1、BRITISH STANDARD BS1747-12: 1993 ISO10313: 1993 Methods for Measurement of air pollution Part12: Determination of the mass concentration of ozone in ambient air: chemiluminescence method UDC614.71:535.379.08:546.214BS1747-12:1993 This British Standard, having been prepared under the directionof the
2、Environment andPollution Standards Policy Committee, was published underthe authority of the Standards Board and comes intoeffect on 15October1993 BSI08-1999 The following BSI references relate to the work on this standard: Committee reference EPC/35 Draft for comment91/51946DC ISBN 0 580 22577 1 Co
3、mmittees responsible for this British Standard The preparation of this British Standard was entrusted by the Environment and Pollution Standards Policy Committee (EPC/-) to Technical Committee EPC/35, upon which the following bodies were represented: Association of Consulting Scientists BCIRA Britis
4、h Cement Corporation British Coal Corporation British Gas plc Combustion Engineering Association Department of Health Department of the Environment (Her Majestys Inspectorate of Pollution) Department of Trade and Industry (Laboratory of the Government Chemist) Department of Trade and Industry (Warre
5、n Spring Laboratory) Engineering Equipment and Materials Users Association GAMBICA (BEAMA Ltd.) Health and Safety Executive Institute of Petroleum Institution of Environmental Health Officers Institution of Gas Engineers National Society for Clean Air Royal Society of Chemistry The following bodies
6、were also represented in the drafting of the standard, through subcommittees and panels: Asbestosis Research Council British Steel plc Fibre Cement Manufacturers Association Ltd. Institute of Energy Lead Development Association Amendments issued since publication Amd. No. Date CommentsBS1747-12:1993
7、 BSI 08-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Definition 1 3 Principle 1 4 Reagents and materials 1 5 Apparatus 2 6 Procedure 4 7 Expression of results 5 8 Test report 6 Annex A (informative) Typical performance characteristics andspecificati
8、onsforthe chemiluminescence ozone analyser 7 Annex B (informative) Bibliography 7 Figure 1 Schematic diagram of a chemiluminescence ozone analyser 2 Figure 2 Schematic diagram of a typical ultraviolet photometriccalibrationsystem 3BS1747-12:1993 ii BSI 08-1999 National foreword This Part of BS1747,
9、which has been prepared under the direction of the Environment and Pollution Standards Policy Committee, is identical with ISO10313:1993 Ambient air Determination of the mass concentration of ozone Chemiluminescence method, published by the International Organization for Standardization (ISO) with t
10、he active participation and approval of the UK. This Part of BS1747 is one of a series relating to air quality arising from UK participation in the work of ISO/TC146. Methods for the determination of particular constituents of ambient air will be published as further Parts of this British Standard.
11、Topics relating to air quality characteristics will be published as Parts of BS6069 Characterization of air quality. Textual errors. When adopting the text of the International Standard, the textual errors given below were discovered. They have been marked in the text and have been reported to ISO i
12、n a proposal to amend the text of the internationalstandard. In4.4, note4, line1, “on” should be “of”. In7.1, in the list of symbols following the equation, “p” should be “P”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are re
13、sponsible 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 front cover, an inside front cover, pagesi andii, pages1 to7 and a back cover. This standard has been updated (see copyrig
14、ht date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS1747-12:1993 BSI 08-1999 1 1 Scope 1.1 General This International Standard specifies a chemiluminescence method for the determination of the mass concentration of ozone in amb
15、ient air. The method is applicable to the determination of the mass concentration of ozone between24g/m 3 0,001ppm(V/V) and10mg/m 3 5ppm(V/V) at the reference conditions of25 C and101,3kPa. Ultraviolet (UV) photometry is specified as the primary calibration method because of its proven accuracy and
16、specificity to ozone. The use of transfer standards is allowed if they have been previously calibrated against the primary calibration method. 1.2 Limitations The chemiluminescent reaction of ozone with ethylene is not subject to interference from any of the common air pollutants. However, particula
17、te matter, if not removed, will accumulate in the sampling line and may cause a measurable destruction of ozone. If particulate matter is allowed to enter the reaction chamber of the analyser, it will not only scatter the emitted light but will also accumulate on the optical window, thereby causing
