1、BS ISO15337:2009ICS 13.040.20NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDAmbient air Gasphase titration Calibration ofanalysers for ozoneThis British Standardwas published under theauthority of the StandardsPolicy and StrategyCommittee on 31 May 2009 BSI 200
2、9ISBN 978 0 580 58658 3Amendments/corrigenda issued since publicationDate CommentsBS ISO 15337:2009National forewordThis British Standard is the UK implementation of ISO 15337:2009.The UK participation in its preparation was entrusted to TechnicalCommittee EH/2/3, Ambient atmospheres.A list of organ
3、izations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.
4、BS ISO 15337:2009Reference numberISO 15337:2009(E)ISO 2009INTERNATIONAL STANDARD ISO15337First edition2009-04-15Ambient air Gas phase titration Calibration of analysers for ozone Air ambiant Titrage en phase gazeuse talonnage des analyseurs dozone BS ISO 15337:2009ISO 15337:2009(E) PDF disclaimer Th
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9、y in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2009 All rights reservedBS ISO 15337:2009ISO 15337:2009(E) ISO 2009 All rights reserved iiiFo
10、reword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a tec
11、hnical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters o
12、f electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated
13、to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible fo
14、r identifying any or all such patent rights. ISO 15337 was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 3, Ambient atmospheres. BS ISO 15337:2009ISO 15337:2009(E) iv ISO 2009 All rights reservedIntroduction For ambient ozone (O3) analysers, the primary standard measuremen
15、t principle for calibration is UV photometry. This International Standard provides an alternative secondary measurement principle and method based on gas phase titration of an O3gas mixture with excess nitric oxide (NO). When using this method, the generated O3calibration gases are traceable to a ce
16、rtified primary NO measurement standard. BS ISO 15337:2009INTERNATIONAL STANDARD ISO 15337:2009(E) ISO 2009 All rights reserved 1Ambient air Gas phase titration Calibration of analysers for ozone 1 Scope This International Standard specifies the gas phase titration (GPT) method for the calibration o
17、f ambient air ozone (O3) analysers. The method is applicable to the calibration of O3concentrations in the range 10 g m3(5 nmol mol1mole fraction) to 2 000 g m3(1 000 nmol mol1mole fraction). This International Standard uses the reference conditions of 25 C and 101,325 kPa; however, reference temper
18、atures of 0 C and 20 C are also acceptable. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any ame
19、ndments) applies. ISO 7996, Ambient air Determination of the mass concentration of nitrogen oxides Chemiluminescence method 3 Principle Gas phase titration (GPT) is based on the simple gas phase bimolecular reaction: 322NO O NO O+U (1) with a bimolecular reaction rate constant of 1,8 1014cm3molecule
20、1s1(or 0,44 mol mol1s1when concentrations are expressed as mole fractions) at 298 K. This reaction is fast, and equilibrium lies far to the right hand side of Expression (1) if the kinetic conditions specified in Annex A are satisfied. This International Standard is based on mixing O3with excess nit
21、ric oxide (NO) in a dynamic flow system where, first, the NO and O3are mixed at relatively high concentrations (to effect essentially complete reaction of the O3) and, second, the reaction products and any excess NO are then diluted with zero reference gas (e.g. synthetic air) to final calibration c
22、oncentrations. Since the reaction is stoichiometric, the molar decrease in measured NO is equal to the added O3; this is also equal to the nitrogen dioxide (NO2) reaction product. The NO is obtained from a certified NO measurement standard, a calibrated gas mixture in a compressed gas cylinder. Othe
23、r calibrated sources could be used (e.g. see VDI 2453-3 11), and adapted to the GPT calibration apparatus. The change in NO concentration at the GPT output manifold is measured by a chemiluminescence NO analyser. A stable O3generator is used to produce variable concentrations of the gas to cover the
24、 calibration range of interest. BS ISO 15337:2009ISO 15337:2009(E) 2 ISO 2009 All rights reserved4 Reagents and materials 4.1 Sample line and connectors, made of material that is inert to O3and NO, such as glass or fluorocarbon polymer e.g. perfluoro(alkoxy alkane) (PFA), polytetrafluoroethylene (PT
25、FE) or perfluoro (ethylene-propylene) plastic (FEP) are acceptable; these shall be as short as possible to keep the residence time to a minimum. NOTE Whenever a sampling line is cleaned or replaced, it can take several hours to equilibrate with ambient conditions. 4.2 Zero reference gas, for calibra
26、tion of the GPT procedure. If synthetic air is used, the oxygen (O2) content shall be at the normal atmospheric concentration of 20,9 % 2 % volume fraction. No O3, nitrogen oxides or any other interfering substance that can cause an undesired measurable positive or negative response in the analysis
27、shall be detectable in the zero air. NOTE Details on a system for making zero air from ambient air can be found in ASTM D5011 9. 4.3 NO measurement standard, stored in a compressed gas cylinder and containing a known concentration of NO in nitrogen, in the range 10 mol mol1to 100 mol mol1, for use i
28、n the calibration procedure. This NO cylinder shall be traceable to a primary measurement standard (e.g. a certified reference material), and the NO2impurity shall be less than 0,5 % mass fraction of the NO concentration. 5 Apparatus Usual laboratory equipment and, in particular, the following. 5.1
29、Ozone generator, capable of producing steady O3concentrations in the required range throughout the period of the calibration. Conventional UV low-pressure mercury vapour lamps are adequate for this purpose; however, both voltage and temperature regulation shall be provided for a stable O3output. CAU
