1、BRITISH STANDARD BS 1747-11: 1993 ISO 9835:1993 Methods for Measurement of air pollution Part 11: Determination of a black smoke index in ambient air UDC 614.715:543.275.3:531.082.531BS1747-11:1993 This British Standard, having been prepared under the directionof the Environment andPollution Standar
2、ds Policy Committee, was published underthe authority of the Standards Board and comes intoeffect on 15 September 1993 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference EPC 35 Draft for comment 91 51945 DC ISBN 0 580 22506 2 Committees responsible for
3、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 British Cement Association Brit
4、ish Coal Corporation British Gas plc Combustion Engineering Association Department of the Environment (Her Majestys Inspectorate of Pollution) Department of Health Department of Trade and Industry (Laboratory of the Government Chemist) Department of Trade and Industry (Warren Spring Laboratory) Engi
5、neering Equipment and Materials Users Association European Resin Manufacturers 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 Amend
6、ments issued since publication Amd. No. Date CommentsBS1747-11:1993 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Definition 1 3 Principle and theory 1 4 Apparatus 1 5 Procedure 2 6 Expression of results 2 7 Test report 4 Annex A (informative)
7、 Conversion of absorption coefficient to traditional black smoke units 5 Figure 1 Alternative sampling arrangements for black smoke measurement 3 Figure 2 Reflectometer response 4 Figure A.1 Black smoke calibration curve 7 Table 1 Confidence limits for absorption coefficients 4 Table A.1 Absorption
8、coefficient and black smoke index 8BS1747-11:1993 ii BSI 07-1999 National foreword This Part of BS 1747 has been prepared under the direction of the Environment and Pollution Standards Policy Committee. It is identical with ISO 9835:1993 Ambient air Determination of black smoke index, published by t
9、he International Organization for Standardization (ISO) with the active participation and approval of the UK. This Part of BS 1747 is one of a series relating to air quality arising from UK participation in the work of ISO/TC 146. Methods for the determination of particular constituents of ambient a
10、ir will be published as further Parts of this British Standard. Topics relating to air quality characteristics will be published as Parts of BS 6069 Characterization of air quality. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards
11、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 front cover, an inside front cover, pages i and ii, pages1 to 8 and a back cover. This standard has been updated (se
12、e copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.ISO9835:1993(E) BSI 07-1999 1 1 Scope This International Standard specifies a method for measuring the black smoke index of an ambient air sample. The method is based o
13、n the staining effect of particles which is produced when a sample of air is drawn through a filter paper. The method is intended for the measurement of a black smoke index in the range 6 to 375 in the ambient atmosphere. It is based on the measurement of reflectance. The method does not measure the
14、 mass concentration of particles directly. 2 Definition For the purposes of this International Standard, the following definition applies. 2.1 black smoke strongly light-absorbing, particulate material suspended in the ambient atmosphere NOTE 1The major contributor to black smoke is soot particles;
15、i.e.particles containing carbon in its elemental form. 3 Principle and theory Air is drawn through a filter paper and the reflectance of the stain produced is measured. If it is assumed that reflected light from the surface of the filter paper has passed through the layer of light absorbent particle
16、s twice, reflectance from the filter surface is analogous to the absorption of light by particles suspended in air in accordance with the equation where Thus, rearranging equation (1): The method specified in this International Standard can be used to measure the absorption coefficient on any filter
17、 material, but the conversion of absorption coefficient or extinction coefficient to what is, by convention, known as the black smoke index, is purely an arbitrary operation which is carried out by reference to tables or graphs. For further explanations, seeAnnex A. 4 Apparatus 4.1 Sampling equipmen
18、t. The sampler shall be designed for daily operation, or it shall be of an automatic type for continuous operation. Flow diagrams of alternative arrangements of sampling equipment are shown inFigure 1. Details of the sampling equipment are given in4.1.1 to 4.1.6. 4.1.1 Air intake, a conical funnel o
