IEC 60079-29-4:2009

IEC 60079-29-4 ®
Edition 1.0 2009-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 29-4: Gas detectors – Performance requirements of open path detectors for
flammable gases
Atmosphères explosives –
Partie 29-4: Détecteurs de gaz – Exigences d’aptitude à la fonction des
détecteurs de gaz inflammables à chemin ouvert

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IEC 60079-29-4 ®
Edition 1.0 2009-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 29-4: Gas detectors – Performance requirements of open path detectors for
flammable gases
Atmosphères explosives –
Partie 29-4: Détecteurs de gaz – Exigences d’aptitude à la fonction des
détecteurs de gaz inflammables à chemin ouvert

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
V
CODE PRIX
ICS 29.260.20 ISBN 978-2-88910-049-1
– 2 – 60079-29-4 © IEC:2009
CONTENTS
FOREWORD.4
1 Scope.6
2 Normative references .7
3 Terms and definitions .7
3.1 Equipment.7
3.2 Alarms.8
3.3 Signals and indications.8
3.4 Gaseous atmospheres.8
3.5 Optical equipment .9
3.6 Performance characteristics .10
4 General requirements .11
4.1 Detection equipment .11
4.1.1 Components .11
4.1.2 Electrical assemblies and components .11
4.1.3 Optical radiation .11
4.2 Construction.11
4.2.1 General .11
4.2.2 Indicating devices.11
4.2.3 Alarm or output functions.12
4.2.4 Fault signals .12
4.2.5 Adjustments .12
4.3 Software-controlled equipment .12
4.3.1 Conversion errors.13
4.3.2 Software.13
4.3.3 Data transmission.13
4.3.4 Self-test routines .13
4.3.5 Functional concept .14
5 Test requirements .14
5.1 Introduction .14
5.2 General requirements for tests .15
5.2.1 Samples and sequence of tests .15
5.2.2 Constructional checks .15
5.2.3 Preparation of samples.15
5.2.4 Equipment for calibration and test .16
5.3 Normal conditions for test.18
5.3.1 General .18
5.3.2 Operating distance for laboratory tests .18
5.3.3 Test gases.18
5.3.4 Test gas integral concentrations .18
5.3.5 Voltage.19
5.3.6 Ambient temperature .19
5.3.7 Ambient humidity.19
5.3.8 Ambient atmosphere.19
5.3.9 Preparation of equipment .19
5.3.10 Stabilization.19
5.3.11 Communications options.20

60079-29-4 © IEC:2009 – 3 –
5.3.12 Gas detection equipment as part of systems.20
5.4 Test methods .20
5.4.1 Initial preparation and procedure .20
5.4.2 Unpowered storage .20
5.4.3 Calibration curve (not applicable to alarm only equipment with fixed
settings) .20
5.4.4 Stability .21
5.4.5 Alarm reliability.21
5.4.6 Temperature variation .22
5.4.7 Water vapour interference .23
5.4.8 Vibration.23
5.4.9 Drop test for portable and transportable equipment .24
5.4.10 Alignment .24
5.4.11 Time of response.25
5.4.12 Minimum time to operate (spot-reading equipment) .25
5.4.13 Battery capacity.25
5.4.14 Power supply variations (externally powered equipment) .26
5.4.15 Power supply interruptions and transients .27
5.4.16 Recovery from power supply interruption .27
5.4.17 Electromagnetic compatibility (EMC) .27
5.4.18 Beam block fault.28
5.4.19 Partial obscuration.28
5.4.20 Long range operation .29
5.4.21 Direct solar radiation (applicable for equipment intended for outdoor
use).29
6 Field verification equipment.30
7 Information for use .30
7.1 Labelling and marking .30
7.2 Instruction manual.30
Annex A (informative) Water vapour test apparatus .32
Bibliography.33

Figure 1 – Equipment for gas calibration and speed of response test.17
Figure A.1 – Water vapour test apparatus.32

– 4 – 60079-29-4 © IEC:2009
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 29-4: Gas detectors –
Performance requirements of open path
detectors for flammable gases
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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.
International Standard IEC 60079-29-4 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This standard supplements and modifies the general requirements of IEC 60079-0. Where a
requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of
this standard shall take precedence.
The text of this standard is based on the following documents:
FDIS Report on voting
31/819/FDIS 31/841/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.

