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1、BRITISH STANDARD BS ISO 13964:1998 Air quality Determination of ozone in ambient air Ultraviolet photometric method ICS 13.040.20 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:19:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 13964:1998 This British Standard, having been prepared u
2、nder the direction of the Health and Environment Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 November 1998 BSI 05-1999 ISBN 0 580 30733 6 National foreword This British Standard reproduces verbatim ISO 13964:1998 and implements it as the
3、 UK national standard. The UK participation in its preparation was entrusted by Technical Committee EH/2, Air quality, to Subcommittee EH/2/3, Ambient atmospheres, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any e
4、nquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this subcommittee can be obtained on request to its secretary. Cross-references T
5、he British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A
6、 British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a
7、 front cover, an inside front cover, pages i and ii the ISO title page, pages ii to iv, pages 1 to 10 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments is
8、sued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:19:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 13964:1998 BSI 05-1999i Contents Page National forewordInside front cover Forewordiii Text of ISO 139641 Licensed Copy: sheffieldun sheffieldu
9、n, na, Sun Nov 26 03:19:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:19:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:19:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO
10、13964:1998 ii BSI 05-1999 Contents Page Forewordiii 1Scope1 2Interferences1 3Principle1 4Reagents and materials2 5Apparatus3 6Procedure6 7Expression of results7 8Test report8 Annex A (informative) Some reported chemical interferents for UV photometric ozone analysers9 Annex B (informative) Correctio
11、n for ambient nitric oxide9 Annex C (informative) Typical performance specifications for a UV photometric ozone analyser9 Bibliography10 Figure 1 Schematic diagram of a typical UV photometer system4 Figure 2 Schematic diagram of a typical ozone calibration flow system for use with UV photometry5 Des
12、criptors: Air, quality, air pollution, chemical analysis, determination of content, ozone. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:19:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 13964:1998 BSI 05-1999iii Foreword ISO (the International Organization for Standardization) is
13、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 technical committee has been established has the right to be represent
14、ed 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 of electrotechnical standardization. International Standards are dra
15、fted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote
16、. International Standard ISO 13964 was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 3, Ambient atmospheres. Annex A, Annex B and Annex C of this International Standard are for information only. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:19:03 GMT+00:00 2006
17、, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:19:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 13964:1998 BSI 05-19991 WARNING This document calls for use of ozone gas. Ozone is a toxic gas and good laboratory practice should limit indoor ozon
18、e concentrations to less than 200 4g/m3 (volume fraction 1 107). Consult a reference text for more details on hazards and safety of ozone. Any excess should be vented into an activated charcoal scrubber (with negligible back-pressure) or outdoors well away from any sampling intake. 1 Scope This Inte
19、rnational Standard specifies an ultraviolet (UV) photometric method for the determination of ozone in ambient air. It is applicable to the determination of ozone concentrations in the range 2 4g/m3 (volume fraction of 1 109) to 2 mg/m3 (volume fraction of 1 106). Furthermore, this International Stan
20、dard uses the reference conditions of 25 C and 101,25 kPa; however, reference temperatures of 0 C and 20 C are also acceptable. For calibration, this International Standard specifies ultraviolet photometry as the primary reference procedure because of its proven accuracy and specificity to ozone. Th
21、e use of secondary reference procedures (often called transfer standards), including non-UV methods, is allowed if they have been previously calibrated by the primary UV reference procedure (see ISO 6879 for definitions). 2 Interferences The UV photometric method is not subject to interference from
22、any of the common gaseous air pollutants at ambient concentrations less than 0,2 mg/m3 (volume fraction of 1 107). However, there are reported interferences of about 2 4g/m3 (volume fraction of 1 109) and about 8 4g/m3 (volume fraction of 4 109) in equivalent ozone for nitrogen dioxide and sulfur di
23、oxide concentrations at a volume fraction of 0,5 106, respectively. Additionally, there are some reported interferents for instruments using a manganese dioxide ozone scrubber; these are tabulated in Annex A of this International Standard. Particulate matter, if not removed, will accumulate in the s
24、ampling line and may cause a measurable destruction of ozone. Ambient nitric oxide in the sample air will to some extent react with the ambient ozone during the residence time of the ambient air in the sampling line; corrections for this effect are given in Annex B of this International Standard. Fo
25、r ozone analysers with single absorption cells, any ambient pollutant that absorbs the photometers UV radiation and that varies in concentration within the cycle time of the instrument may cause an interference. A similar limitation applies at a site where the ambient ozone concentration itself vari
26、es on this time scale, as for example, at traffic intersections. NOTEIn general, if interferences are suspected, it is preferable to use another method (for example, the chemiluminescence method using ethylene, see 2) rather than attempting to scrub out the interfering agent, because the instability
27、 of ozone makes the testing and proving of scrubbers particularly difficult. 3 Principle Sample air is drawn continuously through an optical absorption cell where it is irradiated lengthwise by monochromatic radiation, centred on 253,7 nm, from a stablilized low-pressure mercury (Hg) discharge lamp.
