IEC 60825-4:2022
(Main)Safety of laser products - Part 4: Laser guards
Safety of laser products - Part 4: Laser guards
IEC 60825-4:2022 deals with basic issues concerning laser guards, including human access, interlocking and labelling, and gives general guidance on the design of protective housings and enclosures for high-power lasers. Laser guards may also comply with standards for laser protective eyewear, but such compliance is not necessarily sufficient to satisfy the requirements of this document. This part of IEC 60825 specifies the requirements for laser guards, permanent and temporary (for example for service), that enclose the process zone of a laser processing machine, and specifications for proprietary laser guards. This document applies to all component parts of a guard including clear (visibly transmitting) screens and viewing windows, panels, laser curtains and walls. In addition, this document indicates
- how to assess and specify the protective properties of a laser guard, and
- how to select a laser guard.
Sécurité des appareils à laser - Part 4: Protecteurs pour lasers
L’IEC 60825-4:2022 traite de questions fondamentales concernant les protecteurs pour laser, y compris l’accès humain, les dispositifs d'interverrouillage et l’étiquetage, et fournit des recommandations générales relatives à la conception de capots et d’enceintes de protection pour les lasers de forte puissance. Les protecteurs pour laser peuvent également être conformes aux normes pour les protecteurs oculaires contre le rayonnement laser, mais une telle conformité n’est pas nécessairement suffisante pour satisfaire aux exigences du présent document. La présente partie de l’IEC 60825 spécifie les exigences relatives aux protecteurs pour laser, permanents et temporaires (par exemple, pour l’entretien), qui protègent la zone de traitement d’une machine à laser, ainsi que les spécifications pour les protecteurs d'origine pour laser. Le présent document s’applique à tous les composants d’un protecteur, y compris les écrans clairs (visiblement transmetteurs) et les fenêtres d’observation, les panneaux, les rideaux pour laser et les parois. De plus, le présent document indique
- comment évaluer et spécifier les propriétés de protection d’un protecteur pour laser, et
- comment sélectionner un protecteur pour laser.
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Standards Content (Sample)
IEC 60825-4 ®
Edition 3.0 2022-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Safety of laser products –
Part 4: Laser guards
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IEC 60825-4 ®
Edition 3.0 2022-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Safety of laser products –
Part 4: Laser guards
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.260 ISBN 978-2-8322-4407-4
– 2 – IEC 60825-4:2022 RLV © IEC 2022
CONTENTS
FOREWORD . 5
INTRODUCTION . 2
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Laser processing machines Requirements for laser guards. 12
4.1 Requirement . 12
4.2 Design requirements . 12
4.3 Performance requirements . 12
4.4 Validation . 13
4.5 User information . 13
5 Proprietary laser guards . 13
5.1 General . 13
5.2 Design requirements . 13
5.3 Performance requirements . 13
5.4 Specification requirements . 14
5.5 Test requirements . 14
5.6 Labelling requirements . 15
5.7 User information . 15
Annex A (informative) General guidance on the design and selection of laser guards . 16
A.1 Design of laser guards . 16
A.2 Selection of laser guards . 16
Annex B (informative) Assessment of foreseeable exposure limit (FEL) . 18
B.1 General . 18
B.2 Reflection of laser radiation . 19
B.3 Examples of assessment conditions . 19
B.4 Exposure duration . 22
B.5 Reference document .
Annex C (informative) Elaboration of defined terms . 25
C.1 Distinction between FEL and PEL . 25
C.2 Active guard parameters . 25
Annex D (normative) Proprietary laser guard testing . 27
D.1 General . 27
D.2 Test conditions . 27
D.3 Protection time corresponding to the specified protective exposure limit
(PEL) . 31
D.4 Information supplied by the manufacturer. 31
Annex E (informative) Guidelines on the arrangement and installation of laser guards . 33
E.1 Overview. 33
E.2 General . 33
E.3 Risk assessment . 34
E.4 Examples of risk assessment . 36
E.5 Aids to risk assessment . 39
Annex F (informative) Guideline for assessing the suitability of laser guards . 42
F.1 Identification of hazards . 42
F.2 Risk assessment and integrity . 42
F.3 General design . 45
F.4 Selection of safeguards . 46
F.5 Guard design and construction . 46
F.6 Guard construction and materials . 48
F.7 Other safety devices . 50
F.8 Interlocking considerations . 51
F.9 Environmental considerations . 55
F.10 Installation consideration – Environmental factors – Services . 56
F.11 Maintenance and service considerations . 56
Annex G (normative) Guided beam delivery systems . 67
G.1 General . 67
G.2 Terms and definitions .