60079-29-4 © IEC:2009 – 5 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 60079 series, under the general title: Explosives atmospheres,
can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication 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.

– 6 – 60079-29-4 © IEC:2009
EXPLOSIVE ATMOSPHERES –
Part 29-4: Gas detectors –
Performance requirements of open path
detectors for flammable gases
1 Scope
This part of IEC 60079-29 specifies performance requirements of equipment for the detection
and measuring of flammable gases or vapours in ambient air by measuring the spectral
absorption by the gases or vapours over extended optical paths, ranging typically from one
metre to a few kilometres.
Such equipment measures the integral concentration of the absorbing gas over the optical
path in units such as LFL metre for flammable gases.
NOTE 1 Actual values of concentration can be deduced only where it can be established that the concentration is
uniform over the optical path, for example in very short optical paths (<100 mm). In such cases, the equipment is
within the scope of IEC 60079-29-1.
NOTE 2 This standard is based upon present absorption techniques using infrared radiation. Other techniques
and applications may require additional test considerations (e.g. pressure test).
Equipment falling within the scope of this standard is classified by the following types:
Type 1: an optical transmitter and receiver, located at either end of a path through the
atmosphere to be monitored.
Type 2: an optical transceiver (i.e. combined transmitter and receiver) and a suitable
reflector, which may be a topographic feature or a retroreflector, located at either end of a
path through the atmosphere to be monitored.
This standard is also applicable when an equipment manufacturer makes any claims
regarding any special features of construction or superior performance that exceed the
minimum requirements of this standard. All such claims shall be verified and the test
procedures should be extended or supplemented, where necessary, to verify the claimed
performance. The additional tests shall be agreed between the manufacturer and the test
laboratory and identified and described in the test report.
This standard does not apply to any of following:
a) equipment intended to provide range resolution of gas concentration (e.g. Light direction
and ranging (LIDAR));
b) equipment consisting of a passive optical receiver without a dedicated optical source;
c) equipment intended to measure the local volumetric concentration of gas (point sensors);
d) equipment intended for the detection of dusts or mists in air;
e) equipment for cross stack monitoring;
f) equipment intended for the detection of explosives; and
g) equipment intended only for the identification of individual gas or vapour components,
(e.g. Fourier transform infrared spectroscopy (FTIR)).
This standard is applicable to equipment which is intended for use in hazardous or non-
hazardous areas, or both. Equipment for use in hazardous areas is also required to have
explosion protection (see 4.1.1).

60079-29-4 © IEC:2009 – 7 –
This standard applies to portable, transportable and fixed equipment intended for commercial
and industrial applications.
NOTE 3 This standard is intended to provide for the supply of equipment giving a level of performance suitable for
general purpose applications. However, for specific applications a prospective purchaser or an appropriate
authority may additionally require equipment to be submitted for particular tests or approval. Such tests or approval
are regarded as additional to and separate from the provisions of the standards referred to above.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079 (all parts), Explosive atmospheres
IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60079-29-1, Explosive atmospheres – Part 29-1: Gas detectors – Performance
requirements of detectors for flammable gases
IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements
IEC 61000-4-1, Electromagnetic compatibility (EMC) – Part 4-1: Testing and measurement
techniques – Overview of IEC 61000-4 series
IEC 61000-4-3, Electromagnetic compatibility (EMC) – Part 4-3: Testing and measurement
techniques – Radiated, radio-frequency, electromagnetic field immunity test
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60079-0 as well as
IEC 60079-29-1 and the following apply.
NOTE Additional definitions applicable to explosive atmospheres can be found in IEC 60050-426.
3.1 Equipment
3.1.1
alarm only equipment
equipment which generates an alarm signal but does not have a meter or output giving a
measure of the integral concentration
3.1.2
fixed equipment
equipment fastened to a support, or otherwise secured in a specific location
3.1.3
transportable equipment
equipment not intended to be carried by a person nor intended for fixed installation
3.1.4
portable equipment
equipment intended to be carried by a person
NOTE Typically portable equipment will be used as a spot-reading equipment.

