The measured values of the integral concentration for each gas shall not differ from the nominal values by more than ±10 % of the measuring range or ±20 % of the measured value, whicheve
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.
Alarms
The alarm set point is a predetermined or adjustable setting on the equipment that defines the integral concentration value at which the system will automatically trigger an indication, alarm, or other output functions.
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
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
A beam blocked signal is an audible, visual, or alternative output that serves as a warning or indication It alerts users when the optical path is obstructed or when the detected signal is insufficient for the equipment to operate 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
Gaseous atmospheres
3.4.1 ambient air atmosphere in the area being monitored by the equipment
Clean air refers to air that is devoid of gases or vapors, including flammable, toxic, or environmentally harmful substances, which could affect the sensitivity and performance of equipment.
A flammable atmosphere is created when a mixture of flammable materials, such as gas, vapor, or mist, combines with air under normal atmospheric conditions In this environment, once ignition occurs, combustion can rapidly spread 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;
LFL volume ratio of flammable gas or vapour in air below which a flammable gas atmosphere will not be formed
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
Optical equipment
The open path distance in space refers to the area being monitored in the atmosphere, allowing for the free movement of gases.
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
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
The response time, denoted as \( t_x \), refers to the time interval during which the equipment stabilizes after an instantaneous change in the integral concentration occurs in the optical path This interval is measured from the moment of the concentration change to when the indication reaches a specified percentage (x) of its final value.
Detection equipment
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 temperature limits for operation and storage in this standard may surpass those specified in other parts of the IEC 60079 series for certain equipment types Consequently, the examination and testing of the protection techniques employed must encompass the broader temperature range If extending this range is unfeasible due to the protection techniques' requirements, the temperature range of this standard must be adjusted to align with the limits set for those techniques.
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.
Optical radiation
Optical radiation produced by the equipment shall conform to the requirements given in IEC 60825-1.
Construction
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 components of the equipment must be appropriate for their intended purpose, ensuring they can endure the impacts of vibration, dust, corrosive substances, and environmental conditions expected during operational use.
The optical beam direction can be finely adjusted, with an indication provided to confirm proper alignment This equipment does not need to be a permanent fixture.
All equipment shall be constructed to facilitate, where applicable, regular functional, service, and calibration checks.
Indicating devices
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
In the event that the equipment enters a special state, such as inhibition, beam blockage, or a fault, a signal must be generated For fixed equipment, this includes a contact or another form of transmittable output signal Additionally, if these conditions are indicated separately, they should be clearly labeled for easy identification.
Indicating or controlling devices, where provided, need not be an integral part of the equipment
Manufacturers must provide or identify appropriate connection points for an indicating or recording device when the equipment is designed solely for alarm purposes, ensuring compliance with the relevant standards.
In equipment design, individual indicator lights should follow a specific color coding: alarm indicators must be RED, fault, inhibition, and beam blockage indicators should be YELLOW, while power supply and normal operation indicators are designated as GREEN.
In addition to the colour requirements, the indicator lights shall be adequately labelled to show their functions.
Alarm or output functions
Non-latching alarm devices must clearly indicate in the instruction manual when they detect gas concentrations exceeding a pre-set alarm level through their output contacts or signal outputs.
The operation of any other output functions shall be clearly stated in the manual.
Fault signals
Equipment must generate a fault signal under specific conditions, including: a) under range indication (below zero) between zero and -10% of full scale; b) beam blockage; c) low battery indication, if applicable; and d) short-circuit or open-circuit in connections to any remote sensor, if applicable.
Such signals shall be differentiated from any alarms.
Adjustments
All means of adjustment shall be designed so as to discourage unauthorised interference with the equipment
Explosion-protected equipment within explosion-proof enclosures must be designed for easy external access to adjustment facilities required for routine recalibration and resetting It is essential that these adjustment means do not compromise the equipment's protective features.
Software-controlled equipment
Conversion errors
The relationship between analogue and digital values must be clear and unambiguous The output range should accommodate the complete spectrum of input values specified for the instrument, and there should be a distinct indication if the conversion range is surpassed.
The design must consider the maximum potential errors from analogue-to-digital, computational, and digital-to-analogue converters The total impact of digitisation errors should not exceed the minimum indication deviation specified by this standard.
Software
Software components must adhere to specific requirements: users should be able to identify the installed software version through markings on the memory component or display during startup Users must not have the ability to modify the program code, and parameter settings must be validated, rejecting any invalid inputs Access barriers, such as authorization codes or mechanical locks, should prevent unauthorized changes to parameters, which must be preserved even after power loss All user-adjustable parameters and their valid ranges should be documented in the manual Additionally, software should be designed with a structured approach to support testing and maintenance, with clearly defined interfaces for program modules Comprehensive software documentation must be included in the product's technical file.
1) the equipment to which the software belongs;
2) unambiguous identification of program version;
4) software structure (e.g flow chart, Nassi-Schneidermann diagram);
5) any software modification provided with the date of change and new identification data.
Data transmission
Reliable digital data transmission is essential for equipment components that are spatially separated Any delays caused by transmission errors must not increase the response time \( t_{90} \) or the alarm time for alarm-only equipment by more than one-third If such delays occur, the equipment must transition to a specified special state, which should be clearly 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.
Self-test routines
Computerized digital units will include self-test routines, and upon detecting a failure, the equipment will transition to a specified special state, which will be detailed in the instruction manual.
The equipment must undergo several essential tests: a) the power supply of digital units should be monitored at intervals not exceeding ten times the response time \( t_{90} \) or the alarm time for alarm-only equipment; b) all visible and audible output functions must be tested automatically upon operation start or user request, with results subject to user verification; c) monitoring equipment with its own time base, such as a watchdog, must operate independently from the digital unit's data processing components, entering a special state upon failure detection; d) program and parameter memory should be monitored to detect single bit errors; e) volatile memory must be tested for readability and writeability of 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.