G.2 General requirements . 67
G.3 Verification of safety requirements or protective measures . 70
G.4 Information for users . 70
G.5 Examples of risk assessments . 71
Bibliography . 76
Figure B.1 – Calculation of diffuse reflections . 19
Figure B.2 – Calculation of specular reflections . 19
Figure B.3 – Some examples of a foreseeable fault condition . 20
Figure B.4 – Four examples of errant laser beams that might have to be contained by a
temporary guard under service conditions . 21
Figure B.5 – Illustration of laser guard exposure during repetitive machine operation . 22
Figure B.6 – Two examples of assessed duration of exposure . 23
Figure B.7 – Assessed duration of exposure for a machine with no safety monitoring . 24
Figure C.1 – Illustration of guarding around a laser processing machine . 25
Figure C.2 – Illustration of active laser guard parameters . 26
Figure D.1 – Simplified diagram of the test arrangement . 29
Figure D.2 – Simplified diagram of the ventilation for the guard under test . 29
Figure F.1 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW CO laser . 57
Figure F.2 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser . 58
Figure F.3 – Damage resistance of 2 mm thick zinc coated steel sheet derived from 10
s exposure to a defocused beam during experiments using a CW CO laser . 58
Figure F.4 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser . 58
Figure F.5 – Damage resistance of 3 mm thick zinc coated steel sheet derived from 10
s exposure to a defocused beam during experiments using a CW CO laser . 59
Figure F.6 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser . 59
Figure F.7 – Damage resistance of 2 mm thick aluminium sheet derived from 10 s
exposure to a defocused beam during experiments using a CW CO laser . 59
– 4 – IEC 60825-4:2022 RLV © IEC 2022
Figure F.8 – Damage resistance of 2 mm thick aluminium sheet derived from 100 s
exposure to a defocused beam during experiments using a CW CO laser . 60
Figure F.9 – Damage resistance of 1 mm thick stainless steel sheet derived from 10 s
exposure to a defocused beam during experiments using a CW CO laser . 60
Figure F.10 – Damage resistance of 1 mm thick stainless steel sheet derived from 100
s exposure to a defocused beam during experiments using a CW CO laser . 60
Figure F.11 – Damage resistance of 6 mm thick polycarbonate sheet derived from 10 s
exposure to a defocused beam during experiments using a CW CO laser . 61
Figure F.12 – Damage resistance of 6 mm thick polycarbonate sheet derived from 100
s exposure to a defocused beam during experiments using a CW CO laser . 61
Figure F.13 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 62
Figure F.14 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 62
Figure F.15 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 63
Figure F.16 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 63
Figure F.17 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 64
Figure F.18 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 64
Figure F.19 – Damage resistance of 2 mm thick aluminium sheet derived from 10 s
exposure to a defocused beam during experiments using a CW Nd:YAG laser . 65
Figure F.20 – Damage resistance of 2 mm thick aluminium sheet derived from 100 s
exposure to a defocused beam during experiments using a CW Nd:YAG laser . 65
Figure F.21 – Damage resistance of 1 mm thick stainless steel sheet derived from 10 s
exposure to a defocused beam during experiments using a CW Nd:YAG laser . 66
Figure F.22 – Damage resistance of 1 mm thick stainless steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 66
Table D.1 – Laser guard test classification . 30
Table F.1 – Application of ALARP . 45
Table G.1 – Beam delivery systems using free space beam delivery systems . 71
Table G.2 – Beam delivery systems using fibre optic cables . 73
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF LASER PRODUCTS –
Part 4: Laser guards
FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes made to
the previous edition IEC 60825-4:2006+AMD1:2008+AMD2:2011 CSV. A vertical bar appears in
the margin wherever a change has been made. Additions are in green text, deletions are in
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– 6 – IEC 60825-4:2022 RLV © IEC 2022
IEC 60825-4 has been prepared by IEC technical committee 76: Optical radiation safety and
laser equipment. It is an International Standard.
This third edition cancels and replaces the second edition published in 2006,
Amendment 1:2008 and Amendment 2:2011. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Significant amendments have been included and this edition has been prepared for user
convenience.
The text of this International Standard is based on the following documents:
Draft Report on voting
76/704/FDIS 76/711/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
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INTRODUCTION
At low levels of irradiance or radiant exposure, the selection of material and thickness for
shielding against laser radiation is determined primarily by a need to provide sufficient optical
attenuation. However, at higher levels, an additional consideration is the ability of the laser
radiation to remove guard material – typically by melting, oxidation or ablation; processes that
could lead to laser radiation penetrating a normally opaque material.
IEC 60825-1 deals with basic issues concerning laser guards, including human access,
interlocking and labelling, and gives general guidance on the design of protective housings and
enclosures for high-power lasers.
Laser guards may also comply with standards for laser protective eyewear, but such compliance
is not necessarily sufficient to satisfy the requirements of this document.
Where the term "irradiance" is used, the expression "irradiance or radiant exposure, as
appropriate" is implied.
– 8 – IEC 60825-4:2022 RLV © IEC 2022
SAFETY OF LASER PRODUCTS –
Part 4: Laser guards
1 Scope
This part of IEC 60825 specifies the requirements for laser guards, permanent and temporary
(for example for service), that enclose the process zone of a laser processing machine, and
specifications for proprietary laser guards.
This document applies to all component parts of a guard including clear (visibly transmitting)
screens and viewing windows, panels, laser curtains and walls.
In addition, this document indicates
a) how to assess and specify the protective properties of a laser guard, and
b) how to select a laser guard.
NOTE Requirements for beam path components, beam stops and those other parts of a protective housing of a
laser product which do not enclose the process zone are contained in IEC 60825-1.
This document deals with protection against laser radiation only. Hazards from secondary
radiation that may arise during material processing are not addressed.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60825-1:20072014, Safety of laser products – Part 1: Equipment classification and
requirements
IEC 61508 (all parts), Functional safety of electrical/electronic/programmable electronic safety-
related systems
ISO 11553-1:2005, Safety of machinery – Laser processing machines – Laser safety
requirements
ISO 12100, Safety of machinery – General principles for design – Risk assessment and risk
reduction
ISO 12100-1:2003, Safety of machinery – Basic concepts, general principles for design –
Part 1: Basic terminology, methodology
ISO 12100-2:2003, Safety of machinery – Basic concepts, general principles for design – Part 2:
Technical principles and specifications
ISO 13849-1:2006, Safety of machinery – Safety-related parts of control systems – Part 1:
General principles for design
ISO 14121-1:2007, Safety of machinery – Risk assessment – Part 1: Principles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60825-1 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
access panel
panel which when removed or displaced gives human access to laser radiation
Note 1 to entry: Sheathing around a fibre, tubing used as an enclosure component or any device serving the function
of a removable or displaceable panel, can also be an "access panel" within the terms of this definition.
3.2
active guard protection time
minimum time for a given laser exposure of the front (incident) surface of an active laser guard,
the minimum time, measured from the issue of an active guard termination signal, for which the
active laser guard can safely prevent laser radiation accessible at its rear surface from
exceeding the Class 1 AEL
3.3
active guard termination signal
signal issued by an active guard in response to an excess exposure of its front surface to laser
radiation and which is intended to lead to automatic termination of the laser radiation
Note 1 to entry: The action of a safety interlock becoming open circuit is considered a "signal" in this context.
