thermal effects as
visible radiation and ÌRA.
At wavelengths around 1400 nm, the aqueous humour is a very strong absorber; and
longer wavelengths are attenuated by the vitreous humour, thus the retina is protected.
Heating of the aqueous humor and iris can raise the temperature of the adjacent
tissues, including the lens, which is not vascularised and so cannot control its
temperature. This, along with direct absorption of ÌRB by the lens induces cataracts,
which have been an important occupational disease for some groups, principally glass
blowers and chain makers.
B3.5 IRC
ÌRC penetrates only to the uppermost layer of dead skin cells (stratum corneum).
Powerful lasers, which may be capable of ablating the stratum corneum and damaging
underlying tissues, are the most serious acute hazard in the ÌRC region. The damage
mechanism is mainly thermal, but high peak power lasers may cause
mechanical/acoustic damage.
As for visible, ÌRA and ÌRB wavelengths, heat strain and discomfort from thermal stress
ÌRC is absorbed by the cornea, and so the main hazard is corneal burns The
temperature in adjacent structures of the eye may increase due to thermal conduction,
but heat loss (by evaporation, and blinking) and gain (due to body temperature) will
influence this process.
APPENDIX C ArtificiaI OpticaI Radiation Quantities & Units
As pointed out in the section on "The Nature of Optical Radiation¨, the effects of optical
radiation depend on the energy of the radiation and the quantity of radiation. There are
many ways of quantifying optical radiation: those used in the Directive are outlined
briefly below.
C1 FUNDAMENTAL QUANTITIES
C1.1 WaveIength
This refers to the characteristic wavelength of the optical radiation. Ìt is measured in
small sub-divisions of the metre ÷ usually the nanometre (nm), which is equal to one
millionth of one millimetre. At longer wavelengths, it is sometimes more convenient to
use the micrometre ( m). One micrometre is equal to 1000 nanometres.
Ìn many cases, the optical radiation source under consideration will be emitting photons
of many different wavelengths.
When writing formulae, wavelength is represented by the symbol (lambda).
C1.2 Energy
This is measured in joules (J). Ìt may be used to refer to the energy of each photon
(which is related to the photon's wavelength). Ìt may also refer to the energy contained
in a given quantity of photons, for example, a laser pulse.
Energy is represented by the symbol Q.
C1.3 Other usefuI quantities
Angular subtense
This is the apparent width of an object (usually an optical radiation source) as seen from
some location (usually the point at which measurements are being made). Ìt is
calculated by dividing the true width of the object by the distance to the object. Ìt is
important that both of these values are in the same units. Whatever units these values
are in, the resulting angular subtense is in radians (r).
Ìf the object is at an angle to the viewer, the angular subtense must be multiplied by the
cosine of the angle.
Angular subtense is represented in the Directive by the symbol (alpha).
Solid angular subtense
This is the three-dimensional equivalent of the angular subtense. The area of the object
is divided by the square of the distance. Again, the cosine of the viewing angle may be
used to correct for off-axis viewing. The unit is the steradian (sr) and the symbol is
(omega).
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@+ * * * 3 . # 7 .)$= + ' @# . 2# ! # # # 5 # # 2 # # 7 # # # A 4# -# 2 # 5 ! # # 1 . # # 2 ! . @) * D 3 0 0 # 1 B ## # .
.5 # ## . .)%)* )$= .. D . ! ## A ? 7 B # 7 ? -# # # 2# 2 1 ! * .& # 5 + . . # 1 . 7 # 4. " @) ) G- H67 E %%2#/% . A = $ 7 B5 3 2 1 0 . 1 7 ! # ! # ? . GI67 E () . $ 0= = 8% 0= 8 >= $= 0= $= %) 0= / @) @ . ? # 7 # 1 5 3 . # # # - 9 2 5? . #0 5 ## 5 ! ! 2 # # # @ ? # # 0 & # . . 2. # 2 #! -# & # .. 5 0 # 4# *& # . ! ## # 4-# # G 5 # -# # 7 # # # # )G3 5 # . & # . .# - $C $ ) ? 2# 2 # # # 2# 2 2 ## ? + # 2# 2 # 2# 2 # 5 1 ! #0 5 # 2# 2 #? 5 F .! ? & # . # 2 # # # # 1 # 1 # 5 0 # .. 7 2.. -# # # -# # 7 * ! 2 2 # 5 # 7 & #1 # -2# 4# . -# A . ? # -# . G . 2 ? # 2 & # . #. -# . # 7 B5 # 7 # ## . GI67@ E #/%2) ( .# # 7 2 # # 7 # 2 . 4 7 .?= 0% 0 += ). 7 # # ! B ? # # 7 50 #A )G3 # B 2# # # 4-# #0 5 ! 1 .! # -. # # ? ? ! & # . 2# 7 5 * & # . . . # 7 1 ! 2 # # # # . 1 . # 5 # & # ! # * # & # . # -2# ! 9* . # # A -# *.# # # . - - 7 1 2 # & # # # . # # -# .2 # ! A # B # 1 # 7 2 # 1 7 # 2# . 5 0 # 2 1 2 # & # . -. " F 6 +%% .& # .
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
# -. # . 7 .B 1 / .# #1 #. 2 # # -# 25 =+1 ! 5 # #A # " = 50 .. # # # # # .# 2# .# .# # # # -# -.. # # # # @) ( ) = 1 . =+ 2 -. . # 2 . #5 # .# # A # 2 ! . .B5 2 - -# # ! #2 = -# 2 # ) = # # # # # # 2# 2 2 # F #. . 2 7 B 2#. 1 # # # 7 # . " # # A2 2.# # . 7 # 5 # ! #.5 0 # 1 ! 2 2 1 # # 1 1 .# 0 .)$= + ' #.
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