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);
– 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
Introduction
The requirements and methods outlined in sections 5.2, 5.3, and 5.4 serve as a foundation for assessing whether the equipment meets the specific performance criteria defined in later sections of this standard.
This standard applies when equipment manufacturers assert special construction features or superior performance that surpass the minimum requirements Claims of increased accuracy or performance, whether within or beyond the standard's specifications, must be verified Additionally, all claims, including those related to environmental impact, require validation, and testing procedures should be enhanced as needed to confirm the asserted performance.
NOTE 1 Any additional tests should be agreed between the manufacturer and the test laboratory, and identified and described in the test report
A manufacturer's IP rating claim does not guarantee that the equipment will function as expected under the specified test conditions Any assertions regarding its performance against dust or water must be independently verified through testing.
When asserting enhanced performance beyond specified limits, measurement accuracy does not need to adhere to the standard's minimum criteria For instance, within the normal temperature range of –25 °C to +55 °C, the accuracy must be ±10 % of the measuring range; however, in an extended temperature range of –40 °C to –25 °C, a broader tolerance of ±15 % of the measuring range may be acceptable.
General requirements for tests
Samples and sequence of tests
Type-testing will be conducted on a single sample of equipment, although an additional sample may be utilized for long-term stability assessments.
All equipment must undergo the relevant tests as outlined in section 5.4, with the specific sequence of tests to be determined collaboratively by the test authority and the manufacturer The tests include initial preparation and procedure (5.4.1), unpowered storage (5.4.2), and preparation and alarm checks.
– Field verification equipment (Clause 6) d) Stability (5.4.4) e) Environmental tests
– Direct solar radiation (5.4.21) f) Optical beam tests
– Long range operation (5.4.20) g) Electrical tests
– 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
– Drop test for portable and transportable equipment (5.4.9)
Constructional checks
Equipment shall be checked to ensure that the constructional requirements of 4.2 are satisfied.
Preparation of samples
The sample equipment must be set up and installed in a manner that closely resembles typical service conditions, utilizing the manufacturer's brackets and fittings This includes all essential interconnections and initial adjustments, following the manufacturer's written guidelines.
Type 2 equipment intended for use with natural topographical features, like reflectors, must incorporate a plane diffusing surface aligned perpendicular to the optical axis of the measured volume.
The surface must be sufficiently large to capture the entire measured volume, with an albedo ranging from 0.1 to 0.3 across the wavelengths used by the equipment.
For equipment without an indication of measurement, for example, in alarm only equipment, the output of equipment from a test point shall be connected to a continuously recording output display device.
Equipment for calibration and test
The test facility must be designed to allow for quick changes of the test gas in individual cells, ensuring that equipment, as illustrated in Figure 1, can facilitate rapid cell exchanges This design prevents transient obscuration from walls or window retaining structures, avoiding any "beam blocked" conditions Additionally, the transverse dimensions of the cells should be sufficiently large to prevent any partial blockage of the beam.
NOTE 1 The test described in 5.4.8 and 5.4.21 may require cells of large dimensions or the use of an alternate gas simulation filter
Cells should be positioned near the receiving aperture of the equipment to reduce the impact of reflections on the receiver and to prevent any partial obstruction of the beam.
To optimize measurement accuracy, the selection of window characteristics—such as material, thickness, and flatness—as well as their inclination is crucial in reducing reflection, distortion, and beam attenuation across the effective bandwidth of the measuring radiation Additionally, any signal errors due to wavelength-dependent attenuation in the window material must be accounted for within the measurement tolerance for the specific test.
The axial length of the cells can be adjusted based on the gas concentration within them, ensuring standard integral gas concentration values for calibration purposes.
Cells can be filled with various test gases, such as clean air for zero calibration and the specific gas to be measured It is essential that cells used for zero setting have a minimal impact on equipment calibration The difference in readings between ambient air and a gas cell filled with clean air should not exceed ±2% of the measuring range.
Heating may be applied to cells to ensure that vapour, condensable at room temperature, can be maintained in the gaseous state
NOTE 2 To avoid using large volumes of flammable gas and air mixtures, cells of appropriate length filled with test gas of substantially less than 100 % LFL may be used for small path integral concentrations, (e.g 0,5 LFL × 1 m), and either 100 % V/V flammable gas or mixtures of flammable and inert gas may be used for larger integral concentrations
In the water vapor interference test 5.4.7, a 2-meter-long cell is required to hold water vapor at a partial pressure of 50 kPa To avoid condensation, it is essential to heat the cell walls and windows to a suitable temperature.
Gas cells designed for testing flammable gases must be built to ensure that measurement errors due to wavelength attenuation variations in the cell windows are limited to less than 2% of the measuring range or 5% of the measured value, whichever is greater.
Standard gas cells which may be alternately rotated into the axis of the measuring beam
Transceiver used with retroreflector or receiver used with a transmitter
Figure 1 – Equipment for gas calibration and speed of response test
Fog, precipitation, and dust can significantly attenuate the optical path, along with any material deposited on optical surfaces To simulate this effect, an opaque grid mask should be placed within 100 mm of the equipment's receiving aperture.
The mask must feature a mesh design with matte black surfaces, specifically configured to transmit (10 ± 1) % of the incident beam for the tests outlined in section 5.4.16 The mesh spacing should be significantly smaller than the receiving aperture of the equipment while being larger than the wavelength of the measuring radiation For equipment operating at a single wavelength, a filter can be utilized to achieve equivalent attenuation.