3.4
active laser guard
laser guard which is part of a safety-related control system whereby failure of the front surface
of the laser guard triggers a termination signal. The control system generates an active guard
termination signal in response to the effect of laser radiation on the front surface of the laser
guard
3.5
beam delivery system
system comprised of all those components, including all optical beam components and potential
beam paths and their enclosures, which when combined, transfer laser radiation emitted from
the laser radiation generator (the laser) to the workpiece
Note 1 to entry: These components may include all elements for guiding, shaping and switching the laser beam as
well as the enclosure of and support for the beam path components. See Annex G for detail on guided beam delivery
systems.
3.6
beam diameter
d
diameter of the smallest circular aperture in a plane perpendicular to the beam axis that contains
86 % of the total laser power (or energy)
Note 1 to entry: In the case of a Gaussian beam (TEM ), d corresponds to the point where the irradiance (radiant
exposure) falls to 1/e of its central peak value and the second order moments of the power density distribution
(ISO 11146-1:2005 3.2).
– 10 – IEC 60825-4:2022 RLV © IEC 2022
3.7
beam path component
optical component which lies on a defined beam path
Note 1 to entry: Examples of a beam path component include a beam steering mirror, a focus lens or a fibre optic
cable connector.
[SOURCE: IEC 60825-1:2014, 3.16, modified — Example has been removed and Note 1 to
entry has been added.]
3.8
beam shaping component
optical component introduced in the beam path to transform the profile or cross-section of the
laser beam by means of apertures, or reflective, refractive or diffractive optical components
3.9
beam switching component
optical component or an assembly of components introduced in the beam path to direct or divert,
under external control, the beam path along predetermined direction(s) with the external control
allowing the beam path to be switched from one predetermined direction to another
3.10
fibre optic cable
optical beam guiding component that enables the transmission of laser radiation along a
transparent medium
Note 1 to entry: A fibre optic cable may have a glass or other core that carries the laser radiation and be surrounded
by cladding. The outside of the fibre is protected by cladding and may be further protected by additional layers of
other material such as a polymer or a metal to protect the fibre from mechanical deformation, the ingress of water,
etc. This term also includes other forms of transmission devices such as waveguides.
3.11
foreseeable exposure limit
FEL
maximum laser exposure on the front surface of the laser guard, within the maintenance
inspection interval, assessed under normal and reasonably foreseeable fault conditions
Note 1 to entry: The full specification of an FEL comprises different elements, including irradiance and exposure
duration. More details are given in Annex B.
3.12
front surface
face of the laser guard intended for exposure to laser radiation
3.13
laser guard
physical barrier which limits the extent of a danger zone by preventing laser radiation accessible
at its rear surface from exceeding the Class 1 AEL
3.14
laser processing machine
machine which uses a laser to process materials and is within the scope of ISO 11553-1
3.15
laser termination time
maximum time taken, from generation of an active guard termination signal, for the laser
radiation to be terminated
Note 1 to entry: Laser termination time does not refer to the response of an active laser guard but to the response
of the laser processing machine, in particular the laser safety shutter.
3.16
maintenance inspection interval
time between successive safety maintenance inspections of a laser guard
3.17
passive guard protection time
minimum time determined for a laser exposure equal to a specified protective exposure limit
(PEL) at the front (incident) surface of a passive laser guard for which the passive laser guard
can reliably prevent laser radiation accessible at its rear surface from exceeding the class 1
AEL
3.18
passive laser guard
laser guard which relies for its operation on its physical properties only
3.19
process zone
zone where the laser beam interacts with the material to be processed
3.20
proprietary laser guard
passive or active laser guard, offered by its a manufacturer as a of laser guards as an
independent product placed on the market with a specified protective exposure limit
3.21
protective exposure limit
PEL
maximum laser exposure of the front surface of a laser guard which is specified to prevents
laser radiation accessible at its rear surface from exceeding the Class 1 AEL for the determined
passive or active guard detection time
Note 1 to entry: In practice, there may be more than one maximum laser exposure.
Note 2 to entry: Different PELs may be assigned to different regions of a laser guard if these regions are clearly
identifiable (for example, a viewing window forming an integral part of a laser guard).
Note 3 to entry: See 5.3 for the performance requirements and 5.4 for the full specification. The full specification of
a PEL comprises different elements, including irradiance and exposure duration.
3.22
rear surface
any surface of a laser guard that is remote from the associated laser radiation and usually
accessible to the user
3.23
reasonably foreseeable
when it is credible and its whose likelihood of occurrence ( or existence)
cannot be disregarded
3.24
safety maintenance inspection
documented inspection performed in accordance with manufacturer’s instructions
3.25
temporary laser guard
substitute or supplementary active or passive laser guard intended to limit the extent of the
danger zone during some service operations of the laser processing machine
– 12 – IEC 60825-4:2022 RLV © IEC 2022
4 Laser processing machines Requirements for laser guards
4.1 Requirement
Clause 4 specifies the requirements for laser guards that enclose the process zone and are
supplied by the laser processing machine manufacturer.
4.2 Design requirements
4.2.1 Guard requirement
A laser guard shall satisfy ISO 12100-2 with respect to the general requirements for guards and
also the more specific requirements with regard to its location and method of fixture. In addition,
the following specific laser requirements shall be met for a laser guard.
4.2.2 General requirements
A laser guard, in its intended location, shall not give rise to any associated hazard at or beyond
its rear surface when exposed to primary laser radiation or secondary optical radiation up to
the foreseeable exposure limit. Annex F provides guidance on assessing the suitability of laser
guards.
NOTE 1 Examples of associated hazards include high temperature, plasma, excessive ultra-violet radiation, the
release of toxic materials, fire, explosion, and electricity.
NOTE 2 See Annex B for assessment of foreseeable exposure limit.
4.2.3 Consumable parts of laser guards
Provision shall be made for the replacement of parts of a laser guard prone to damage by laser
radiation.
NOTE An example of such a part would be a sacrificial or interchangeable screen.