18、further attenuation of the emitted light. Also, any nitrogen(II) oxide in the sampled air will to some extent react with the ambient ozone; therefore, the time during which the ambient air remains in the sampling line must be sufficiently short to keep this effect to a minimum. NOTE 1It has been rep
19、orted by some researchers that, at about80% relative humidity and22 C, the responses for some commercially available chemiluminescence analysers were about10% higher than that for dry air. However, comparisons of ambient ozone measurements using commercially available chemiluminescence and UV-photom
20、etric analysers showed no significant differences. This suggests that, in practice, any errors associated with calibrations using dry air are compensated by other effects. 2 Definition For the purposes of this International Standard, the following definition applies. 2.1 transfer standard an apparat
21、us (transportable) with associated operational procedures that is capable of accurately measuring or reproducing ozone concentration standards which are quantitatively related to the authoritative primary standard 3 Principle The air sample is drawn continuously, at a constant flow rate, through a p
22、article filter before it enters the chemiluminescence analyser. It then flows into a reaction chamber where it is mixed with an excess flow of ethylene. Ozone and ethylene react instantaneously to produce light in the visible region with a maximum at a wavelength of about400nm. The emitted light int
23、ensity is proportional to the concentration of ozone in the air sample and is measured by a photomultiplier tube. The resulting voltage is amplified, displayed, and calibrated in terms of the ambient ozone concentration. 4 Reagents and materials 4.1 Sampling line The sampling line shall be made of m
24、aterial that is inert to ozone, such as glass or fluorocarbon polymer, and it shall be as short as possible to keep the time the air sample remains them to a minimum. Any ambient nitrogen(II) oxide present in the air sample will react with some of the ozone during the time it remains in the sampling
25、 line. This decay of ozone is a complicated function of the mass concentration ratio, (O 3 )/ (NO), and the difference in mass concentrations, (O 3 ) (NO). Calculations have shown that, if the residence time is less than0,5s, the decay in initial ozone will be less than1% for most ambient ozone and
26、nitrogen(II) oxide concentrations encountered. Hence, it is recommended that the sampling line length and pumping speed be chosen such that the time the air remains within the sampling line is less than0,5s. However, in situations of routine monitoring, a time of up to5s is allowed. Any sampling lin
27、e or manifold preceding the filter shall be clean. Proper precautions shall be taken to prevent condensation inside the sampling line, for example, by heating the line. 4.2 Particle filter The filter and its support shall be made of material inert to ozone, such as fluorocarbon polymer, and it shall
28、 remove all particles likely to alter the performance of the analyser, it shall be changed on a regular basis, depending on the concentrations of ambient particles at the sampling site. This is necessary because excessive accumulation of particles on the filter can cause loss of ozone from the air s
29、ample and an excessive pressure drop across the filter. NOTE 2Frequently, a filter pore size of54m is used.BS1747-12:1993 2 BSI 08-1999 NOTE 3Generally, new filters need some time to be conditioned by the ambient atmosphere. As a result, measured mass concentrations of ozone have been observed to de
30、crease temporarily by5% to10% for periods of5min to15min immediately following filter changes. 4.3 Ethylene, of minimum purity99,5%. WARNING Ethylene has a lower explosive limit of27,5l/m 3 . Any excess shall be vented outdoors or, if necessary, chemically removed, especially at sites where hydrocar
31、bons are being measured. Observe standard safety precautions when using this flammable gas. 4.4 Zero air, required in the analyser calibration procedure. It shall be free of ozone, nitrogen oxides and any other interfering substance that can cause an undesired positive or negative response in either
32、 the ultraviolet photometer or the chemiluminescence analyser. The response of the ozone chemiluminescence analyser is affected by the oxygen content in the gas sample. Therefore, if synthetic air is used, the oxygen content shall be within 2% of the normal atmospheric concentration of20,9%. NOTE 4D
33、etails on a scrubbing system for making zero 1)air from ambient air may be found in1 and2 in Annex B. 5 Apparatus 5.1 Chemiluminescence analyser, consisting of sample and ethylene flow inlet systems, a constant temperature reaction chamber coupled to a photomultiplier detector and accompanying signa
34、l processing electronics. A flowmeter, if it is not an integral part of the analyser, shall be available for verifying that the flow meets the specifications of the instrument. A schematic diagram of a typical system is shown in Figure 1. 5.2 Apparatus for calibration, an ozone calibration system sh