For equipment that uses coherent light sources, the mask shall be chosen such that it does not create interference The manufacturer may provide an appropriate attenuator
If the equipment is sensitive to changes in temperature, the temperature shall be recorded within ±2 °C and the results corrected as appropriate
To evaluate the equipment's response to controlled beam blocking, a large opaque shutter with matte black absorbing surfaces and a straight leading edge must be used This shutter should move across the measuring radiation at a consistent speed of about 10 mm/s until the beam is fully obstructed, and then it should reverse at the same speed to completely withdraw the shutter.
For the test described in 5.4.18.2, the facility for driving at 10 cm/s is not required
For temperature variation tests, components such as transmitters, receivers, transceivers, reflectors, or control units can be positioned in environmental chambers equipped with a window or aperture, allowing the equipment to operate with an optical path that remains primarily outside the chambers.
Windows should be designed and aligned with the optical axis of the equipment to reduce reflection distortion and minimize beam attenuation across the effective bandwidth of the measuring radiation.
The environmental chamber must allow for precise control of temperature and humidity within the specific ranges needed for each test It is essential to manage these conditions effectively to prevent condensation on windows during testing.
Calibrations and tests can utilize a front metallised plane mirror to efficiently fold the beam path and reduce space requirements It is essential to select the mirror's characteristics, such as material and flatness, to minimize distortion and attenuation of the beam across the effective bandwidth of the measuring radiation Additionally, the signal strength variation due to the mirror's introduction should not exceed 5%.
Normal conditions for test
General
The test conditions specified in 5.3.2 to 5.3.12 shall be used for all tests unless otherwise stated.
Operating distance for laboratory tests
The distance for all tests between the source and receiver, or between the transceiver and reflector, must be between 5 m and 20 m, or the maximum shorter distance For equipment with a minimum operating distance exceeding 20 m, an attenuator can be utilized to decrease beam intensity, or the operating distance should be mutually agreed upon by the manufacturer and the test laboratory.
Test gases
The testing procedure requires the use of a standard test gas, with calibration curves evaluated for all other gases claimed to meet the standard The standard test gas should be selected from the range of gases where the equipment exhibits minimum sensitivity, typically methane or ethylene for infrared detectors.
Test gas integral concentrations
The standard test gas is the specific gas or vapor for which the equipment's compliance with this standard is asserted Its concentration in the selected cell must ensure an integral concentration that corresponds to a value near the midpoint of the equipment's measurement range, with an accuracy of ±5% of the nominal value.
Calibration of standard path integral concentration values is essential for ensuring alarm reliability, as outlined in sections 5.4.3 and 5.4.5 These values are specific to the measuring range and alarm settings of each instrument It is crucial that the integral concentration for each gas is accurate within ±5% of the nominal value.
NOTE The gas mixture may be prepared by any suitable method, e.g in accordance with the methods outlined in
Voltage
Mains powered equipment shall be operated at the nominal supply voltage, ±2 % and frequency, except for tests requiring voltage changes, as 5.4.14 and 5.4.15
D.C powered equipment shall be operated at the manufacturer's recommended supply voltage, ±2 % except for the over-voltage and under-voltage test of 5.4.14 and 5.4.15.3
For short-term tests, battery-operated equipment must be equipped with fresh or fully charged batteries at the start of each test series In contrast, long-term testing allows the use of a stabilized power supply to energize the equipment.
Ambient temperature
The ambient air temperature must remain constant within ±2 °C, specifically between 15 °C and 25 °C, for the duration of each test, with exceptions for the unpowered storage test, long-term drift test, temperature variation test, long-range operation test, and direct solar radiation test.
Ambient humidity
All tests, except for the unpowered storage test, long-term drift test, temperature variation test, and water vapor interference test, will be conducted in ambient air with a relative humidity ranging from 20%.
80 % throughout the duration of each test.
Ambient atmosphere
During testing, the ambient atmospheric pressure in the optical path outside the test cell must be maintained between 86 kPa and 108 kPa, and the composition of the ambient atmosphere must meet the specifications outlined in the subsequent sections of this standard.
The test setup shall ensure that the ambient atmosphere remains uniform over the entire optical path and does not significantly influence the measured value.
Preparation of equipment
Before starting any test, it is essential to prepare the equipment according to the manufacturer's guidelines However, once the test is in progress, no further adjustments should be made unless explicitly allowed by the specific test procedure.
Stabilization
In the tests outlined in section 5.4, it is essential to allow the equipment to stabilize under new test conditions before taking measurements for comparison.
Equipment shall be considered to be stabilised when three successive measurements of a fixed concentration of gas taken at 5 × t 90 of the equipment indicate no changes greater than
Communications options
For gas detection equipment with serial or parallel communication options, it is essential to conduct tests outlined in sections 5.4.3, 5.4.6, and 5.4.11 with all communication ports connected Ensure that the maximum transaction rate, cabling specifications, and activity levels recommended by the manufacturer are utilized during these tests.
Gas detection equipment as part of systems
Gas detection equipment integrated into systems must undergo tests specified in sections 5.4.3, 5.4.6, 5.4.11, and 5.4.14 These tests should be conducted at the maximum system communications transaction rate and activity level, reflecting the most extensive and intricate system configuration allowed by the manufacturer.
Test methods
Initial preparation and procedure
The equipment must be powered on and verified for proper functionality using clean air and a mid-range concentration of standard test gas, as specified in sections 5.3.4.1 and 5.3.3, with gas cells being inserted sequentially into the beam.
Adjustments shall, if needed, be carried out to obtain correct readings in accordance with the manufacturer's instructions
The equipment shall be calibrated using the manufacturer’s calibration fixture and the specified calibration procedures.