4.3 Performance requirements
4.3.1 General
When the front (incident) surface of a laser guard is subjected to exposure to laser radiation at
the foreseeable exposure limit, the laser guard shall prevent laser radiation accessible at its
rear surface from exceeding the Class 1 AEL at any time over the period of the maintenance
inspection interval. For automated laser processing machines intended for unattended and/or
unsupervised operation, the minimum value of the maintenance inspection interval shall be 8 h.
This requirement shall be satisfied over the intended lifetime of the laser guard under expected
conditions of operation.
NOTE 1 This requirement implies both low transmission of laser radiation and resistance to laser-induced damage.
NOTE 2 Some materials may can lose their protective properties due to ageing, exposure to ultraviolet radiation,
certain gases, temperature, humidity and other environmental conditions. Additionally, some materials will transmit
laser radiation under high-intensity laser exposure, even though if there may be is no visible damage (i.e. reversible
bleaching).
4.3.2 Active laser guards
a) The active guard protection time shall exceed the laser termination time up to the
foreseeable exposure limits.
b) The generation of an active guard termination signal If an active guard detects an excessive
exposure, i.e. is triggered, it shall give rise to a visible or audible warning. A manual reset
is required before laser emission can recommence.
NOTE See Annex C for an elaboration of terms.
4.4 Validation
4.4.1 General guard validation
If the laser processing machine manufacturer chooses to make a laser guard, the manufacturer
shall confirm that the guard complies with the design requirements and can satisfy the
performance requirements set out in 4.3.
NOTE See Annex A for guidance on the design and selection of laser guards.
4.4.2 Validation of performance
4.4.2.1 The complete laser guard, or an appropriate sample of the material of construction
of the laser guard, shall be tested at each FEL identified.
NOTE 1 It is intended that a table of predetermined PELs for common combinations of lasers
and guarding materials, together with suitable testing procedures, shall will be issued as an
informative annex in a future amendment to this document. This could provide a simple
alternative to direct testing for the majority of cases.
NOTE 2 See Annex B for the assessment of FEL and Annex C for further elaboration of the terms PEL and FEL.
4.4.2.2 For testing purposes, the FEL exposure shall be achieved either:
a) by calculating or measuring the exposure and reproducing the conditions; or
b) without quantifying the FEL, by creating the machine conditions under which the FEL is
produced.
The condition of the laser guard or sample shall be such as to replicate those physical
conditions of the front surface permitted within the scope of the routine inspection instructions
and within the service life of the guard, which minimize the laser radiation protective properties
of the laser guard (for example, wear and tear and surface contamination) (see 4.5.2).
4.5 User information
4.5.1 The manufacturer shall document and provide to the user the maintenance inspection
interval for the laser guard, and details of inspection and test procedures, cleaning, replacement
or repair of damaged parts, together with any restrictions of use.
4.5.2 The manufacturer shall document and provide to the user instructions that after any
actuation of the safety control system of an active guard, the cause shall be investigated, and
checks shall be made for damage, and. The instructions shall also include the necessary
remedial action to be taken before resetting the control system.
5 Proprietary laser guards
5.1 General
Clause 5 specifies the requirements to be satisfied by suppliers of proprietary laser guards.
5.2 Design requirements
A proprietary laser guard shall not create any associated hazard at or beyond its rear surface
when exposed to laser radiation up to the specified PEL when used as specified in the user
information (see 5.7).
5.3 Performance requirements
The accessible laser radiation at the rear surface of the laser guard shall not exceed the
Class 1 AEL when its front surface is subjected to laser radiation at the specified PEL at least
– 14 – IEC 60825-4:2022 RLV © IEC 2022
during the passive guard protection time. For an active laser guard, this requirement shall apply
to laser radiation accessible over the period of the active guard protection time, measured from
the moment an active guard termination signal is issued.
This requirement shall be satisfied over the intended lifetime of the guard under expected
service conditions.
5.4 Specification requirements
The full specification of a PEL shall include the following information:
a) the magnitude and variation with time of irradiance or radiant exposure at the front surface
−2 −2
of the laser guard (in units of W m or J m , respectively) used to measure its passive
guard protection time and mean value and standard deviation of its tested exposure time
limit for calculating its passive guard protection time, specifying any upper limit to the area
of exposure;
b) the overall duration of exposure under these conditions;
b) the quoted passive guard protection time including safety factor of 0,7 (see Clause D.3 for
calculation of the quoted protection time for passive laser guards);
c) the wavelength(s) for which this PEL applies;
d) the angle of incidence and (if relevant) the polarization of the incident laser radiation;
e) any minimum dimensions to the irradiated area (for example, as might apply to an active
laser guard with discrete sensor elements so that a small diameter laser beam could pass
through the guard undetected);
f) for an active laser guard, the active guard protection time.
NOTE 1 See Clause B.1 for an elaboration of terms.
NOTE 2 In all cases, a range or set of values can be stated rather than a single value.
NOTE 3 A graphical form of presentation is acceptable (for example, irradiance plotted against duration with all
other parameters constant).
5.5 Test requirements
5.5.1 General
Testing shall be performed using the complete laser guard or an appropriate sample of the
material used to construct the guard. In either case, the condition of the guard or sample shall
be such as to replicate or exceed the worst permissible physical condition of the front surface,
including reduced surface reflection and damage permitted within the scope of the routine
maintenance instructions (see 5.7).
The front surface irradiation shall be either as specified by the PEL or, in the case of sample
testing, as specified in 5.5.2.
When the front surface is subjected to the PEL exposure conditions, the accessible laser
radiation measured at the rear surface of the laser guard shall not exceed the Class 1 AEL
(tests as prescribed specified in Clause 5 of IEC 60825-1:2014). This requirement applies over
the exposure duration specified in the PEL or, in the case of an active guard, over the specified
active guard protection time measured from the moment an active guard termination signal is
issued.