19、f 30mm to50mm diameter that is constructed of polyvinylchloride. The funnel shall be mounted vertically with the mouth downwards at a height of not less than 2,5m and not greater than 5m above the ground. The inlet shall be located at least 1m horizontally from any external walls. 4.1.2 Connection t
20、ubing, constructed of polyvinylchloride, of internal diameter 8mm 1mm and not greater than 6m inlength. Bends shall be avoided if possible but, ifunavoidable, shall have a radius greater than50mm. 4.1.3 Filter unit. The filter holder shall be constructed of an electrically conducting and chemically
21、inert material (with respect to the atmosphere likely to be encountered). The area of the aperture shall be 5cm 2+ 5%. The leakage across the filter and valves (if used) shall not exceed2% of the total flow rate. The filter holder should be of a design which will provide a homogeneous particle layer
22、 on the surface of the filter medium. The homogeneity of the particle layer can be checked by measuring the reflectance at several points across the diameter of the stain produced by sampling particles using the filter holder. The variation in reflectance across the stain shall not exceed 1percentag
23、e unit of reflectance. 4.1.4 Filter material. The filter membrane shall have a collection efficiency of as close to 100% as possible in the 0,1micron to 5micron particle size range. Variations in reflectance across the whole surface area shall not exceed 1reflectance unit. In addition, the filter ma
24、terial shall be suitable for a flow rate of 2m 3 /d. NOTE 2The reflectance of unused filters may vary from batch to batch, and it is therefore necessary to check and adjust for the variability of the filters before use. . . . (1) R is the intensity of reflected light from the surface of a stained pa
25、per; R 0 is the intensity of reflected light from the surface of a clean paper; A is the area of the stain on the filter paper, in square metres; V is the volume sampled, in cubic metres; a is the absorption coefficient, in reciprocal metres. . . . (2) RR 0exp2aV A - = a A 2V -In R 0 R - =ISO 9835:1
26、993(E) 2 BSI 07-1999 4.1.5 Sampling pump, capable of delivering up to2,0l/min of air with the filter in line. If a membrane pump is used, a 0,2litre ballast shall be incorporated to minimize pressure fluctuations. The pump is placed before the flow or volume meter (seeFigure 1). 4.1.6 Volume measure
27、ment and flow rate control, consisting of a sampler equipped with a flow controller capable of keeping the flow rate constant to within 5% of the measured flow. Measure the volume sampled by either a) recording the elapsed time and calculating the volume sampled under the control of the flow control
28、ler; or b) reading the volume directly from a dry gasmeter having an accuracy of at least 5% of the measured volume (the sampling flow rate shall be2m 3 /d 0,2m 3 /d). 4.2 Reflectometer, consisting of a light source and detector and having either an analogue or digital readout of either the percenta
29、ge reflectance (linear scale; 0 to100% reflectance) or the extinction coefficient (logarithmic scale; 0 toinfinity) type. The points on the density chart 1)shall be within the limits shown inFigure 2. Instruments designed according to the requirements mentioned in this subclause shall be capable of
30、measuring the absorption coefficient with a precision of better than 5% at absorption coefficients greater than 1 10 5 m 1 . 5 Procedure 5.1 Sampling Assemble the sampling train in the order illustrated inFigure 1 using the specified connection tubing(4.1.2) for all connections. Place a clean sheet
31、of filter paper(4.1.4) in the filter unit. If the two faces of the paper do not have the same texture, place the paper so that the suspended particulate matter is collected on the smoother surface. Assemble the filter unit(4.1.3) according to the manufacturers instructions. Check the assembled equip
32、ment for leakage. Record the initial reading of the gasmeter (if fitted). Start the sampling pump(4.1.5), adjust the sampling rate to 1,4l/min(2m 3 /d) and note the starting time. Sample for 24h. At the end of the sampling period, record the flow rate and time, switch off the sampling pump and recor
33、d the final reading of the dry gasmeter (iffitted) and the sampling period to the nearest hour and minute. Calculate the volume sampled, incubic metres, using the flow rate and the sample duration or using the readings of the dry gasmeter. (See also4.1.6.) 5.2 Calibration of the reflectometer Calibr
34、ate the reflectometer according to the manufacturers instructions. 5.3 Measurement of the reflectance of smoke stains 5.3.1 Calibrate the reflectometer at least once per month using the procedure described in5.2. 5.3.2 Set the reflectometer to 100% reflectance (zero absorbance) on a clean filter pap