Unpowered storage
All equipment components must undergo sequential exposure to specific conditions in clean air This includes a temperature of (-25 ± 2) °C for a minimum of 24 hours, followed by (20 ± 5) °C for at least 24 hours, then (60 ± 2) °C for a duration of 24 hours, and finally returning to (20 ± 5) °C for another 24 hours.
The parts of the equipment shall then be subjected to the appropriate test methods given in 5.4.3 to 5.4.21.
Calibration curve (not applicable to alarm only equipment with fixed settings)
The equipment must be calibrated for each gas specified by the manufacturer, ensuring compliance with the relevant standards as outlined in section 7.2 f) 1).
The equipment shall be exposed for each gas to 10 % of range and three selected values of path integral concentration evenly spread over the measurement range (for example, 25 %,
50 % and 75 % of range) or, in the case of alarm instruments with adjustable set points, over the range covered by the alarms Equipment as described in 5.2.4.1 shall be used
Measurements will be conducted using a cell or multiple cells filled with the chosen concentration of calibration gas, starting from the lowest value and progressing to the highest This procedure will be repeated three times for each gas.
The integral concentration measurements for each gas must remain within ±10% of the measuring range or ±20% of the measured value, depending on which is greater.
NOTE Where the equipment is not fitted with a meter or other data display, readings may be taken using an external display connected to a suitable test point (see 5.2.3).
Stability
5.4.4.1 Slow increase of gas volume ratio (Equipment with automatic drift compensation only)
Allow the equipment to warm up for one hour in clean air before testing Introduce test gas at a volume ratio of 1% of the measuring range for 15 minutes Gradually increase the test gas volume ratio by 1% every 15 minutes until reaching a final volume of 10% of the measuring range Ensure that the deviation of the readings during the test remains below 5% of the measuring range.
5.4.4.2 Long-term stability (continuous-duty a.c or d.c powered)
The equipment will be tested in ambient air over a duration of 8 weeks During this period, a cell containing test gas to achieve the standard mid-range integral concentration, as specified in section 5.3.4.1, will be introduced into the optical path for 3 minutes at approximately one-week intervals and at the conclusion of the test, with readings documented accordingly.
The integral concentration measurements for each gas must not deviate from the nominal values by more than ±10% of the measuring range or ±20% of the measured value, depending on which is greater.
5.4.4.3 Long-term stability (continuous-duty battery powered)
The equipment must operate in clean air for 8 hours each working day over a span of 20 days During each operating period, the equipment will be exposed to the standard test gas until stabilization occurs Measurements will be recorded before the application of the gas, after stabilization, and before the gas is removed.
The integral concentration measurements for each gas must not deviate from the nominal values by more than ±10% of the measuring range or ±20% of the measured value, depending on which is greater.
5.4.4.4 Stability (spot-reading equipment only)
The equipment shall be exposed to clean air for 1 min followed by the standard test gas for
1 min The operation shall be repeated 200 times within an 8 h period A reading shall be recorded at the conclusion of each operation
The integral concentration measurements for each gas must not deviate from the nominal values by more than ±10% of the measuring range or ±20% of the measured value, depending on which is greater.
NOTE For these tests, battery-powered equipment should be powered from internal batteries wherever possible, otherwise an external power supply may be used.
Alarm reliability
The alarm shall operate during every cycle of the test in 5.4.5.2 or 5.4.5.3 If a latching alarm is provided, the operation and manual reset action shall be checked during every cycle
Equipment with single or multiple pre-set alarms must undergo testing for each alarm setting by introducing a test gas cell into the optical path Each test cell should contain a concentration of 120% of the nominal value corresponding to the specific alarm set point.
The test gas exposure time must be at least double the t 90 response time of the equipment, followed by an equal duration of exposure to clean air.
The procedure shall be repeated five times The alarm shall be reset automatically or manually, as applicable on each exposure to clean air
The alarm set points should be configured to function within the mid-band range, specifically between 40% and 60% of the total span Following this adjustment, the test procedure outlined in section 5.4.5.2 must be implemented.
Temperature variation
The equipment must be tested in a temperature chamber that maintains specified temperatures within ±2 °C Once the equipment reaches the designated temperature, it should be exposed to clean air and standard test gas for a minimum of 3 hours or until stabilized within ±2 °C for at least 1 hour If temperature compensation is present, the gas cell must match the equipment's temperature; otherwise, it should be outside the chamber Testing involves placing the energized transmitter or transceiver in the chamber while the reflector or receiver remains at room temperature, with tests conducted at –25 °C, +20 °C, and +55 °C Alternatively, both transmitter and receiver can be tested together in the chamber, utilizing signal attenuation or mirrors if needed Following these tests, the energized transmitter is placed in the chamber while the receiver is at room temperature, with additional tests at room temperature plus and minus 20 K Finally, the receiver is placed in the chamber, and the transmitter is at room temperature for further testing.
When testing equipment, it is essential to consider various temperature conditions For indicators or control units that are typically installed separately from the transmitter and receiver, testing should occur at +5 °C, +20 °C, and +55 °C, while ensuring the transmitter and receiver remain at +20 °C Additionally, for battery-operated devices, they must be placed in a temperature chamber and operated normally after a stabilization period, with the reflector maintained at room temperature Testing for these devices should be conducted at –10 °C, +20 °C, and +40 °C.
The measured value at +20 °C must maintain its function without loss, and any deviation from this value should not exceed ±10% of the measuring range or ±20% of the measured value, depending on which is greater.
Water vapour interference
Cells, as outlined in section 5.2.4.1, should be filled to atmospheric pressure with dry, clean air and water vapor at a partial pressure of 50 kPa, and then introduced sequentially into the optical beam path.