NOTE In cases where materials opaque at the laser wavelength(s) are used (for example metals), the transmitted
radiation will can rise only to the Class 1 AEL when complete (or almost complete) physical removal of material along
a path through to the rear surface has been achieved. In such cases, the rise from zero transmission to a value
greatly in excess of the Class 1 AEL will therefore be rapid, and sensitive radiation detectors will not be required.
5.5.2 Sample testing
Sample guard testing shall be performed by irradiating the front surface of the guard material
using the procedure and methodology as specified in Annex D.
5.6 Labelling requirements
5.6.1 All labelling shall be placed on the rear surface of the guard.
5.6.2 The rear surface of the guard shall be clearly identified if the orientation of the guard
is important.
5.6.3 If only part of the front surface of the guard is a laser guard, this area shall be clearly
identified by a bold coloured outline and words to indicate the outer boundary of the laser guard.
5.6.4 The labelling shall state the full PEL specification.
5.6.5 The manufacturer’s name, the date and place of manufacture in accordance with
ISO 11553-1, and a statement of compliance with this document shall be provided.
5.7 User information
In addition to the specifications listed in 5.4, the following information shall be supplied to the
user by the manufacturer of a proprietary laser guard:
a) a description of the permitted uses of the laser guard;
b) a description of the form of mounting and connection of the laser guard;
c) information on the installation of the laser guard – for active laser guards this shall include
interface and supply requirements for the guard;
d) maintenance requirements, including for example details of inspection and test procedures,
cleaning, replacement or repair of damaged parts;
e) instructions that, after any actuation of the safety control system of an active guard, the
cause shall be investigated, and checks shall be made for damage, and. The instructions
shall also include the necessary remedial action to be taken before resetting the control
system;
f) the labels in 5.6 and their locations. If only part of the front surface of the guard is a laser
guard, this area shall be identified;
g) a statement of compliance with this document.
– 16 – IEC 60825-4:2022 RLV © IEC 2022
Annex A
(informative)
General guidance on the design and selection of laser guards
A.1 Design of laser guards
A.1.1 Passive laser guards
Examples of a passive laser g
...
IEC 60825-4 ®
Edition 3.0 2022-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Safety of laser products –
Part 4: Laser guards
Sécurité des appareils à laser –
Partie 4: Protecteurs pour laser
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IEC 60825-4 ®
Edition 3.0 2022-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Safety of laser products –
Part 4: Laser guards
Sécurité des appareils à laser –
Partie 4: Protecteurs pour laser
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.260 ISBN 978-2-8322-3985-8
– 2 – IEC 60825-4:2022 © IEC 2022
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Requirements for laser guards . 11
4.1 Requirement . 11
4.2 Design requirements . 12
4.3 Performance requirements . 12
4.4 Validation . 12
4.5 User information . 13
5 Proprietary laser guards . 13
5.1 General . 13
5.2 Design requirements . 13
5.3 Performance requirements . 13
5.4 Specification requirements . 14
5.5 Test requirements . 14
5.6 Labelling requirements . 14
5.7 User information . 15
Annex A (informative) General guidance on the design and selection of laser guards . 16
A.1 Design of laser guards . 16
A.2 Selection of laser guards . 16
Annex B (informative) Assessment of foreseeable exposure limit (FEL) . 18
B.1 General . 18
B.2 Reflection of laser radiation . 19
B.3 Examples of assessment conditions . 19
B.4 Exposure duration . 22
Annex C (informative) Elaboration of defined terms . 25
C.1 Distinction between FEL and PEL . 25
C.2 Active guard parameters . 25
Annex D (normative) Proprietary laser guard testing . 27
D.1 General . 27
D.2 Test conditions . 27
D.3 Protection time corresponding to the specified protective exposure limit
(PEL) . 31
D.4 Information supplied by the manufacturer. 31
Annex E (informative) Guidelines on the arrangement and installation of laser guards . 33
E.1 Overview. 33
E.2 General . 33
E.3 Risk assessment . 34
E.4 Examples of risk assessment . 36
E.5 Aids to risk assessment . 39
Annex F (informative) Guideline for assessing the suitability of laser guards . 42
F.1 Identification of hazards . 42
F.2 Risk assessment and integrity . 42
F.3 General design . 45
F.4 Selection of safeguards . 46
F.5 Guard design and construction . 46
F.6 Guard construction and materials . 48
F.7 Other safety devices . 50
F.8 Interlocking considerations . 51
F.9 Environmental considerations . 55
F.10 Installation consideration – Environmental factors – Services . 56
F.11 Maintenance and service considerations . 56
Annex G (normative) Guided beam delivery systems . 67
G.1 General . 67
G.2 General requirements . 67
G.3 Verification of safety requirements or protective measures . 69
G.4 Information for users . 69
G.5 Examples of risk assessments . 70
Bibliography . 75
Figure B.1 – Calculation of diffuse reflections . 19
Figure B.2 – Calculation of specular reflections . 19
Figure B.3 – Some examples of a foreseeable fault condition . 20
Figure B.4 – Four examples of errant laser beams that might have to be contained by a
temporary guard under service conditions . 21
Figure B.5 – Illustration of laser guard exposure during repetitive machine operation . 22
Figure B.6 – Two examples of assessed duration of exposure . 23
Figure B.7 – Assessed duration of exposure for a machine with no safety monitoring . 24
Figure C.1 – Illustration of guarding around a laser processing machine . 25
Figure C.2 – Illustration of active laser guard parameters . 26
Figure D.1 – Simplified diagram of the test arrangement . 29
Figure D.2 – Simplified diagram of the ventilation for the guard under test . 29
Figure F.1 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW CO laser . 57
Figure F.2 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser . 58
Figure F.3 – Damage resistance of 2 mm thick zinc coated steel sheet derived from 10
s exposure to a defocused beam during experiments using a CW CO laser . 58
Figure F.4 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser . 58
Figure F.5 – Damage resistance of 3 mm thick zinc coated steel sheet derived from 10
s exposure to a defocused beam during experiments using a CW CO laser . 59
Figure F.6 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser . 59
Figure F.7 – Damage resistance of 2 mm thick aluminium sheet derived from 10 s
exposure to a defocused beam during experiments using a CW CO laser . 59
Figure F.8 – Damage resistance of 2 mm thick aluminium sheet derived from 100 s
exposure to a defocused beam during experiments using a CW CO laser . 60
– 4 – IEC 60825-4:2022 © IEC 2022