– 8 – 60079-29-4 © IEC:2009
3.2 Alarms
3.2.1
alarm set point
fixed or adjustable setting of the equipment that is intended to pre-set the value of integral
concentration at which the equipment will automatically initiate an indication, alarm, or other
output function
3.2.2
alarm signal
audible, visual, electronic or other signal generated by the equipment when an integral
concentration of gas in excess of a preset value is detected
3.2.3
latching alarm
alarm which, once activated, requires a deliberate action to deactivate it
3.3 Signals and indications
3.3.1
fault signal
audible, visual, or other type of output which provides, directly or indirectly, a warning or
indication that the equipment is defective
3.3.2
beam blocked signal
audible, visual or other type of output which provides, directly or indirectly, a warning or
indication that the optical path is obscured or that the signal detected is too weak to enable
the equipment to function normally
3.3.3
inhibition signal
audible, visual, or other type of output which provides, directly or indirectly, a warning or
indication that normal operation has been suspended
3.3.4
indicating devices
means for displaying values or states in analogue or digital form
3.3.5
special state
state of the equipment other than those in which monitoring of gas concentration takes place
NOTE  For example warm-up, calibration mode or fault condition
3.4 Gaseous atmospheres
3.4.1
ambient air
atmosphere in the area being monitored by the equipment
3.4.2
clean air
air which is free from gases or vapours (flammable, toxic or environmentally harmful gases) to
which the equipment is sensitive or which influence the performance of the equipment

60079-29-4 © IEC:2009 – 9 –
3.4.3
flammable atmosphere
mixture with air, under normal atmospheric conditions, of flammable materials in the form of
gas, vapour or mist, in which, after ignition, combustion spreads throughout the unconsumed
mixture
NOTE 1 This definition specifically excludes dusts and fibres in suspension in air. Mists, though included in the
definition, are not covered by this standard.
NOTE 2 Although a mixture which has a concentration above the upper explosive limit is not a flammable
atmosphere, there is a risk of creating a flammable atmosphere by dilution.
NOTE 3 Normal atmospheric conditions include variations above and below reference levels of 101,3 kPa (1013
mbar) and 20 °C provided the variations have negligible effect on the explosion properties of the flammable
materials.
NOTE 4 For the purposes of this standard, the terms "explosive", "combustible" and "flammable" are regarded as
synonymous.
3.4.4
flammable gas
gas which, when mixed with air in certain volumetric ratios, forms a flammable atmosphere
3.4.5
integral concentration
mathematical integral of the gas concentration along the optical path.
NOTE 1  It is expressed in units of concentration multiplied by distance, e.g. LFL.metre for flammable gases or
ppm.metre for toxic gases
NOTE 2 100 % LFL x 1 metre = 1 LFL.metre;
10 % LFL × 10 metre = 1 LFL.metre.
3.4.6
lower flammable limit
LFL
volume ratio of flammable gas or vapour in air below which a flammable gas atmosphere will
not be formed
3.4.7
upper flammable limit
UFL
volume ratio of flammable gas or vapour in air above which an explosive gas atmosphere will
not be formed
3.4.8
explosion protection
measures applied in the construction of electrical equipment to prevent ignition of a
surrounding explosive gas atmosphere by the equipment
3.4.9
toxic gas
gas that may be harmful to human health and/or the performance of persons due to its
physical or physico-chemical properties
3.5 Optical equipment
3.5.1
open path
distance in space which traverses the area (or part of the area) in which the atmosphere is
being monitored and through which gases in the atmosphere are free to move