For equipment incorporating alarms only, the alarm shall not be actuated by a test gas of
14 % to 16 % of full-scale concentration and be actuated by a test gas of 24 % to 26 % of full- scale concentration while exposed to both humidity extremes
The integral concentration measurements for each gas must not deviate from the nominal values by more than ±10% of the full-scale gas concentration or ±20% of the initial measured value, depending on which is greater.
NOTE 1 Care should be taken to prevent moisture from collecting on the windows of the cell
NOTE 2 Annex A provides an example test setup.
Vibration
The vibration test machine must include a vibrating table that can generate vibrations with adjustable frequency and peak acceleration, ensuring that the test equipment is securely mounted according to the specified test procedures.
The transmitter and receiver or transceiver shall be individually vibrated in clean air in each of three planes parallel to each of the three major axes of the equipment
The alarm set point shall be set to 20 % of full-scale range
Before and at the conclusion of the test the equipment shall be exposed to clean air followed by the mid-range signal condition
The equipment must be installed on the vibration table as it would be during actual service use, incorporating any standard resilient mounts, carriers, or holding devices included with the equipment.
The equipment must undergo vibration testing across the specified frequency range at the designated excursion or constant acceleration peak for one hour in each of the three mutually perpendicular planes The frequency should change at a rate of 10 Hz/min, with a tolerance of ± 2 Hz/min.
For portable and transportable equipment, remote sensors, and controllers where the sensor is integral with or directly attached to the controller, the vibration shall be as follows:
– 10 Hz to 30 Hz, 1,0 mm total excursion;
– 30 Hz to 150 Hz, 19,6 m/s 2 acceleration peak
For control units intended to be installed remotely from the sensor, the vibration shall be as follows:
– 10 Hz to 30 Hz, 1,0 mm total excursion;
– 30 Hz to 100 Hz, 19,6 m/s 2 acceleration peak
The equipment must maintain full functionality without experiencing false alarms, fault signals, or hazards Additionally, the integral concentration measurements for each gas should not deviate from the nominal values by more than ±10% of the measuring range or ±20% of the measured value, whichever is greater.
Drop test for portable and transportable equipment
This test is specifically designed for portable and transportable equipment If the manufacturer advises using the instrument within its carrying case, the test must be conducted with the case included.
If the instruction manual indicates that components of fixed equipment can function as portable or transportable equipment, they should be treated as such for testing purposes.
Before and at the conclusion of the test the equipment shall be exposed to clean air followed by the standard test gas
Portable equipment shall be released, while operating, from a height of 1 m above a concrete surface and allowed to free fall
Transportable equipment with a mass less than 5 kg shall be released, while not operating, from a height of 0,3 m above a concrete surface and allowed to free fall
Other transportable equipment shall be released, while not operating, from a height of 0,1 m above a concrete surface and allowed to free fall
The test must be conducted three times, with the portable equipment released each time on a different surface facing down, while the transportable equipment should be positioned in its normal transport orientation.
The equipment fails the test if there is any loss of function, such as alarms, controls, or displays Additionally, false alarms, fault signals, or any damage that poses a hazard must be avoided The integral concentration measurements for each gas must not deviate from the nominal values by more than ±10% of the measuring range or ±20% of the measured value, whichever is greater.
Alignment
After preparing the equipment and calibrating it for the specific gas, a gas cell with standard test gas is placed in the beam, and the integral concentration of the gas is recorded.
To ensure accurate gas concentration readings, the receiver or transceiver must be tilted around two orthogonal axes, perpendicular to the beam axis, while the transmitter or reflector remains in its optimal position This adjustment should be made up to the maximum stability limit specified by the manufacturer, and the integral concentration of gas should be recorded for each position.
After restoring the receiver or transceiver to its optimal position, the transmitter or reflector should be tilted along two orthogonal axes that are perpendicular to the beam axis, reaching the maximum stability limit specified by the manufacturer (7.2 c) The integral concentration of gas must be recorded for each adjustment.
The equipment must avoid generating false alarms, and the integral concentration measurements for each gas should not deviate from the nominal values by more than ±10% of the measuring range or ±20% of the measured value, whichever is greater.
Time of response
Using test equipment designed and operated in accordance with 5.2.4, a cell containing mid- range integral concentration, as 5.3.4.1, of standard test gas, as 5.3.3 shall be rapidly inserted into the optical path
The time (t 90 ) taken to reach 90 % of the final reading of the standard test gas path integral concentration shall be recorded
A measured value of 90 % of the final value shall be achieved in a time not exceeding 10 s
The process will be repeated, but this time the test gas cell will be quickly replaced with a clean air cell of identical dimensions The time taken for the signal to decrease to 10% of the initial test gas reading will be documented.
A measured value shall indicate 10 % of the previous final value in a time not exceeding 10 s
Test equipment compliant with section 5.2.4 is utilized to expose a cell containing test gas at an integral concentration of (120 ± 10) % of the alarm set point concentration to the optical path The time taken from the step change to the activation of the alarm is then recorded.
The procedure shall be repeated for other fixed alarm settings
For equipment with adjustable alarms, the set points shall be adjusted to operate in the mid- band, approximately 40 % to 60 % of the span, of the range of settings
Following the positive step-change in integral concentration, the time taken to alarm shall not exceed 10 s.
Minimum time to operate (spot-reading equipment)
The standard test gas cell shall be inserted into the optical path and the measurement procedure shall be initiated
The standard test gas cell shall then be removed from the optical path and the measurement procedure shall be initiated
A 90 % of the change in reading in both directions shall be reached in less than 30 s.
Battery capacity
5.4.13.1 Battery-powered portable continuous duty equipment
The battery shall be fully charged at the beginning of the test Initial readings shall be taken in clean air and with the standard test gas
The equipment must be operated in clean air for a total duration of 8 hours if it has a user-operable on/off switch, 10 hours if it does not, or for any extended period as specified by the manufacturer.