35、all be used. (See the simplified schematic diagram in Figure 2.) NOTE 5An equivalent system would be one that uses only the air line with the ozone generator to bring zero and ozonized air to the manifold, hence eliminating the need for the four-ports two-way valve. 1) See national foreword for deta
36、ils of textual error. Figure 1 Schematic diagram of a chemiluminescence ozone analyserBS1747-12:1993 BSI 08-1999 3 5.2.1 Ultraviolet photometer, for primary calibration only consisting of a low pressure mercury discharge lamp, a single or dual absorption cell, and detection and signal processing ele
37、ctronics. It shall be meticulously maintained. To prevent ozone generation within the absorption cell, a high-silica glass window (or equivalent) shall be inserted between the mercury lamp and the absorption cell to remove the185nmHg line but transmit the253,7nmHg measurement line. The detector shal
38、l be capable of measuring the transmittance through the absorption cell at a wavelength of253,7nm, with less than0,5% of the radiation detected being from other wavelengths (vacuum photodiodes with a caesium telluride sensitization meet this requirement). The length of the light path through the abs
39、orption cell shall be known to an accuracy better than0,5%, and the cell and associated plumbing shall be designed to minimize surface loss of ozone. Provision shall be made for measuring the temperature and pressure of the gas in the absorption cell (see5.2.8 and5.2.9). See the simplified schematic
40、 diagram of a photometer system in Figure 2. 5.2.2 Ozone generator, which generates stable ozone concentrations that, in turn, are measured by the calibrated photometer(5.2.1). The ozone generator shall be capable of producing steady ozone concentrations in the range of measurement, at the required
41、flow rate, and throughout the period of calibration. If a variable ozone generator is not available, the calibration system shall include a means of suitably diluting the ozone with additional zero air (see4.4). In such a case, a mixing chamber shall be installed before the output manifold. WARNING
42、Ozone is a toxic gas with a threshold limit value in air of0,1ml/m 3 , and any excess should be vented into an activated charcoal scrubber or outdoors (well away from any sampling intake). 5.2.3 Airflow controllers, capable of maintaining steady airflows throughout the period of calibration. 5.2.4 A
43、irflow meters, of any type that is suitable for measuring the required airflows. NOTE 6The actual airflows are not used in the calculations but are used only for achieving the nominal concentrations required in the calibration procedure. Figure 2 Schematic diagram of a typical ultraviolet photometri
44、c calibration systemBS1747-12:1993 4 BSI 08-1999 5.2.5 Air pump, used to draw the required sample flow through the absorption cell. 5.2.6 Output manifold, made of materials inert to ozone, such as glass or fluorocarbon polymer. It shall be of sufficient diameter and be vented to ensure equal atmosph
45、eric pressure inside and outside the manifold. The vent shall be located so as to prevent intrusion of ambient air. 5.2.7 Four-ports two-way valve, with interior surfaces made of a material inert to ozone, such as a fluorocarbon polymer. When a calibration system such as that shown in Figure 2 is us
46、ed, a four-ports two-way valve or some equivalent system of valves shall be used for switching the manifold flow between zero air and the ozone test atmosphere. 5.2.8 Temperature indicator, capable of measuring temperature with an accuracy of0,1 C. 5.2.9 Pressure indicator, capable of pressure with
47、an accuracy of 0,1kPa. 6 Procedure 6.1 Operation of chemiluminescence analyser Install the instrument in a suitable location. Follow the manufacturers operating instructions for the specific analyser in use to set the various parameters, including sample and ethylene flow rates. Check to ensure that
48、 the manufacturers performance characteristics are met or exceeded. If necessary, the location shall also be temperature controlled, so as to minimize the effect of the temperature dependence of the instrument. (SeeAnnex A for typical performance specifications.) Introduce the air sample into the in
49、strument and record the ozone concentration by means of a suitable recording device (for example, chart recorder, electronic data acquisition system,etc.). NOTE 7During continuous operation of the instrument, it is recommended that a multipoint calibration be carried out every3months. In addition, frequent operational checks on the instrument zero and span should be made, usually once a week. 6.2 Calibration of the chemiluminescence analyser 6.2.1 Principle A schematic diagram of an ultraviolet photometric calibration system is shown in F
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