28、 The UV radiation which passes through the absorption cell is measured by a sensitive photodiode or photomultiplier detector and converted to a measurable electrical signal. Absorption of this radiation by the sample air within the absorption cell is a measure of the ambient ozone concentration. An
29、ozone catalytic converter is used to selectively remove the ozone from the sample stream. This can be done either for the sample absorption cell (single-cell configuration) or a separate but identical reference absorption cell (dual-cell configuration); either configuration is acceptable. Licensed C
30、opy: sheffieldun sheffieldun, na, Sun Nov 26 03:19:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 13964:1998 2 BSI 05-1999 The Beer-Lambert law on light absorption is used to relate the measured UV transmittance to the path length of the absorption cell, the ozone absorption coefficient at 253
31、,7 nm and the ozone concentration. The following equation gives this relationship: where Most modern commercial ozone analysers measure the temperature and pressure of the sample air in the absorption cell. Using this data, an internal microprocessor automatically calculates the measured ozone conce
32、ntration relative to some chosen reference condition. For analysers without this automated pressure and temperature compensation, the concentrations need to be corrected manually to the chosen reference condition (TrefC and 101,25 kPa) according to the following equation: where 4 Reagents and materi
33、als 4.1 Sample line, made of material that is inert to ozone, such as glass or fluorocarbon polymer, and shall be as short as possible to keep the residence time to a minimum. Any ambient nitric oxide present in the sample air will react with some of the ozone during the residence time in the sampli
34、ng line. This decay of ozone is a function of the ambient ozone and nitric oxide concentrations (see note below). Calculations have shown that if the residence time is less than 0,5 s, then the decay in initial ozone will be less than 1 % for most ambient ozone and nitric oxide concentrations encoun
35、tered. Hence, it is recommended that the sampling line length and flowrate be chosen such that the residence time within the sampling line be as short as possible; a residence time of up to 5 s is allowed. It is recommended that a particle filter (see 4.2) be installed at the sampling inlet to keep
36、the whole inlet system clean. In case there is a sample line or manifold preceding the inlet particle filter (see 4.2), it shall be clean. Proper precautions shall be taken to prevent condensation inside the sample line, for example, by appropriate heating of the line. NOTE 1Annex B describes the co
37、rrection for the reaction of ambient ozone with nitric oxide in the sampling line. NOTE 2Whenever a sampling line is cleaned or replaced, it may take several hours to equilibrate with ambient conditions. 4.2 Particle filter and its support, made of material inert to ozone, such as polytetrafluoroeth
38、ylene (PTFE), and capable of removing all particles likely to alter the performance of the analyser. It shall be changed on a regular basis, depending on the ambient particle concentrations at the sampling site; however, the period between filter changes should not exceed 14 days. This is necessary
39、because excessive accumulation of particles on the filter can cause loss of ozone from the sample air. Transmittance = I/Io = exp( aCd)(1) I/Iois the transmittance of the ozone sample, i.e. the ratio of the irradiance (commonly called light intensity) falling on the detector when the absorption cell
40、 contains sample air to the irradiance when the cell contains ozone-scrubbed air; ais the ozone absorption coefficient at 253,7 nm, in square metres per microgram; (a = 1,44 105m2/4g; see 3); Cis the mass concentration of ozone, at the sample temperature and pressure in the absorption cell, in micro
41、grams per cubic metre; dis the optical path length, in metres. (2) Crefis the mass concentration of ozone, at the reference temperature (Tref) and pressure (101,25 kPa), in micrograms per cubic metre; Tis the sample temperature of the absorption cell, in degrees Celsius; Pis the sample pressure in t
42、he absorption cell, in kilopascals; Trefis the reference temperature, in degrees Celsius; Cis the mass concentration of ozone from equation (1), at the sample temperature (T) and pressure (P) in the absorption cell, in micrograms per cubic metre. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 2
43、6 03:19:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 13964:1998 BSI 05-19993 NOTEFrequently, a filter pore size of 5 4m is used. NOTEGenerally, new filters need some time to be conditioned by the ambient atmosphere. As a result, measured ozone concentrations have been observed to decrease te
44、mporarily by 5 % to 10 % for periods of 5 min to 15 min immediately following filter changes. 4.3 Zero air, required in the analyser calibration procedure. If synthetic air is used, the oxygen content shall be at the normal atmospheric concentration of (20,9 2) %. The zero air shall be free of ozone
45、, nitrogen oxides and any other interfering substance that can cause an undesired measurable positive or negative response in the UV photometer. Different zero air supplies may have different remnant impurities and, in turn, these can cause different UV transmittances of the air samples. Hence, the
46、zero air supplied to the photometer during the Io measurement see equation (1) shall be the same as that used for generation of the calibration ozone concentrations. NOTEDetails on a system for making zero air from ambient air may be found in 4. 5 Apparatus 5.1 UV photometric ambient ozone analyser
47、The components of a typical UV photometric ozone measuring system with a single-cell configuration are shown schematically in Figure 1. When assembled, they become part of a UV photometric ambient ozone analyser with specifications conforming to those listed in Annex C. Commercial instruments that m
48、eet these specifications are readily available in either single or dual cell configurations. The important components of such a system are as follows. a) Ultraviolet absorption cell, constructed of material inert to ozone, such as fluorocarbon polymer, borosilicate glass, fused silica or fluorocarbo
49、n-coated metal. It shall be mechanically stable so that any optical alignments are not affected by vibration or change in ambient temperature. Provision shall be made for measuring the temperature and pressure of the gas in the absorption cell see 5.1 h) and 5.1 i). b) Ultraviolet source lamp, i.e. a low-pressure mercury vapour discharge lamp that emits monochromatic UV radiation centred at 253,7 nm. The UV radiance of this lamp shall be electronically stabilized so that the analyser meets the required performance specific
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