Figure F.9 – Damage resistance of 1 mm thick stainless steel sheet derived from 10 s
exposure to a defocused beam during experiments using a CW CO laser . 60
Figure F.10 – Damage resistance of 1 mm thick stainless steel sheet derived from 100
s exposure to a defocused beam during experiments using a CW CO laser . 60
Figure F.11 – Damage resistance of 6 mm thick polycarbonate sheet derived from 10 s
exposure to a defocused beam during experiments using a CW CO laser . 61
Figure F.12 – Damage resistance of 6 mm thick polycarbonate sheet derived from 100
s exposure to a defocused beam during experiments using a CW CO laser . 61
Figure F.13 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 62
Figure F.14 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 62
Figure F.15 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 63
Figure F.16 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 63
Figure F.17 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 64
Figure F.18 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 64
Figure F.19 – Damage resistance of 2 mm thick aluminium sheet derived from 10 s
exposure to a defocused beam during experiments using a CW Nd:YAG laser . 65
Figure F.20 – Damage resistance of 2 mm thick aluminium sheet derived from 100 s
exposure to a defocused beam during experiments using a CW Nd:YAG laser . 65
Figure F.21 – Damage resistance of 1 mm thick stainless steel sheet derived from 10 s
exposure to a defocused beam during experiments using a CW Nd:YAG laser . 66
Figure F.22 – Damage resistance of 1 mm thick stainless steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser . 66
Table D.1 – Laser guard test classification . 30
Table F.1 – Application of ALARP . 45
Table G.1 – Beam delivery systems using free space beam delivery systems . 70
Table G.2 – Beam delivery systems using fibre optic cables . 72
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF LASER PRODUCTS –
Part 4: Laser guards
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 60825-4 has been prepared by IEC technical committee 76: Optical radiation safety and
laser equipment. It is an International Standard.
This third edition cancels and replaces the second edition published in 2006,
Amendment 1:2008 and Amendment 2:2011. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Significant amendments have been included and this edition has been prepared for user
convenience.
– 6 – IEC 60825-4:2022 © IEC 2022
The text of this International Standard is based on the following documents:
Draft Report on voting
76/704/FDIS 76/711/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it
contains colours which are considered to be useful for the correct understanding of its
contents. Users should therefore print this document using a colour printer.
INTRODUCTION
At low levels of irradiance or radiant exposure, the selection of material and thickness for
shielding against laser radiation is determined primarily by a need to provide sufficient optical
attenuation. However, at higher levels, an additional consideration is the ability of the laser
radiation to remove guard material – typically by melting, oxidation or ablation; processes that
could lead to laser radiation penetrating a normally opaque material.
IEC 60825-1 deals with basic issues concerning laser guards, including human access,
interlocking and labelling, and gives general guidance on the design of protective housings and
enclosures for high-power lasers.
Laser guards may also comply with standards for laser protective eyewear, but such compliance
is not necessarily sufficient to satisfy the requirements of this document.
Where the term "irradiance" is used, the expression "irradiance or radiant exposure, as
appropriate" is implied.
– 8 – IEC 60825-4:2022 © IEC 2022
SAFETY OF LASER PRODUCTS –
Part 4: Laser guards
1 Scope
This part of IEC 60825 specifies the requirements for laser guards, permanent and temporary
(for example for service), that enclose the process zone of a laser processing machine, and
specifications for proprietary laser guards.
This document applies to all component parts of a guard including clear (visibly transmitting)
screens and viewing windows, panels, laser curtains and walls.
In addition, this document indicates
a) how to assess and specify the protective properties of a laser guard, and
b) how to select a laser guard.
NOTE Requirements for beam path components, beam stops and those other parts of a protective housing of a
laser product which do not enclose the process zone are contained in IEC 60825-1.
This document deals with protection against laser radiation only. Hazards from secondary
radiation that may arise during material processing are not addressed.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60825-1:2014, Safety of laser products – Part 1: Equipment classification and requirements
IEC 61508 (all parts), Functional safety of electrical/electronic/programmable electronic safety-
related systems
ISO 11553-1, Safety of machinery – Laser processing machines – Laser safety requirements
ISO 12100, Safety of machinery – General principles for design – Risk assessment and risk
reduction
ISO 13849-1, Safety of machinery – Safety-related parts of control systems – Part 1: General
principles for design
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60825-1 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
access panel
panel which when removed or displaced gives human access to laser radiation
Note 1 to entry: Sheathing around a fibre, tubing used as an enclosure component or any device serving the function
of a removable or displaceable panel, can also be an "access panel" within the terms of this definition.
3.2
active guard protection time
minimum time for a given laser exposure of the front (incident) surface of an active laser guard,
measured from the issue of an active guard termination signal, for which the active laser guard
can safely prevent laser radiation accessible at its rear surface from exceeding the Class 1 AEL
3.3
active guard termination signal
signal issued by an active guard in response to an excess exposure of its front surface to laser
radiation and which is intended to lead to automatic termination of the laser radiation
Note 1 to entry: The action of a safety interlock becoming open circuit is considered a "signal" in this context.
3.4
active laser guard
laser guard which is part of a safety-related control system whereby failure of the front surface
of the laser guard triggers a termination signal
3.5
beam delivery system
system comprised of all those components, including all optical beam components and potential
beam paths and their enclosures, which when combined, transfer laser radiation emitted from
the laser radiation generator (the laser) to the workpiece
Note 1 to entry: These components may include all elements for guiding, shaping and switching the laser beam as
well as the enclosure of and support for the beam path components. See Annex G for detail on guided beam delivery
systems.
