Ambient air - Determination of asbestos fibres - Indirect-transfer transmission electron microscopy method

This document specifies a reference method using transmission electron microscopy for the determination of airborne asbestos fibres and structures in in a wide range of ambient air situations, including the interior atmospheres of buildings, and for a detailed evaluation for asbestos structures in any atmosphere. The specimen preparation procedure incorporates ashing and dispersion of the collected particulate, so that all asbestos is measured, including the asbestos originally incorporated in particle aggregates or particles of composite materials. The lengths, widths and aspect ratios of the asbestos fibres and bundles are measured, and these, together with the density of the type of asbestos, also allow the total mass concentration of airborne asbestos to be calculated. The method allows determination of the type(s) of asbestos fibres present. The method cannot discriminate between individual fibres of the asbestos and elongate fragments (cleavage fragments and acicular particles) from non-asbestos analogues of the same amphibole mineral[12].

Air ambiant - Dosage des fibres d'amiante - Méthode par microscopie électronique à transmission par transfert indirect

Le pr�sent document sp�cifie une m�thode de r�f�rence utilisant la microscopie �lectronique � transmission pour la d�termination de la concentration en fibres et structures d'amiante en suspension dans l'air dans les atmosph�res ambiantes, notamment les atmosph�res int�rieures de b�timents, et pour l'�valuation d�taill�e des structures d'amiante dans les atmosph�res. Le mode op�ratoire de pr�paration des �chantillons comprend la calcination et la dispersion des particules recueillies, de sorte que la totalit� de l'amiante est mesur�e, y compris l'amiante initialement incorpor�e dans les agr�gats particulaires ou les particules de mat�riaux composites. Les longueurs, largeurs et rapports longueur/largeur des fibres et faisceaux d'amiante sont mesur�s. Ils permettent �galement, conjointement avec la densit� du type d'amiante, de calculer la concentration massique totale d'amiante en suspension dans l'air. La m�thode permet de d�terminer le(s) type(s) de fibres d'amiante pr�sentes. La m�thode ne peut pas faire la diff�rence entre les fibres individuelles d'amiante amphibole et fragments allong�s (fragments de clivage et particules aciculaires) et les analogues non asbestiformes du m�me min�ral amphibole[12].

Zunanji zrak - Določevanje azbestnih vlaken - Metoda transmisijske elektronske mikroskopije s posrednim prenosom

Ta dokument določa referenčno metodo, pri kateri se s prenosno elektronsko mikroskopijo določajo azbestna vlakna in strukture v zraku v najrazličnejših okoliščinah zunanjega zraka, vključno z notranjo atmosfero stavb, ter za podrobno oceno azbestnih struktur v poljubni atmosferi. Postopek priprave vzorca vključuje upepelitev in razpršitev zbranih delcev, tako da se izmeri ves azbest, vključno z azbestom, ki je bil prvotno vgrajen v agregat delcev ali delce kompozitnih materialov. Izmerijo se dolžine, širine in razmerja azbestnih vlaken in svežnjev, kar skupaj z gostoto vrste azbesta omogoča tudi izračun skupne masne koncentracije azbesta v zraku. Metoda omogoča določitev vrst(-e) prisotnih azbestnih vlaken. Z metodo ni mogoče razlikovati med posameznimi vlakni azbesta in razteznimi fragmenti (delci cepitve in acikularnimi delci) iz neazbestnih analogov istega amfibolovega minerala[12].

General Information

Status
Published
Public Enquiry End Date
09-Oct-2018
Publication Date
10-Nov-2019
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
04-Nov-2019
Due Date
09-Jan-2020
Completion Date
11-Nov-2019

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INTERNATIONAL ISO
STANDARD 13794
Second edition
2019-10
Ambient air — Determination of
asbestos fibres — Indirect-transfer
transmission electron microscopy
method
Air ambiant — Dosage des fibres d'amiante — Méthode par
microscopie électronique à transmission par transfert indirect
Reference number
ISO 13794:2019(E)
ISO 2019
---------------------- Page: 1 ----------------------
ISO 13794:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced 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 ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 13794:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................vi

