1、BS ISO15767:2009ICS 13.040.30NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDWorkplaceatmospheres Controlling andcharacterizinguncertainty inweighing collectedaerosolsThis British Standardwas published under theauthority of the StandardsPolicy and StrategyCommit
2、tee on 31 July2009. BSI 2009ISBN 978 0 580 58086 4Amendments/corrigenda issued since publicationDate CommentsBS ISO 15767:2009National forewordThis British Standard is the UK implementation of ISO 15767:2009. Itsupersedes BS ISO 15767:2003 which is withdrawn.The UK participation in its preparation w
3、as entrusted to TechnicalCommittee EH/2/2, Work place atmospheres.A list of organizations 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
4、.Compliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 15767:2009Reference numberISO 15767:2009(E)ISO 2009INTERNATIONAL STANDARD ISO15767Second edition2009-06-01Workplace atmospheres Controlling and characterizing uncertainty in weighing collected aerosols Air des li
5、eux de travail Contrle et caractrisation de lincertitude de pese des arosols collects BS ISO 15767:2009ISO 15767:2009(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the type
6、faces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobes licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe S
7、ystems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlike
8、ly event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT ISO 2009 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
9、or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body 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
10、 www.iso.org Published in Switzerland ii ISO 2009 All rights reservedBS ISO 15767:2009ISO 15767:2009(E) ISO 2009 All rights reserved iiiContents Page Foreword iv Introduction.v 1 Scope1 2 Terms and definitions .1 3 Weight instability Causes and minimization3 3.1 General .3 3.2 Moisture sorption 3 3.
11、3 Electrostatic effects 4 3.4 Effects of volatile compounds (other than water)4 3.5 Handling damage.4 3.6 Buoyancy changes4 4 Correcting for weight instability by use of blanks.5 4.1 General .5 4.2 Minimum number of blanks5 4.3 Weighing times and sequence.5 4.4 Conditioning times 5 4.5 Storage stabi
12、lity.5 5 Transport of collection substrates with collected aerosol samples to laboratory.6 5.1 General .6 5.2 Recommended packaging6 6 Weighing equipment and procedure .6 6.1 The balance6 6.2 Recommended environmental controls7 6.3 Other equipment requirements7 6.4 Procedure.7 7 Recommendations for
13、the reporting of measured mass relative to LOD and LOQ .8 8 Estimation of the uncertainty of the analytical procedure of weighing aerosol collection substrates.8 8.1 Introduction8 8.2 Within-laboratory estimated standard deviation swobtained over an extended period 9 9 Measures to assure the validit
14、y of previously determined measurement uncertainty9 9.1 Continued determination of within-laboratory reproducibility.9 9.2 Participation in laboratory performance proficiency testing9 9.3 Laboratory self-check on weighing uncertainty 9 Annex A (normative) Uncertainty component in weighing collected
15、aerosol10 Annex B (informative) Interpretation of LOD and LOQ .14 Annex C (informative) Method evaluation example.16 Annex D (normative) Test of transportation integrity .17 Annex E (informative) Check on weighing uncertainty.18 Annex F (informative) Balance uncertainty19 Bibliography21 BS ISO 15767
16、:2009ISO 15767:2009(E) iv ISO 2009 All rights reservedForeword 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.
17、Each member body interested in a subject for which a technical 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 Internat
18、ional Electrotechnical Commission (IEC) on all matters of 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 Stand
19、ards 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. Attention is drawn to the possibility that some of the elements of this document may be the subjec
20、t of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 15767 was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 2, Workplace atmospheres. This second edition cancels and replaces the first edition (ISO 15767:2003), which has
21、 been technically revised. BS ISO 15767:2009ISO 15767:2009(E) ISO 2009 All rights reserved vIntroduction Assessment of airborne aerosol hazards in occupational settings entails sampling onto a collection substrate, followed by analysis of the collected material. The weight of the collection substrat
22、e is generally many times (10 to 20, or more) larger than the aerosol sample. Weighing the aerosol sample is therefore actually the differential weighing of the substrate, where the aerosol sample is essentially a disturbance of the substrate. The result is generally an estimated concentration of a
23、hazardous material in the air. The uncertainty in such estimates depends on several factors, one of which relates to the specific type of analysis employed. This International Standard deals with a specific type of analysis which finds the most general application in the sampling of aerosols, namely
24、 the weighing of sampled material. Gravimetric analysis, though apparently simple, is subject to uncertainty arising from instability in the mass of the sampling medium and other elements which must be weighed. An example is provided by aerosol samplers designed to collect particles so as to agree w
25、ith the inhalable aerosol sampling convention. For some sampler types, the filter and cassette are weighed together to make estimates. Therefore, uncertainty may result if the cassette, for example, absorbs or loses water between the weighings required for a concentration estimation. This Internatio
26、nal Standard describes such uncertainty and provides solutions for minimization. BS ISO 15767:2009BS ISO 15767:2009INTERNATIONAL STANDARD ISO 15767:2009(E) ISO 2009 All rights reserved 1Workplace atmospheres Controlling and characterizing uncertainty in weighing collected aerosols 1 Scope This Inter
27、national Standard provides recommendations for controlling the analytical uncertainty associated with aerosol collection medium instability, where collection medium or collection substrate includes any article used to collect particles (e.g. filter or foam material) as well as those supporting eleme
28、nts which must be analysed by weighing. This International Standard is applicable to results compiled both from the literature and, if necessary and feasible, through laboratory experiment. Expected uncertainty associated with given aerosol capture methods is quantified where possible. Recommendatio