At the conclusion of the designated period, the equipment is subjected to clean air followed by the standard test gas The integral concentration measurements for each gas must not deviate from the initial values by more than ±5% of the measuring range or ±10% of the measured value, whichever is greater.
The equipment will operate in clean air until a low battery condition is indicated, after which it will continue functioning for an additional period.
After a 10-minute period, a clean air reading and a standard test gas reading will be recorded The integral concentration measurements for each gas must not deviate from the initial values by more than ±10% of the measuring range or ±20% of the measured value, whichever is greater.
5.4.13.2 Battery-powered portable spot-reading equipment
The battery shall be fully charged at the beginning of the test Initial readings shall be taken in clean air and with the standard test gas
The equipment will be operated in clean air for a total of 200 cycles, with each operation lasting a minimum of one minute A one-minute interval will follow each operation.
After completing 200 operations, the equipment is subjected to clean air followed by the standard test gas The integral concentration measurements for each gas must not deviate from the initial values by more than ±5% of the measuring range or ±10% of the measured value, whichever is greater.
The operations will continue in clean air until a low battery condition is indicated The equipment will then be operated for an additional period.
After conducting the test 10 times, a clean air reading and a standard test gas reading will be recorded The integral concentration values for each gas must not deviate from the initial values by more than ±10% of the measuring range or ±20% of the measured value, whichever is greater.
Power supply variations (externally powered equipment)
The equipment must be installed under standard conditions, adhering to the nominal supply voltage and, if applicable, the rated frequency Subsequently, it will undergo a series of tests conducted under mid-range concentration conditions.
The equipment calibration shall be checked at both 115 % and 80 % of nominal supply voltage
When a manufacturer specifies a supply voltage range that differs from the standard, the equipment must be tested at both the upper and lower limits of the voltage range provided by the manufacturer.
It shall be verified at the minimum supply voltage that all output functions are working properly even at the maximum load conditions
NOTE 1 This includes testing of analogue outputs at the maximum load and maximum current
NOTE 2 This includes testing that relays are able to energise at the minimum supply voltage
Any deviation of the measured value from the nominal supply voltage must not exceed ±5% of the measuring range or ±10% of the measured value, depending on which is greater.
Power supply interruptions and transients
Adjustable alarm equipment shall be set so that the lowest alarm level is 20 % of the calibrated measuring range
The equipment must be installed under standard conditions as outlined in section 5.3 and subsequently tested according to the specifications in sections 5.4.15.2 and 5.4.15.3, using only clean air During these tests, the equipment's indicators and alarms will be closely monitored.
During the testing the equipment shall not generate spurious inhibition, fault or alarm signals The equipment shall operate throughout the testing with degradation of performance allowed
No change of actual operating state or stored data is allowed
After the test, the equipment shall continue to operate as intended The measured value shall return to the original value within ±2 % of the measurement range
5.4.15.2 Short interruption of power supply
The power supply shall be interrupted for 10 ms, repeated ten times at random time intervals having a mean value of 10 s
For mains and DC powered equipment, the supply voltage should be increased by 10% and maintained until stabilized, followed by a reduction to 15% below the nominal voltage Each adjustment must occur within 10 milliseconds.
Recovery from power supply interruption
The equipment must be calibrated according to section 5.4.1 and then used with a gas cell that has a concentration of 25% of the test gas's measuring range After switching off the power for 30 minutes, the gas cell should be replaced with an equivalent optical cell containing a concentration of 50% of the measuring range Once the power is restored and the system stabilizes, the measured integral concentration should be recorded.
The measured integral concentration after restoration of the power shall be within ±20 % of the nominal value Alternatively, the equipment shall indicate a latched inhibit condition
NOTE The test requirement ensures proper start-up operation when gas is present.
Electromagnetic compatibility (EMC)
The equipment shall be subjected to a test method used in conducting EMC radiated immunity tests according to IEC 61000-4-1 and IEC 61000-4-3 The test shall be carried out in clean air
The test requirements shall be carried out with severity level 2; test field strength 3 V/m
NOTE 1 More severe electromagnetic immunity test parameters may be required for specific applications or for local regulations
Adjustable alarm equipment shall be set so that the lowest alarm level is 20 % of the calibrated measuring range
For general purpose rack-mounted control units, testing must be conducted within a manufacturer-supplied enclosure The instruction manual should clearly advise users to utilize the same enclosure to prevent negative electromagnetic interference.
The equipment must function correctly during tests without producing false inhibition, fault, or alarm signals Additionally, the integral concentration measurements for each gas should not deviate from the nominal values by more than ±10% of the measuring range or ±20% of the measured value, whichever is greater.
NOTE 2 For this test the operating distance may be relaxed to suit the requirements of the EMC test facility
NOTE 3 Electromagnetic emission requirements may be required by other standards.
Beam block fault
Adjustable alarm equipment shall be set to the lowest alarm level or 10 % of the full-scale gas concentration, whichever is greater
The opaque shutter must be operated at a consistent speed of 10 cm/s ± 5 cm/s while moving across the measuring radiation, ensuring that the beam is fully blocked before being retracted at the same speed.
The shutter must be operated in four directions at 90° intervals within a plane that is perpendicular to the measuring radiation axis For systems with separate transmitters and receivers, the positions should be within 100 mm of both the transmitter and receiver In the case of systems with a transceiver and reflector, the positions should also be within 100 mm of the transceiver and reflector.
The equipment will function normally without triggering false alarm signals until a beam blockage or inhibition signal occurs Once the shutter is removed from the "beam blocked" or "inhibition" position, the equipment will resume operation without generating any spurious alarm signals.