3.6
beam diameter
d
diameter of the smallest circular aperture in a plane perpendicular to the beam axis that contains
86 % of the total laser power (or energy)
Note 1 to entry: In the case of a Gaussian beam (TEM ), d corresponds to the point where the irradiance (radiant
exposure) falls to 1/e of its central peak value and the second order moments of the power density distribution
(ISO 11146-1:2005 3.2).
3.7
beam path component
optical component which lies on a defined beam path
Note 1 to entry: Examples of a beam path component include a beam steering mirror, a focus lens or a fibre optic
cable connector.
[SOURCE: IEC 60825-1:2014, 3.16, modified — Example has been removed and Note 1 to
entry has been added.]
– 10 – IEC 60825-4:2022 © IEC 2022
3.8
beam shaping component
optical component introduced in the beam path to transform the profile or cross-section of the
laser beam by means of apertures, or reflective, refractive or diffractive optical components
3.9
beam switching component
optical component or an assembly of components introduced in the beam path to direct or divert,
under external control, the beam path along predetermined direction(s) with the external control
allowing the beam path to be switched from one predetermined direction to another
3.10
fibre optic cable
optical beam guiding component that enables the transmission of laser radiation along a
transparent medium
Note 1 to entry: A fibre optic cable may have a glass or other core that carries the laser radiation and be surrounded
by cladding. The outside of the fibre is protected by cladding and may be further protected by additional layers of
other material such as a polymer or a metal to protect the fibre from mechanical deformation, the ingress of water,
etc. This term also includes other forms of transmission devices such as waveguides.
3.11
foreseeable exposure limit
FEL
maximum laser exposure on the front surface of the laser guard, within the maintenance
inspection interval, assessed under normal and reasonably foreseeable fault conditions
Note 1 to entry: The full specification of an FEL comprises different elements, including irradiance and exposure
duration. More details are given in Annex B.
3.12
front surface
face of the laser guard intended for exposure to laser radiation
3.13
laser guard
physical barrier which limits the extent of a danger zone by preventing laser radiation accessible
at its rear surface from exceeding the Class 1 AEL
3.14
laser processing machine
machine which uses a laser to process materials and is within the scope of ISO 11553-1
3.15
laser termination time
maximum time taken, from generation of an active guard termination signal, for the laser
radiation to be terminated
Note 1 to entry: Laser termination time does not refer to the response of an active laser guard but to the response
of the laser processing machine, in particular the laser safety shutter.
3.16
maintenance inspection interval
time between successive safety maintenance inspections of a laser guard
3.17
passive guard protection time
minimum time determined for a laser exposure equal to a specified protective exposure limit
(PEL) at the front (incident) surface of a passive laser guard for which the passive laser guard
can reliably prevent laser radiation accessible at its rear surface from exceeding the class 1
AEL
3.18
passive laser guard
laser guard which relies for its operation on its physical properties only
3.19
process zone
zone where the laser beam interacts with the material to be processed
3.20
proprietary laser guard
passive or active laser guard, offered by a manufacturer of laser guards as an independent
product placed on the market with a specified protective exposure limit
3.21
protective exposure limit
PEL
maximum laser exposure of the front surface of a laser guard which prevents laser radiation
accessible at its rear surface from exceeding the Class 1 AEL for the determined passive or
active guard detection time
Note 1 to entry: In practice, there may be more than one maximum laser exposure.
Note 2 to entry: Different PELs may be assigned to different regions of a laser guard if these regions are clearly
identifiable (for example, a viewing window forming an integral part of a laser guard).
Note 3 to entry: See 5.3 for the performance requirements and 5.4 for the full specification. The full specification of
a PEL comprises different elements, including irradiance and exposure duration.
3.22
rear surface
surface of a laser guard that is remote from the associated laser radiation and usually
accessible to the user
3.23
reasonably foreseeable
credible and whose likelihood of occurrence or existence cannot be
disregarded
3.24
safety maintenance inspection
documented inspection performed in accordance with manufacturer’s instructions
3.25
temporary laser guard
substitute or supplementary active or passive laser guard intended to limit the extent of the
danger zone during some service operations of the laser processing machine
4 Requirements for laser guards
4.1 Requirement
Clause 4 specifies the requirements for laser guards that enclose the process zone and are
supplied by the laser processing machine manufacturer.
– 12 – IEC 60825-4:2022 © IEC 2022
4.2 Design requirements
4.2.1 Guard requirement
A laser guard shall satisfy ISO 12100 with respect to the general requirements for guards and
also the more specific requirements with regard to its location and method of fixture. In addition,
the following specific laser requirements shall be met for a laser guard.
4.2.2 General requirements
A laser guard, in its intended location, shall not give rise to any associated hazard at or beyond
its rear surface when exposed to primary laser radiation or secondary optical radiation up to
the foreseeable exposure limit. Annex F provides guidance on assessing the suitability of laser
guards.
NOTE 1 Examples of associated hazards include high temperature, plasma, excessive ultra-violet radiation, the
release of toxic materials, fire, explosion, and electricity.
NOTE 2 See Annex B for assessment of foreseeable exposure limit.
4.2.3 Consumable parts of laser guards
Provision shall be made for the replacement of parts of a laser guard prone to damage by laser
radiation.
NOTE An example of such a part would be a sacrificial or interchangeable screen.
4.3 Performance requirements
4.3.1 General
When the front (incident) surface of a laser guard is subjected to exposure to laser radiation at
the foreseeable exposure limit, the laser guard shall prevent laser radiation accessible at its
rear surface from exceeding the Class 1 AEL at any time over the period of the maintenance
inspection interval. For automated laser processing machines intended for unattended and/or
unsupervised operation, the minimum value of the maintenance inspection interval shall be 8 h.
This requirement shall be satisfied over the intended lifetime of the laser guard under expected
conditions of operation.
NOTE 1 This requirement implies both low transmission of laser radiation and resistance to laser-induced damage.