– 10 – 60079-29-4 © IEC:2009
3.5.2
optical axis
median line of the optical path
3.5.3
optical path
path traversed by optical radiation from an optical transmitter to an optical receiver.
NOTE  The radiation may traverse the open path once, twice or many times depending on the form taken by the
instrument
3.5.4
optical radiation
ultra-violet, visible or infra-red regions of the electromagnetic spectrum
3.5.5
albedo
proportion of incident light scattered back from a surface
3.5.6
transmitter
assembly in which the optical transmitting element(s) are housed and which may contain
associated optical and electrical components
3.5.7
transceiver
assembly in which the optical detecting element(s) and optical transmitting element(s) are
housed and which may contain associated optical and electrical components
3.5.8
receiver
assembly in which the optical detecting element(s) are housed and which may contain
associated optical and electrical components
3.5.9
retroreflector
individual or multiple arrangement of reflecting corners of cubes arrayed so that light is
reflected back parallel to its incident path
3.5.10
gas cell
sealed enclosure (capable of being filled with test gases) and having transparent ends
3.6 Performance characteristics
3.6.1
drift
variation with time of the indication produced by the equipment under normal conditions when
monitoring a fixed distribution of gas concentration in the optical path
3.6.2
time of response
t
x
time interval, with the equipment stabilised, between the time when an instantaneous variation
in the integral concentration is produced in the optical path and the time when the indication
reaches a stated percentage (x) of its final value

60079-29-4 © IEC:2009 – 11 –
4 General requirements
4.1 Detection equipment
4.1.1 Components
All parts of the open path gas detection equipment intended for use in explosive gas
atmospheres shall comply with the appropriate requirements for explosion protection.
The operation and storage temperature limits of this standard could exceed the required
temperature limits of these other parts of IEC 60079 series for certain types of equipment. In
this case, the examination and testing of the protection technique(s) used for the equipment
shall be extended to cover the temperature range. If this extension is not possible due to
requirements of the protection techniques used, then the temperature range of this standard
shall be reduced to the range specified for the protection technique(s).
4.1.2 Electrical assemblies and components
Electrical assemblies and components shall comply with the appropriate construction and test
requirements of 4.2 and of Clause 5 respectively.
4.1.3 Optical radiation
Optical radiation produced by the equipment shall conform to the requirements given in
IEC 60825-1.
4.2 Construction
4.2.1 General
The gas detection equipment shall be so designed and manufactured as to avoid physical
injury or other harm which might be caused by direct or indirect contact.
All parts of the equipment shall be suitable for its intended use. It shall be capable of
withstanding, without damage or impairment of performance, the effects of vibration, dust,
corrosive media and climatic conditions to be expected during operational use in
environments in which the equipment is intended to be used.
Fine adjustment of the optical beam direction shall be possible and an indication shall be
provided to confirm that satisfactory alignment of the optical beam has been achieved. Such
equipment need not form a permanent part of the equipment.
All equipment shall be constructed to facilitate, where applicable, regular functional, service,
and calibration checks.
4.2.2 Indicating devices
4.2.2.1 Indications and output signals
An indication or output signal shall be provided to show that the equipment is switched on.
The indication or output signal shall be a measure of the actual integral concentration over
the open path.
NOTE The open path is independent of the number of times the optical radiation traverses it.
If the equipment enters a special state (eg. inhibition, beam blockage or a fault), a signal shall
be provided. For fixed equipment, this shall include a contact or other transmittable output
signal. If these conditions are separately indicated, they shall be clearly identified.