To ensure accurate readings, introduce a mid-range standard gas cell while the equipment operates in ambient air and record the stabilized measurements After removing the mid-range standard gas, quickly insert an opaque shutter into the beam from any direction until a beam blockage inhibition signal is triggered.
In the beam blocked condition, the mid-range standard gas cell should be positioned in the beam path, followed by the quick removal of the shutter The output measured within 30 seconds after the shutter is removed must not vary from the initial concentration in the test cell by more than ±10%.
Partial obscuration
Adjustable alarm equipment shall be set to the lowest alarm level or 10 % of the full-scale gas concentration, whichever is greater
Readings shall be taken with clean air and standard test gas
To conduct the test with equipment operating in air, introduce an obscuration mask that covers 50% of the receiver aperture Perform measurements in four directions at 90° intervals in a plane perpendicular to the radiation axis, maintaining a distance of less than 100 mm, starting from the vertical position For each orthogonal orientation, introduce clean air and standard test gas.
The equipment must function reliably without producing false alarm signals In any orientation, it should either indicate a fault signal or ensure that the measured values deviate from the initial values by no more than ±10% of the measuring range or ±20% of the measured value, depending on which is greater.
Long range operation
The equipment must be used at the maximum operating distance as specified in the manufacturer's instructions, ensuring that the ambient air and gas cell are maintained with clean air in the optical path.
To achieve a minimum radiation attenuation of 90%, the mask for beam attenuation (5.2.4.2) must be placed into the beam, accounting for the gas cell's attenuation Subsequently, the gas cell should be filled with the standard test gas.
The instrument must function continuously without generating inhibition, fault signals, or false alarms when exposed to clean air While attenuation may lead to noisier readings, the change in the average measured integral gas concentration upon mask insertion should not exceed ±10% of the measuring range or ±20% of the measured value, whichever is greater.
Direct solar radiation (applicable for equipment intended for outdoor use)
The transmitter and receiver shall be prepared as in 5.4.1, mounted as indicated in 5.2.3 and positioned as defined in 5.3.2
Sunlight will be directed towards the equipment's inlet aperture using a flat or composite mirror arrangement An iris will be placed in the beam path to ensure that only radiation from the sun's disc is captured The intensity of the radiation will be measured at the receiver's inlet aperture.
800 W/m 2 ± 50 W/m 2 Higher values of radiation intensity may be agreed upon by the manufacturer and test laboratory
NOTE 1 An appropriate mask may be used to attenuate the radiation
NOTE 2 An inclination greater than 30° above the horizon is generally necessary to achieve a light intensity of
The intensity of radiation from the transmitter measured at the entrance of the receiver aperture shall be attenuated to the value experienced when operating over maximum range
A mid-range test cell or gas simulation filter, as outlined in section 5.2.4.6, must be positioned near the transceiver or receiver It should be adequately sized to prevent any obstruction of the reflected radiation beam.
The mirror must be positioned to reflect solar radiation at fixed angles of +10°, +3°, -3°, and -10° relative to the optical axis of the equipment, with an angular tolerance of ±1° in two perpendicular planes.
NOTE 3 Where it is possible to rotate a receiver or transceiver about its optical axis, an alternative arrangement is for the mirror to be located successively at only two positions providing radiation incident at 10° ± 1° and 3° ± 1° to the optical axis and for the receiver or transceiver to be rotated about the optical axis of the instrument through 0° ± 1°, 90° ± 1°, 180° ± 1° and 270° ± 1° in each of the cases
At each inclination, the equipment shall be allowed to stabilise before measurements of the mid-range concentration are recorded
During the test, the equipment must remain operational without triggering any fault or alarm signals The stabilized measured signal at each angle of inclination should not exceed ±10% of the measuring range or ±20% of the measured value, whichever is greater.
To ensure the effectiveness of field verification equipment designed for periodic performance checks, it must undergo a specific testing procedure This includes calibrating the equipment as outlined in section 5.4.1 under the test conditions specified in section 5.3, and utilizing the field verification equipment according to the manufacturer's instructions.
The output signal obtained from the field verification equipment, when used according to the manufacturer's instructions, should not deviate from the expected response specified by the manufacturer by more than ±15% of the measuring range.
Labelling and marking
The equipment shall comply with the marking requirements of IEC 60079-0
NOTE Electrical equipment which does not fully comply with the relevant parts of IEC 60079-0 where equivalent safety is claimed, should be marked with the symbol “s”
In addition, the equipment shall also be marked: a) “IEC 60079-29-4” (to represent conformance with this performance standard); b) year of construction (may be encoded within the serial number).
Instruction manual
Each gas detection equipment, or each batch of equipment, shall be accompanied by instructions as required by 60079-0, including the following additional particulars:
The instruction manual must provide comprehensive and precise guidelines, including diagrams, for the safe operation, installation, and maintenance of the equipment It should detail essential safety precautions for handling, installation, operation, calibration, servicing, and storage, as well as disposal instructions for hazardous materials Additionally, it must outline the characteristics of interconnecting cables, installation procedures, initial start-up instructions, operating adjustments, and routine calibration checks, including the use of any provided verification equipment Finally, the manual should specify operational limitations where applicable.
The equipment is designed to operate effectively with specific gases and a defined range of integral concentrations, ensuring compliance with the relevant standards Additionally, for pre-set alarm systems, the specific concentration value at which the alarm is triggered is clearly stated.
