1、 ISO 2014 Air quality Determination of the number concentration of airborne inorganic fibres by phase contrast optical microscopy Membrane filter method Qualit de lair Dtermination de la concentration en nombre de fibres inorganiques en suspension dans lair par microscopie optique en contraste de ph
2、ase Mthode du filtre membrane INTERNATIONAL STANDARD ISO 8672 Second edition 2014-05-01 Reference number ISO 8672:2014(E) ISO 8672:2014(E)ii ISO 2014 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2014 All rights reserved. Unless otherwise specified, no part of this publication may be reproduc
3、ed or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. I
4、SO 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 ISO 8672:2014(E) ISO 2014 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 Terms
5、and definitions . 1 4 General method description 2 4.1 Limitations of the method by particle type 2 4.2 Limit of visibility and detection limits 2 4.3 Apparatus and equipment 3 4.4 Mounting media . 5 4.5 Quality assurance 6 5 Sampling 6 5.1 Flowrate 6 5.2 Acceptable fibre loadings on filters . 7 5.3
6、 Storage and transport . 7 5.4 Blanks . . 7 5.5 Sample duration and volume 8 5.6 Sampling strategy and records 9 6 Evaluation .10 6.1 Sample preparation .10 6.2 Microscope adjustment principles .11 6.3 Eyepiece graticule calibration .11 6.4 Microscope/counter performance assessment .11 6.5 Counting
7、and sizing fibres 12 6.6 Calculation of fibre concentration .13 7 Sources of errors and uncertainty 14 7.1 General 14 7.2 Uncertainty 14 7.3 Inter-laboratory variability .16 7.4 Lowering of intra- and inter-laboratory variance .17 8 Test report 17 Annex A (informative) Slide mounting: acetone-triace
8、tin procedure 19 Annex B (informative) Permanent slide preparation: dimethyl formamide - Euparal procedure .21 Annex C (normative) Eyepiece graticule 24 Annex D (informative) Measurement of exposed filter area 27 Annex E (informative) Microscope adjustment procedure 28 Annex F (informative) Sources
9、.29 Bibliography .30 ISO 8672:2014(E) Foreword 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
10、 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 International Electrotec
11、hnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO
12、 documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). 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 res
13、ponsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information giv
14、en for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the followi
15、ng URL: Foreword - Supplementary information The committee responsible for this document is ISO/TC 146, Air quality, Subcommittee SC 2, Workplace atmospheres. This second edition cancels and replaces the first edition (ISO 8672:1993), which has been technically revised. This second edition provides
16、additional quality assurance procedures.iv ISO 2014 All rights reserved ISO 8672:2014(E) Introduction The concentration of optically visible airborne inorganic fibres can only be defined in terms of the results obtained with a particular measurement method. Moreover, experience has shown that differ
17、ent laboratories, using the membrane filter optical counting method, can obtain different results on the same sample, even when the laboratories appear to be working from a written version of the method which attempts to specify all variables. Because of the unusual operator-dependence of the membra
18、ne filter method, it is important to apply this method with care and use it in conjunction with a quality control scheme. The second edition of this International Standard provides for additional quality assurance procedures. ISO 2014 All rights reserved v Air quality Determination of the number con
19、centration of airborne inorganic fibres by phase contrast optical microscopy Membrane filter method 1 Scope This International Standard specifies the determination of the number concentration of airborne inorganic fibres by phase contrast optical microscopy using the membrane filter method in workpl
20、ace atmospheres, as defined by the counting criteria given in 6.5.4. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated reference
21、s, the latest edition of the referenced document (including any amendments) applies. ISO 13137, Workplace atmospheres Pumps for personal sampling of chemical and biological agents Requirements and test methods 3 Terms and definitions For the purposes of this document, the following terms and definit
22、ions apply. NOTE Terms specific to this document are defined, in addition to those found in ASTM Standards D7200- 12, 6European Standard EN 1540. 7 3.1 reference slide slide prepared f rom a f ield sample by the acetone-triacetin method ( Annex A) or the dimethyl formamide- Euparal method (Annex B)
23、with a non-gridded cover slip that is to be used in a long-term quality control scheme Note 1 to entry: For the inventory of reference slides, they should be selected from a previous prepared bank of samples for which the mean and variability have been historically established. They should also comp
24、rise of samples with varying fibre densities, and if available different fibre types. Reference slides should be checked for filter integrity periodically and replaced if necessary. 3.2 breathing zone space around the nose and mouth from which a workers breath is taken Note 1 to entry: Technically,
25、the breathing zone corresponds to a hemisphere (generally accepted to be a 30 cm in radius) extending in front of the human face, centred on the mid-point of a line joining the ears. The base of the hemisphere is a plane through this line, the top of the head and the larynx. This technical descripti
26、on is not applicable when respiratory protective equipment is used. 7 3.3 countable fibre any object having a maximum width less than 3 m, an overall length greater than 5 m and a length to width ratio greater than 3:1. INTERNATIONAL ST ANDARD ISO 8672:2014(E) ISO 2014 All rights reserved 1 ISO 8672
27、:2014(E) 3.4 occupational exposure limit value limit of time-weighted average of the concentration of a chemical agent in the air within the breathing zone of a worker in relation to a specified reference period Note 1 to entry: Limit values are mostly set for reference periods of 8 h, but can also
28、be set for shorter periods or concentration excursions. Limit values for gases and vapours are stated in terms independent of temperature and air pressure variables in ml/m 3and in terms dependent on those variables in mg/ m 3for a temperature of 20 C and a pressure of 101,3 kPa. Limit values for ai