NOTE 2 Some materials can lose their protective properties due to ageing, exposure to ultraviolet radiation, certain
gases, temperature, humidity and other environmental conditions. Additionally, some materials will transmit laser
radiation under high-intensity laser exposure, even if there is no visible damage (i.e. reversible bleaching).
4.3.2 Active laser guards
a) The active guard protection time shall exceed the laser termination time up to the
foreseeable exposure limits.
b) If an active guard detects an excessive exposure, i.e. is triggered, it shall give rise to a
visible or audible warning. A manual reset is required before laser emission can
recommence.
NOTE See Annex C for an elaboration of terms.
4.4 Validation
4.4.1 General guard validation
If the laser processing machine manufacturer chooses to make a laser guard, the manufacturer
shall confirm that the guard complies with the design requirements and can satisfy the
performance requirements set out in 4.3.
NOTE See Annex A for guidance on the design and selection of laser guards.
4.4.2 Validation of performance
4.4.2.1 The complete laser guard, or an appropriate sample of the material of construction
of the laser guard, shall be tested at each FEL identified.
It is intended that a table of predetermined PELs for common combinations of lasers and
guarding materials, together with suitable testing procedures, will be issued as an informative
annex in a future amendment to this document. This could provide a simple alternative to direct
testing for the majority of cases.
NOTE See Annex B for the assessment of FEL and Annex C for further elaboration of the terms PEL and FEL.
4.4.2.2 For testing purposes, the FEL exposure shall be achieved either:
a) by calculating or measuring the exposure and reproducing the conditions; or
b) without quantifying the FEL, by creating the machine conditions under which the FEL is
produced.
The condition of the laser guard or sample shall be such as to replicate those physical
conditions of the front surface permitted within the scope of the routine inspection instructions
and within the service life of the guard, which minimize the laser radiation protective properties
of the laser guard (for example, wear and tear and surface contamination) (see 4.5.2).
4.5 User information
4.5.1 The manufacturer shall document and provide to the user the maintenance inspection
interval for the laser guard, and details of inspection and test procedures, cleaning, replacement
or repair of damaged parts, together with any restrictions of use.
4.5.2 The manufacturer shall document and provide to the user instructions that after any
actuation of the safety control system of an active guard, the cause shall be investigated, and
checks shall be made for damage. The instructions shall also include the necessary remedial
action to be taken before resetting the control system.
5 Proprietary laser guards
5.1 General
Clause 5 specifies the requirements to be satisfied by suppliers of proprietary laser guards.
5.2 Design requirements
A proprietary laser guard shall not create any associated hazard at or beyond its rear surface
when exposed to laser radiation up to the specified PEL when used as specified in the user
information (see 5.7).
5.3 Performance requirements
The accessible laser radiation at the rear surface of the laser guard shall not exceed the
Class 1 AEL when its front surface is subjected to laser radiation at the specified PEL at least
during the passive guard protection time. For an active laser guard, this requirement shall apply
to laser radiation accessible over the period of the active guard protection time, measured from
the moment an active guard termination signal is issued.
This requirement shall be satisfied over the intended lifetime of the guard under expected
service conditions.
– 14 – IEC 60825-4:2022 © IEC 2022
5.4 Specification requirements
The full specification of a PEL shall include the following information:
a) the magnitude of irradiance or radiant exposure at the front surface of the laser guard
−2 −2
(in units of W m or J m , respectively) used to measure its passive guard protection time
and mean value and standard deviation of its tested exposure time limit for calculating its
passive guard protection time, specifying any upper limit to the area of exposure;
b) the quoted passive guard protection time including safety factor of 0,7 (see Clause D.3 for
calculation of the quoted protection time for passive laser guards);
c) the wavelength(s) for which this PEL applies;
d) the angle of incidence and (if relevant) the polarization of the incident laser radiation;
e) any minimum dimensions to the irradiated area (for example, as might apply to an active
laser guard with discrete sensor elements so that a small diameter laser beam could pass
through the guard undetected);
f) for an active laser guard, the active guard protection time.
NOTE 1 See Clause B.1 for an elaboration of terms.
NOTE 2 In all cases, a range or set of values can be stated rather than a single value.
NOTE 3 A graphical form of presentation is acceptable (for example, irradiance plotted against duration with all
other parameters constant).
5.5 Test requirements
5.5.1 General
Testing shall be performed using the complete laser guard or an appropriate sample of the
material used to construct the guard. In either case, the condition of the guard or sample shall
be such as to replicate or exceed the worst permissible physical condition of the front surface,
including reduced surface reflection and damage permitted within the scope of the routine
maintenance instructions (see 5.7).
The front surface irradiation shall be either as specified by the PEL or, in the case of sample
testing, as specified in 5.5.2.
When the front surface is subjected to the PEL exposure conditions, the accessible laser
radiation measured at the rear surface of the laser guard shall not exceed the Class 1 AEL
(tests as specified in Clause 5 of IEC 60825-1:2014). This requirement applies over the
exposure duration specified in the PEL or, in the case of an active guard, over the specified
active guard protection time measured from the moment an active guard termination signal is
issued.
NOTE In cases where materials opaque at the laser wavelength(s) are used (for example metals), the transmitted
radiation can rise only to the Class 1 AEL when complete (or almost complete) physical removal of material along a
path through to the rear surface has been achieved. In such cases, the rise from zero transmission to a value greatly
in excess of the Class 1 AEL will therefore be rapid, and sensitive radiation detectors will not be required.
5.5.2 Sample testing
Sample guard testing shall be performed by irradiating the front surface of the guard material
using the procedure and methodology as specified in Annex D.
5.6 Labelling requirements
5.6.1 All labelling shall be placed on the rear surface of the guard.
5.6.2 The rear surface of the guard shall be clearly identified if the orientation of the guard
is important.
5.6.3 If only part of the front surface of the guard is a laser guard, this area shall be clearly
identified by a bold coloured outline and words to indicate the outer boundary of the laser guard.
5.6.4 The labelling shall state the full PEL specification.
5.6.5 The manufacturer’s name, the date and place of manufacture in accordance with
ISO 11553-1, and
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