2) the minimum integral path concentration that can be resolved;
3) maximum and minimum operational lengths of the open path;
4) ambient temperature limits, and details of any temperature corrections applied;
5) any influence of atmospheric composition including humidity;
6) ambient pressure limits, and details of any pressure corrections applied;
7) voltage range of the electrical supply, and frequency in the case of a.c supply;
8) effects and any operational constraints of extraneous optical sources (e.g sunlight, welding operations etc.);
9) unsuitable environmental conditions (e.g marine use);
10) response to very slow increases in path integral concentration;
When measuring integral path concentrations of gas during power supply interruptions, it is crucial to be aware of limitations The equipment's response characteristics for each intended gas or vapor must be clearly defined, along with the relative response to interfering substances Additionally, information regarding the adverse effects of environmental contaminants such as rain, snow, and dust is essential All indications and output signals should be significant, and methods for identifying malfunctions and corrective procedures must be detailed, including contact information for maintenance support It is important to specify whether alarm devices are latching or non-latching, provide a list of recommended replacement parts, and outline the storage life and conditions for the equipment and consumables Optional accessories and their effects on instrument characteristics should be listed, along with recommended cleaning procedures for optical components Special service conditions must be noted, and for battery-operated devices, instructions for installation, maintenance, disposal, and expected operating times should be included Finally, the time required for the equipment to operate within specifications after being powered on and any EMC limitations should be addressed.
Water vapour test apparatus include the following elements:
1 2 m pipe with quartz window material and gasket on each end Drain tube on each end and thermocouple port
2 Distilled water bottle and tubing
4 Heat tape with variac control
5 Stand or support for test fixture
Figure A.1 – Water vapour test apparatus
IEC 60050-426, International Electrotechnical Vocabulary (IEV) – Part 426: Equipment for explosive atmospheres
ISO 6142, Gas analysis – Preparation of calibration gas mixtures – Gravimetric method
ISO 6144, Gas analysis – Preparation of calibration gas mixtures – Static volumetric method
ISO 6145 (all parts), Gas analysis – Preparation of calibration gas mixtures using dynamic volumetric methods
4.1.1 Composants 43 4.1.2 Ensembles et composants électriques 43 4.1.3 Rayonnement optique 43 4.2 Construction 43
4.2.1 Généralités 43 4.2.2 Dispositifs d’indication 44 4.2.3 Alarme ou fonctions de sortie 44 4.2.4 Signaux de panne 44 4.2.5 Réglages 45 4.3 Matériel commandé par logiciel 45
4.3.1 Erreurs de conversion 45 4.3.2 Logiciel 45 4.3.3 Transmission de données 46 4.3.4 Auto-test individuel 46 4.3.5 Concept fonctionnel 46
5.2 Exigences générales pour les essais 47
5.2.1 Échantillons et séquence d'essais 47 5.2.2 Vérifications de la construction 48 5.2.3 Préparation des échantillons 48 5.2.4 Equipement pour étalonnage et essai 48 5.3 Conditions normales d’essai 51
5.3.1 Généralités 515.3.2 Distance fonctionnelle pour les essais de laboratoire 515.3.3 Gaz d’essai 515.3.4 Concentrations intégrales de gaz d’essai 525.3.5 Tension 525.3.6 Température ambiante 525.3.7 Humidité ambiante 525.3.8 Atmosphère ambiante 525.3.9 Préparation des matériels 535.3.10 Stabilisation 535.3.11 Options de communications 53
5.3.12 Matériel de détection de gaz constituant une partie de système 53 5.4 Méthodes d’essai 53
The initial preparation and procedure are crucial for ensuring optimal performance Non-powered storage must be managed effectively to maintain equipment integrity Calibration curves are essential, although they do not apply to fixed-setting alarm devices Stability and reliability of alarms are paramount, particularly in varying temperature conditions and in the presence of water vapor interference Equipment must withstand vibrations and pass drop tests for portable and transportable devices Proper alignment and response times are critical, alongside minimal operational times for intermittent reading devices Battery capacity and variations in external power supply must be monitored, as well as interruptions and transients in power Recovery after power interruptions is vital, and electromagnetic compatibility (EMC) must be ensured Equipment should also be resilient to beam blockage and partial obscuration, while maintaining functionality over long distances and under direct solar radiation for outdoor use.
6 Equipement de vérification sur site 64
Annexe A (informative) Matériel d’essai pour vapeur d’eau 66
Figure 1 – Matériel pour l’étalonnage de gaz et la vitesse de la réponse à l’essai 50
Figure A.1 – Matériel d’essai pour vapeur d’eau 66
Partie 29-4: Détecteurs de gaz – Exigences d’aptitude à la fonction des détecteurs de gaz inflammables à chemin ouvert
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La Norme internationale CEI 60079-29-4 a été établie par le comité d’études 31 de la CEI: Equipement pour atmosphères explosives
This standard complements and modifies the general requirements of IEC 60079-0 In cases where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of this standard takes precedence.
Le texte de cette norme est issu des documents suivants:
Le rapport de vote indiqué dans le tableau ci-dessus donne toute information sur le vote ayant abouti à l'approbation de cette norme
Cette publication a été rédigée selon les Directives ISO/CEI, Partie 2
Une liste de toutes les parties de la CEI 60079, sous le titre général Atmosphères explosives, est disponible sur le site web de la CEI
The committee has determined that the content of this publication will remain unchanged until the maintenance date specified on the IEC website at "http://webstore.iec.ch" in the data related to the publication in question On that date, the publication will be updated.
• remplacée par une édition révisée, ou
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Partie 29-4: Détecteurs de gaz – Exigences d’aptitude à la fonction des détecteurs de gaz inflammables à chemin ouvert
This section of IEC 60079-29 outlines the functional suitability requirements for equipment used to detect and measure flammable gases or vapors in ambient air The operation of this equipment is based on the measurement of spectral absorption by gases or vapors over extended optical paths, typically ranging from one meter to several kilometers.
Ce type de matériel mesure la concentration intégrale des gaz absorbants sur le chemin optique en unités telles que le LII mètre pour les gaz inflammables