Introduction ..............................................................................................................................................................................................................................vii

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 7

5 Type of sample ........................................................................................................................................................................................................ 8

6 Range ................................................................................................................................................................................................................................ 8

7 Limit of detection ................................................................................................................................................................................................. 8

8 Principle ........................................................................................................................................................................................................................ 8

9 Reagents ........................................................................................................................................................................................................................ 9

10 Apparatus ..................................................................................................................................................................................................................10

10.1 Air sampling ...........................................................................................................................................................................................10

10.1.1 Filter cassette ...................................................................................................................................................................10

10.1.2 Sampling pump ..............................................................................................................................................................10

10.1.3 Stand ........................................................................................................................................................................................10

10.1.4 Personal sampling .......................................................................................................................................................10

10.1.5 Flowmeter ..........................................................................................................................................................................10

10.2 Specimen preparation laboratory .......................................................................................................................................11

10.3 Equipment for analysis .................................................................................................................................................................11

10.3.1 Transmission electron microscope ...............................................................................................................11

10.3.2 Energy dispersive X-ray analyser ...................................................................................................................13

10.3.3 Plasma asher ....................................................................................................................................................................13

10.3.4 Vacuum coating unit ..................................................................................................................................................13

10.3.5 Sputter coater ..................................................................................................................................................................13

10.3.6 Beakers ..................................................................................................................................................................................13

10.3.7 Vacuum source ................................................................................................................................................................13

10.3.8 Glass filtration apparatus ......................................................................................................................................14

10.3.9 Solvent washer (Jaffe washer) ..........................................................................................................................14

10.3.10 Condensation washer ...............................................................................................................................................15

10.3.11 Slide warmer or oven ................................................................................................................................................16

10.3.12 Ultrasonic bath ...............................................................................................................................................................16

10.3.13 Carbon grating replica..............................................................................................................................................16

10.3.14 Calibration specimen grids for EDXA ..........................................................................................................16

10.3.15 Carbon rod sharpener ..............................................................................................................................................17

10.3.16 Disposable tip micropipettes .............................................................................................................................17

10.3.17 Thermometer ...................................................................................................................................................................17

10.3.18 Stopwatch............................................................................................................................................................................17

10.4 Consumable supplies ......................................................................................................................................................................17

10.4.1 Copper or nickel electron microscope grids .........................................................................................17

10.4.2 Gold or nickel electron microscope grids ................................................................................................17

10.4.3 Aluminium foil ................................................................................................................................................................17

10.4.4 Carbon rod electrodes ..............................................................................................................................................17

10.4.5 Routine electron microscopy tools and supplies. .............................................................................18

10.4.6 Reference asbestos samples .................. ..............................................................................................................18

10.4.7 Reference samples of mineral fibres other than asbestos ........................................................18

11 Air sample collection ....................................................................................................................................................................................18

11.1 Calculation of analytical sensitivity ....................................................................................................................................18

11.2 Sample collection procedure ...................................................................................................................................................19

© ISO 2019 – All rights reserved iii
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ISO 13794:2019(E)

12 Procedure for analysis .................................................................................................................................................................................20

12.1 General ........................................................................................................................................................................................................20

12.2 Cleaning of sample cassettes ...................................................................................................................................................20

12.3 Preparation of analytical filters .............................................................................................................................................20

12.3.1 Selection of filter area for ashing ....................................................................................................................20

12.3.2 Ashing of sample collection filters.................................................................................................................20

12.3.3 Aqueous dispersal of residual ash from sample collection filters ......................................21

12.3.4 Assembly of system for filtration of aqueous dispersions ........................................................21

12.3.5 Filtration of aqueous dispersions...................................................................................................................21

12.4 Preparation of TEM specimens from PC analytical filters ..............................................................................22

12.4.1 Selection of filter area for carbon-coating ..............................................................................................22

12.4.2 Carbon-coating of filter portions ....................................................................................................................22

12.4.3 Preparation of the Jaffe washer ........................................................................................................................23

12.4.4 Placing of specimens into the Jaffe washer ............................................................................................23

12.5 Preparation of TEM specimens from cellulose ester analytical filters ................................................23