– 12 – 60079-29-4 © IEC:2009
Indicating or controlling devices, where provided, need not be an integral part of the
equipment.
When the equipment is intended for alarm only, the manufacturers shall provide or identify
suitable points for connecting an indicating or recording device for testing the compliance of
the equipment with this standard.
4.2.2.2 Individual indicator lights
When individual indicator lights are incorporated in the equipment they shall be coloured as
follows:
a) alarm indicators shall be coloured RED;
b) fault, inhibition and beam blockage indicators shall be coloured YELLOW;
c) power supply indicators and normal operation indicators shall be coloured GREEN.
4.2.2.3 Indicator light marking
In addition to the colour requirements, the indicator lights shall be adequately labelled to show
their functions.
4.2.3 Alarm or output functions
When non-latching alarm devices, output contacts, or signal outputs are provided to indicate
detection of an integral gas concentration in excess of a pre-set alarm level, the fact shall be
indicated clearly and prominently in the instruction manual.
The operation of any other output functions shall be clearly stated in the manual.
4.2.4 Fault signals
Equipment shall provide a fault signal if any of the following conditions (as a minimum) occur:
a) under range indication (below the zero point) between zero and -10 % full scale
equivalent;
b) beam blockage;
c) low battery indication, if applicable;
d) a short-circuit or open-circuit in connections to any remote sensor, if applicable.
Such signals shall be differentiated from any alarms.
4.2.5 Adjustments
All means of adjustment shall be designed so as to discourage unauthorised interference with
the equipment.
Fixed explosion-protected equipment housed in explosion-protected enclosures shall be
designed so that, if any facilities for adjustment are necessary for routine re-calibration and
for resetting or like functions, these facilities shall be externally accessible. The means for
making adjustments shall not invalidate the type of protection of the equipment.
4.3 Software-controlled equipment
In the design of software-controlled equipment, the risks arising from faults in the programme
shall be taken into account.
60079-29-4 © IEC:2009 – 13 –
4.3.1 Conversion errors
The relationship between corresponding analogue and digital values shall be unambiguous.
The output range shall be capable of coping with the full range of input values within the
instrument specification. A clear indication shall result if the conversion range has been
exceeded.
The design shall take into account the maximum possible analogue-to-digital, computational
and digital-to-analogue converter errors. The combined effect of digitisation errors shall not
be greater than the smallest deviation of indication required by this standard.
4.3.2 Software
Software components shall comply with the following:
a) It shall be possible for the user to identify the installed software version, for example by
marking on the installed memory component, in (if accessible) or on the equipment or by
showing it on the display during power up or on user command.
b) It shall not be possible for the user to modify the program code.
c) Parameter settings shall be checked for validity. Invalid inputs shall be rejected. An
access barrier shall be provided against parameter changing by unauthorised persons,
e.g. it may be integrated by an authorisation code in the software or may be realised by a
mechanical lock. Parameter settings shall be preserved after removal of power, and while
traversing a special state. All user changeable parameters and their valid ranges shall be
listed in the manual.
d) Software shall have a structured design to facilitate testing and maintenance. If used,
program modules shall have a clearly defined interface to other modules.
e) Software documentation shall be included in the technical file of the product. It shall
include:
1) the equipment to which the software belongs;
2) unambiguous identification of program version;
3) functional description;
4) software structure (e.g. flow chart, Nassi-Schneidermann diagram);
5) any software modification provided with the date of change and new identification data.
4.3.3 Data transmission
Digital data transmission between spatially separated components of equipment shall be
reliable. Delays resulting from transmission errors shall not extend the response time t or
time to alarm for alarm only equipment by more than a third. If they do, the equipment shall
pass over to a defined special state. The defined special state shall be documented in the
instruction manual.
NOTE Reliability checking of the data transmission may include, but is not limited to, transmission errors,
repetition, deletions, insertion, re-sequencing, corruption, delay, and masquerade.
4.3.4 Self-test routines
Computerised digital units shall incorporate self-test routines. On failure detection, the
equipment shall pass over to a defined special state. The defined special state shall be
documented in the instruction manual.
The following minimum tests shall be performed by the equipment:
a) power supply of digital units shall be monitored within time intervals of maximum ten times
response time t or time to alarm for alarm only equipment;
– 14 – 60079-29-4 © IEC:2009
b) all available visible and audible output functions shall be tested. The test shall be carried
out automatically after starting operation or on user request. The result may need to be
verified by the user;
c) monitoring equipment with its own time base (e.g. watchdog) shall work independently and
separately from the parts of the digital unit which perform the data processing. If a failure
is detected by the monitoring equipment the equipment shall enter into a special state;
d) program and parameter memory shall be monitored by procedures which allow the
detection of a single bit error;
e) volatile memory shall be monitored by procedures that test the readability and writeability
of the memory cells.
The tests except for test b) shall be done automatically and be repeated cyclically equal to or
less than 24 h and after switching on.
4.3.5 Functional concept
Functional concept analysis and evaluation depend on the documentation from the
manufacturer. The verification shall be performed by using the following list:
– measuring sequence (including all possible variations);
– possible special states;
– parameters and their tolerable adjustment range;
– representation of measuring values and indications;
– generation of alarms and signals;
– extent and realisation of test routines;
– extent and realisation of remote data transmission.
5 Test requirements
5.1 Introduction
The general requirements for test, conditions for test and test methods presented in 5.2, 5.3
and 5.4 respectively are intended as a basis for establishing whether the equipment conforms
to the particular performance requirements specified in subsequent parts of this standard.
This standard is also applicable when an equipment manufacturer makes any claims
regarding any special features of construction or superior performance that exceed the
minimum requirements of this standard. This may be increased accuracy or performance
within the limits of the standard, or performance beyond the specifications of the standard. All
such claims, including environmental claims, shall be verified and the test procedures shall be
extended or supplemented, where necessary, to verify the claimed performance.
NOTE 1 Any additional tests should be agreed between the manufacturer and the test laboratory, and identified
and described in the test report.
NOTE 2 A manufacturer IP rating claim may not necessarily imply that the equipment will perform under the test
conditions of the IP rating. Any performance claims as to dust or particulate water would have to be separately
verified by test.
When claiming a superior performance outside these specifications, the measurement
accuracy is not required to meet the standard’s minimum requirements when outside this
specification (e.g. for the normal temperature range of –25 °C to +55 °C the accuracy shall be
±10 % of the measuring range, but an extended temperature range of –40 °C to –25 °C may
have a wider tolerance, such as ±15 % of the measuring range).