30、TION Ozone is a toxic gas and good laboratory practice should limit indoor ozone concentrations to less than 200 g m3(100 nmol mol1). Consult a reference text for more details on hazards of ozone and appropriate safety precautions. Any excess should be vented into an activated charcoal scrubber (wit
31、h negligible back-pressure) or outdoors well away from any sampling intake. Comply with any local regulations currently in force for handling, use and disposal of ozone. 5.2 Gas flow controllers and meters: there are two options for controlling and measuring the gas flows; see 5.2.1 and 5.2.2. Elect
32、ronic mass flow controllers (5.2.1) are recommended because of their inherent low measurement uncertainty and greater precision. 5.2.1 Electronic mass flow controllers, calibrated and capable of maintaining constant gas flow rates within 0,5 % throughout the calibration period. Components in contact
33、 with NO shall be of a non-reactive material. 5.2.2 Manual gas flow control and meters, capable of maintaining constant gas flow rates within 2 % throughout the calibration period. The gas flow meters shall be capable of measuring the required gas flows within 2 %. 5.3 Reaction chamber, to provide a
34、 suitable environment for the quantitative reaction between NO and O3at high concentration. This chamber shall be made of materials inert to O3and nitrogen oxides, such as borosilicate glass, PFA, FEP or PTFE. Its volume shall be limited so that the residence time of the gas mixture in this volume i
35、s less than 60 s (see Annex A for predetermining the volume for given flow conditions). 5.4 Dilution chamber, to provide a suitable environment for the mixing of reaction products and dilution air. It shall be made of materials inert to O3and nitrogen oxides, such as borosilicate glass, PFA, FEP or
36、PTFE. Its volume should be sufficiently large to allow complete mixing of the gas components, but small enough to limit the residence time to less than 60 s. BS ISO 15337:2009ISO 15337:2009(E) ISO 2009 All rights reserved 35.5 Output manifold, to serve as a multi-port interface to allow sampling of
37、the output from the GPT calibration system. It shall be made of materials inert to O3, such as borosilicate glass, PFA, FEP or PTFE. It shall be of sufficient diameter and be vented to ensure an insignificant pressure drop from inside to outside the manifold. The vent outlet shall be located downstr
38、eam of the other outlet ports so as to prevent intrusion of ambient air. 5.6 Temperature sensor, to measure the temperature of the detection cell of the O3analyser, readable to within 0,5 C. 5.7 Pressure meter, to indicate the pressure in the detection cell of the O3analyser, readable to within 2 hP
39、a. 5.8 Chemiluminescence nitrogen oxides analyser, whose NO channel meets the requirements of ISO 7996. The purpose of this instrument is to determine quantitatively the decrease in NO response equivalent to the O3added in the GPT system. NOTE Additional details on calibrating such an analyser can b
40、e found in VDI 2453-2 10. 5.9 Pressure regulator for source gas cylinder, whose internal components are inert to NO. 6 Calibration procedure 6.1 Overview A schematic diagram of a calibration system is shown in Figure 1. The following procedure is written for the option where a) both NO and O3analyse
41、rs are simultaneously sampling the output manifold of the GPT system, b) concentrations are expressed as mole fractions, in nanomoles per mole. A suitable and accurately known NO concentration in air is generated and measured with the chemiluminescence NO analyser (5.8). Then, O3is generated to titr
42、ate some of the NO. The decrease in NO is equal to the added O3. Finally, with the O3generator (5.1) still on, the NO flow is turned off so that the ambient O3analyser can measure the known O3concentration via the common manifold. By varying the O3generator output, other known O3concentrations can b
43、e generated in a similar manner. A linear least squares analysis of the O3analyser responses and corresponding calculated O3concentrations will produce a linear calibration function for the O3analyser. The linearity of the chemiluminescence NO analyser shall have been recently verified by means of a
44、 linear least squares analysis on its calibration data, and the calculated correlation coefficient shall be better than 0,99 for the NO calibration range of interest. (It should be noted that the calibration function for the NO analyser need not be used in the following calibration calculations.) 6.
45、2 Calibration of the ambient ozone analyser 6.2.1 Install the instruments in a suitable location and provide temperature control of the measurement room to minimize any temperature dependence of the instruments. Follow the manufacturers operating instructions for the analysers to set the various ope
46、rating parameters correctly, including the sample flow rate and, if applicable, activation of the electronic temperature and pressure compensation on the O3analyser. Also, follow the diagnostic procedure as outlined in the manufacturers operations manual to verify that instrument functions are withi
47、n their performance specifications. The measured concentrations should be recorded by means of a suitable recording device (e.g. chart recorder or electronic data acquisition system). BS ISO 15337:2009ISO 15337:2009(E) 4 ISO 2009 All rights reservedFigure 1 Schematic diagram of a typical ozone calib
48、ration flow system for use with GPT In the calculations to follow, concentrations are expressed as mole fractions. The calibration shall include measurements using zero air (see 4.2) and at least five O3concentrations, which should be reasonably spaced to cover the entire calibration range. For all
49、calibrations, the input flow rate to the manifold shall exceed the total flow rate required by the instruments attached to the manifold by at least 10 %, with the excess appropriately vented at atmospheric pressure. Carry out steps 6.2.2 to 6.2.11 in the calibration procedure. 6.2.2 Establish the GPT system parameters as set out in Annex A and assemble the apparatus as shown in Figure 1; ensure that the entire calibration flow system is free of leaks. 6.2.3 Introduce zero air (4.2) i