29、ns as to materials to be used are given. Means of minimizing uncertainty arising from instability are provided. Recommendations for the weighing procedure are given. A procedure for estimating weighing uncertainty is described. Finally, recommendations are given for the reporting of measured mass, i
30、ncluding an uncertainty component and limits of detection and quantification. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 aerosol sample aerosol particles collected onto the collection substrate or sampling cassette 2.2 collection substra
31、te aerosol sampling filter, foam, impaction plate or other deposition plate designed for subsequent analysis, with whatever mounting, e.g. a sampling cassette, if used, analysed (weighed) as a single item together with the collected aerosol sample, if present NOTE As an example of the converse, the
32、25 mm or 37 mm plastic filter holder often used for “total dust” sampling in either its closed-face or open-face version is not part of the collection substrate in the definition above, since it is not weighed. 2.3 substrate holder cassette primarily designed to hold a collection substrate (of any k
33、ind) and for which only the deposit on the collection substrate is analysed (weighed) 2.4 filter holder substrate holder designed to hold a filter and for which only the filter deposit is analysed (weighed) 2.5 sampling cassette collection substrate together with whatever mounting that is used and a
34、nalysed (weighed) as a single unit BS ISO 15767:2009ISO 15767:2009(E) 2 ISO 2009 All rights reserved2.6 equilibration time time constant dependent on the type of collection substrate and characterizing an approximately exponentially damped approach of the mass of an aerosol collection medium to a co
35、nstant value NOTE 1 The constant can be defined as the mean difference of the mass from equilibrium per mean rate of mass loss or gain, averaging over any time interval. NOTE 2 There may be important instances in which several independent time constants are required to describe the approach to equil
36、ibrium. NOTE 3 Equilibration times range from seconds to weeks. 2.7 field blank blank collection substrate that undergoes the same handling as the collection substrate plus aerosol sample, including conditioning and loading into the samplers or transport containers, as well as transportation between
37、 the lab and sampling site, but without being exposed to sampling 2.8 lab blank blank collection substrate that never leaves the laboratory, but undergoes the same handling as the collection substrate plus aerosol sample, including conditioning and loading into the samplers or transport containers 2
38、.9 blank collection substrate collection medium or substrate taken from the same batch as the sampling medium, but unexposed to sampling 2.10 limit of detection LOD three times the estimated standard deviation of the mass of the aerosol sample, accounting for the double weighing (exposed vs. unexpos
39、ed) and for the uncertainty associated with any correction blanks used NOTE The value of LOD, as defined here, does not take into account sources of variability beyond weighing. 2.11 false positive rate fraction of incorrect assertions of the presence of an aerosol sample on a substrate NOTE Annex B
40、 describes how to estimate, on the basis of the method evaluation, the false positive rate in such assertions. 2.12 limit of quantification LOQ ten times the estimated standard deviation of the mass of the aerosol sample NOTE The value of LOQ can be used as a threshold value to assure accurate measu
41、rement of a substance. For details, see Annex B. 2.13 uncertainty component uwestimated standard deviation of the mass of the aerosol sample NOTE See Annex A and ISO/IEC Guide 98-3 for details. BS ISO 15767:2009ISO 15767:2009(E) ISO 2009 All rights reserved 33 Weight instability Causes and minimizat
42、ion 3.1 General Weight instability of collection substrates can be attributed to several causes (see References 1 to 14). The following subclauses address the more important of these. 3.2 Moisture sorption 3.2.1 Moisture sorption is the most common cause of weight instability. Water can be directly
43、collected by the filter or foam or other collection substrate material that is weighed. Water sorption by any part of the sampling system which is weighed must be suspected as well. For example, the sampling cassette itself, if weighed, can be the cause of significant uncertainty1. 3.2.2 The effects
44、 of water sorption can be reduced by using non-sorptive materials. However, there may exist specific sampling needs for which a hydrophobic material is not feasible. Table 1 presents a list of common aerosol collection substrates with different water sorption features. Table 1 Water sorption charact
45、eristics of some aerosol sampling media Water sorption Collection substrate or cassette type Very low Low High Very high Cellulose fibre filter * Glass fibre filter * Quartz fibre filter * Cellulose ester membrane filter * Polytetrafluoroethylene filter * PVC membrane filter * Polycarbonate filter *
46、 Silver membrane filter * Polyurethane foam * Greased Mylar impaction collection substrate * Greased aluminium foil impaction collection substrate * Carbon-filled resin * Aluminium cassette * Stainless steel cassette * NOTE 1 References 2 to 4 provide further details. Also, Reference 5 reports that
47、filters of evidently the same material, but originating from different manufacturers, can have widely differing variabilities. NOTE 2 There is generally a trade-off between hydrophobicity and conductivity in many materials 9. Therefore, one must be aware of the possibility of creating sampling probl
48、ems when reducing hygroscopicity. NOTE 3 Pre-treatments of collection substrates, such as greasing, can also affect water sorption. BS ISO 15767:2009ISO 15767:2009(E) 4 ISO 2009 All rights reserved3.3 Electrostatic effects Electrostatic effects are a common source of weighing problems. These effects
49、 can usually be minimized by discharging the collection substrate through the use of a plasma ion source or a radioactive source immediately before weighing or during weighing. Using conductive materials may reduce such problems. (See also Reference 7.) 3.4 Effects of volatile compounds (other than water) 3.4.1 Volatile compounds can be present in unused collection media3, or can be adsorbed onto media during sampling. 3.4.2 Desorption of volatiles from unused media can be controlled, for example, by h