35、er according to the reflectometer manufacturers instructions. 5.3.3 Replace the clean filter paper by an exposed one (see5.1), measure the reflectance according to the manufacturers instructions and record the reflectometer reading (which will be less than 100% reflectance or more than zero absorban
36、ce). The measured reflectances shall lie in the range35% to 95% reflectance, corresponding to a range of 0,64 to 13,13 10 5for the absorption coefficient. 5.3.4 Check the 100% adjustment of the reflectometer on a clean filter paper at frequent intervals, for example at least after every10smokestains
37、, and readjust if necessary. 6 Expression of results 6.1 Calculation Calculate the absorption coefficient a, in reciprocal metres, using equation (2) where Report the absorption coefficient to the first decimal place. NOTE 3Table A.1 may be used to convert the absorption coefficient, a, to the black
38、 smoke index, in line with the OECD or EEC reference methods. 1) Kodak Publication No. Q-16. . . . (3) R is the reflectance of the stained paper, in percentage of R 0 ; R 0 is the reflectance of the clean reference paper (100 by definition); V is the volume sampled, in cubic metres; A is the area of
39、 the stain on the filter paper, in square metres. a A 2V -In R 0 R - =ISO9835:1993(E) BSI 07-1999 3 Key 1 Air intake 2 Filter clamp 3 Sampling pump 4 Dry gasmeter 5 Flow controller 6 Variable area flowmeter 7 Elapsed time meter Figure 1 Alternative sampling arrangements for black smoke measurementIS
40、O 9835:1993(E) 4 BSI 07-1999 6.2 Precision and accuracy The reflectance of filter stains can be read to1reflectance unit with 95% confidence. The resulting confidence limits for the absorption coefficient, a, are given inTable 1. Table 1 Confidence limits for absorption coefficients 7 Test report Th
41、e test report shall include the following information: a) a reference to this International Standard; b) a complete identification of the air sample, including date, time and location; c) the type of filter paper and reflectometer used; d) the results obtained, including the volume sampled, the samp
42、le duration, the flow rate and the measured reflectance (or absorbance); e) any unusual features noted during the determination; f) any operation carried out that is not specified in this International Standard; g) the location of any sources of black smoke close to the sampler which may have contri
43、buted to the results; h) any other information relevant to the method. Figure 2 Reflectometer response Reflectance, R a a Confidence limits % 10 5 %b % b 95 0,65 0,13 20,3 80 2,83 0,16 5,8 70 4,52 0,18 4,0 60 6,47 0,21 3,3 50 8,78 0,25 2,9 40 11,61 0,31 2,7 36 12,94 0,35 2,7 a For A = 5,07 10 4 m 2a
44、nd V = 2m 3ISO9835:1993(E) BSI 07-1999 5 Annex A (informative) Conversion of absorption coefficient to traditional black smoke units A.1 Basic theory For pure substances, the relationship between the extent of light absorption and the depth or thickness of the absorbing material is given by Lamberts
45、 Law, which states that equal fractions of the incident radiation are absorbed by successive layers of equal thickness of the light absorbing substance. This is represented mathematically by the equation where The absorption coefficient, a, refers to light of a particular wavelength and its value va
46、ries with the wavelength of the absorbed radiation. Thus, equation (A.1) represents the transmission and absorption of monochromatic radiation in a particular medium. A.2 The theory of reflectance measurement During sampling, air is drawn through a filter medium and the collected particles produce a
47、 stain on the surface of the filter paper. It is clear that most filter materials present a barrier to the radiation, therefore there can be no transmission of light and it is necessary to measure reflectance. Thus, to employ Lamberts Law (see equation A.1) it is necessary to assume that the surface
48、 of the filter material underlying the deposit acts as a perfect mirror and therefore the radiation passes through the absorbing layer twice. The staining power of the particulates on the surface is measured by comparing the stained surface with a blank, unexposed surface. The intensity of the incid
49、ent radiation, I 0 , and of the transmitted radiation, I, can be replaced by R 0and R, assuming that the reflectance, R 0 , of the unexposed filter material is analogous with the incident radiation, which is not actually measured. In fact, the difference between the incident radiation and the reflected radiation is due to scatter, which can be assumed to be the same for both blank and exposed filter papers and therefore ignored in terms of reflectance measurement. The