60079-29-4 © IEC:2009 – 15 –
5.2 General requirements for tests
5.2.1 Samples and sequence of tests
For the purposes of type-testing, the tests shall be carried out on one sample equipment
except that an additional sample equipment may be used for long term stability tests.
The equipment shall be subjected to all of the tests applicable to that type of equipment, as
described in 5.4. Tests are grouped in the following list but the sequence in which the tests
are undertaken shall be agreed between the test authority and the manufacturer.
a) Initial preparation and procedure (5.4.1)
b) Unpowered storage (5.4.2)
c) Preparation and alarm checks
– Calibration curve (5.4.3)
– Alarm reliability (5.4.5)
– Time of response (5.4.11)
– Minimum time to operate (5.4.12)
– Field verification equipment (Clause 6)
d) Stability (5.4.4)
e) Environmental tests
– Temperature variation (5.4.6)
– Water vapour interference (5.4.7)
– Direct solar radiation (5.4.21)
f) Optical beam tests
– Alignment (5.4.10)
– Beam block fault (5.4.18)
– Partial obscuration (5.4.19)
– Long range operation (5.4.20)
g) Electrical tests
– Battery capacity (5.4.13)
– Power supply variations (5.4.14)
– Power supply interruptions and transients (5.4.15)
– Recovery from power supply interruptions (5.4.16)
– Electromagnetic compatibility (EMC) (5.4.17)
h) Mechanical tests
– Vibration (5.4.8)
– Drop test for portable and transportable equipment (5.4.9)
5.2.2 Constructional checks
Equipment shall be checked to ensure that the constructional requirements of 4.2 are
satisfied.
5.2.3 Preparation of samples
The sample equipment shall, as nearly as possible, be prepared and mounted as for typical
service using the manufacturer's brackets and fittings, including all necessary
interconnections and initial adjustments, and in accordance with the manufacturer's written
instructions.
– 16 – 60079-29-4 © IEC:2009
For Type 2 equipment designed for use with a natural topographical feature, such as a
reflector, that feature shall be represented by a plane diffusing surface set normal to the
optical axis of the measured volume.
The surface shall be large enough in extent to intercept the whole of the measured volume
and its albedo shall lie between 0,1 and 0,3 over the wavelength range employed by the
equipment.
For equipment without an indication of measurement, for example, in alarm only equipment,
the output of equipment from a test point sh
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