29、rborne particles and mixtures of particles and vapours are given in mg/m 3or multiples of that for actual environmental conditions (temperature, pressure) at the workplace. Limit values of fibres are given in numbers of fibres/m 3or number of fibres/cm 3for actual environmental conditions (temperatu
30、re, pressure) at the workplace. 7 4 General method description A sample is collected by drawing a measured quantity of air through a membrane filter by means of a battery-powered sampling pump. The entire filter or a portion of the filter (wedge) is later transformed from an opaque membrane into a h
31、omogeneous optically transparent specimen. The fibres are then sized and counted using a phase contrast optical microscope. The result is expressed as fibres per cubic centimetre of air, calculated from the number of fibres on the filter and the measured volume of air sampled. The method is applicab
32、le for routine sampling and sample evaluation necessary to assess personal exposure to fibres and implement control measures of their presence in occupational environments. The method is applicable for routine static sampling and measurement of personal exposure to fibres. 4.1 Limitations of the met
33、hod by particle type This method cannot identify the composition or characteristics of particular fibre types and its use shall be restricted to workplace atmospheres where the predominant fibre types are inorganic. The use of this method also has limitations when applied to samples containing platy
34、 or acicular particles and consequently it should not be implemented without prior knowledge of the fibres present in the workplace atmosphere. There are a variety of analytical methods which can be useful, e.g. polarizing light microscopy, electron microscopy. 4.2 Limit of visibility and detection
35、limits This procedure cannot enumerate thin fibres whose width is below the limit of visibilty by phase contrast optical microscopy. The limit varies according to the refractive index contrast between the fibres and the mounting medium, and the phase-shift of the microscope. The triacetin mounting m
36、edium proposed in this method has a refractive index of approximately 1,45, and the Euparal mounting medium has a refractive index of 1,48. In workplace atmospheres, fibres with refractive indices in the range of 1,4 to 1,5 might occur. As the relatively small refractive index difference between the
37、se fibres and the mounting media might not be sufficient for them to be visible, this mounting media might not be appropriate. Previously published method limitations of 0,2 m or 0,25 m width limits are conservative consensus values. Practical studies have indicated the ability of a microscope prope
38、rly adjusted to detect chrysotile fibres of 0,15 m width 11and Amosite fibres of 0,062 5 m width. 12These results suggest crocidolite fibres can be detectable at 0,05 m width. Fibres with smaller widths can be detected under the electron microscope, but large differences in results sometimes observe
39、d between the two methods are more likely due to undercounting fine fibres under phase contrast microscopy (PCM) than to the presence of substantial numbers of fibres that can only be seen under the electron microscope. The quality assurance procedures in this International Standard are used to iden
40、tify and resolve several types of counting errors under PCM. With the parameters specified in this method, the theoretical lower detection limit for a sample of 480 l of air is 0,007 fibres/cm 3 . However, the limit of practical use is often 0,1 fibres/cm 3or higher. This is because blank filters ca
41、n frequently give a reading of several countable fibres per 100 graticule areas. These “fibres” are contaminants on the filter, or artefacts from the clearing process which have the 2 ISO 2014 All rights reserved ISO 8672:2014(E) appearance of fibres. Neither counting more fields nor increasing samp
42、ling duration overcomes the problem of background dust, when fibres are a minor constituent of the dust cloud. In relatively clean atmospheres, such as cleaned enclosure after asbestos removal (clearance sampling), the expected fibre concentration is 480 l) are required to achieve quantifiable loadi
43、ngs. 4.3 Apparatus and equipment 4.3.1 Sampling equipment 4.3.1.1 Filters. Membrane filters (mixed cellulose ester or cellulose nitrate) of 0,8 to 1,2 m or less pore size and a diameter of 25 mm are preferred with, or without printed grids (printed grids can allow the counter to focus easier on the
44、plane containing the fibres, but the lines of the grid can obstruct all or parts of the fields of view and interfere with the counting so that these fields must be avoided). In recent years, problems have been observed with portions of batches of mixed cellulose ester filters, where the porosity is
45、not evenly developed over the filter. Areas of the filter without porosity can lead to a high pressure drop resulting in premature pump failure, areas of the filter without fibres deposited, and the appearance of cracking in acetone-triacetin mounts. 13It is necessary to pay attention to the quality
46、 of filters in order to avoid these problems. In addition, each batch of filters should be tested for fibrous contamination as described in 5.4. 4.3.1.2 Open-faced filter holder fitted with a protective cowl. 14The distance between the cowl opening and the filter plane should be between one and a ha
47、lf times and two times the internal diameter of the cowl. The internal diameter of the cowl should be at least equal to the exposed diameter of the filter but not more than 2 mm greater. The cowl helps to protect the filter from accidental contamination. A conducting cowl is preferred to a plastic o
48、ne because of the possible risk of fibre loss due to electrostatic charge. Filter holders and cowls shall be thoroughly washed before re-use. Due to the design of the filter support utilized in some filter holders, a supporting pad should be used. The purpose of this supporting pad is to ensure an e
49、ven distribution of air passing through the primary membrane. 4.3.1.3 Sampling pump, capable of giving a smooth flow and having flow set to within 5 % of the required flowrate, and of maintaining this flowrate through the filter to within 10 % for flowrate 2 l/min and 5 % for flowrate 2 l/min during the period of sampling. Although some pumps are equipped with pulsation dampers, an external damper might have to be installed between the pump and the collecting media. Personal sampling pumps shall meet the criteri