12.5.1 Selection of area of filter for preparation ................................................................................................23

12.5.2 Preparation of solution for collapsing cellulose ester filters ..................................................23

12.5.3 Filter-collapsing procedure .................................................................................................................................23

12.5.4 Plasma etching of the filter surface ..............................................................................................................23

12.5.5 Carbon-coating ...............................................................................................................................................................24

12.5.6 Preparation of the Jaffe washer ........................................................................................................................24

12.5.7 Placing of specimens in the Jaffe washer .................................................................................................24

12.6 Criteria for acceptable TEM specimen grids ..............................................................................................................24

12.7 Procedure for structure counting by TEM....................................................................................................................25

12.7.1 General...................................................................................................................................................................................25

12.7.2 Measurement of mean grid opening area ...............................................................................................25

12.7.3 TEM alignment and calibration procedures ..........................................................................................26

12.7.4 Determination of criterion for termination of TEM examination.......................................26

12.7.5 General procedure for structure counting and size analysis ..................................................26

12.7.6 Estimation of mass concentration of asbestos fibres and bundles ...................................27

12.7.7 Magnification requirements ...............................................................................................................................27

12.8 Blank and quality control determinations ...................................................................................................................29

12.9 Calculation of results ......................................................................................................................................................................30

13 Performance characteristics .................................................................................................................................................................30

13.1 General ........................................................................................................................................................................................................30

13.2 Interferences and limitations of fibre identification ...........................................................................................30

13.3 Precision and accuracy..................................................................................................................................................................31

13.3.1 Precision...............................................................................................................................................................................31

13.3.2 Accuracy ...............................................................................................................................................................................31

13.3.3 Inter- and intra-laboratory analyses ...........................................................................................................31

13.4 Limit of detection ...............................................................................................................................................................................32

14 Test report ................................................................................................................................................................................................................32

Annex A (normative) Determination of operating conditions for plasma asher ................................................36

Annex B (normative) Determination and standardization of operating conditions for

ultrasonic bath .....................................................................................................................................................................................................37

Annex C (normative) Calibration procedures ..........................................................................................................................................39

Annex D (normative) Structure counting criteria ...............................................................................................................................42

Annex E (normative) Fibre identification procedure ......................................................................................................................52

Annex F (normative) Determination of the concentration of asbestos fibres and bundles

longer than 5 µm and PCM equivalent asbestos fibres ..............................................................................................68

Annex G (normative) Calculation of results ...............................................................................................................................................69

Annex H (normative) Test procedure to determine suitability of cellulose ester sample

collection filters ..................................................................................................................................................................................................76

iv © ISO 2019 – All rights reserved
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ISO 13794:2019(E)

Annex I (informative) Strategies for collection of air samples ...............................................................................................77

Bibliography .............................................................................................................................................................................................................................78

© ISO 2019 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO 13794:2019(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 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 Electrotechnical 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 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 responsible 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 given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www .iso .org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 3,

Ambient atmospheres.

This second edition cancels and replaces the first edition (ISO 13794:1999), which has been technically

revised. The main changes compared to the previous edition are as follows:
— the use of electronic display systems with measurement software is permitted;

— the maximum particulate loading for TEM specimens is increased from 10 % to 25 %;

— a simplified fibre identification procedure for investigation of known sources of the regulated

asbestos varieties and richterite/winchite asbestos is permitted;

— the reporting requirements have been changed to permit reporting of the concentrations of fibres

and bundles longer than 5 µm and/or the concentrations of PCM equivalent fibres without the

requirement to report the concentrations of structures equal to or greater than 0,5 µm;

— there is no requirement to report the 95 % confidence intervals of the fibre concentrations.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
vi © ISO 2019 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 13794:2019(E)
Introduction

This document is applicable to the measurement of airborne asbestos in a wide range of ambient

air situations, including the interior atmospheres of buildings, and for a detailed evaluation of

any atmosphere. Because the best available medical evidence indicates that the numerical fibre

concentration and the fibre size and type are the relevant parameters for evaluation of the inhalation

hazards, a fibre counting and measuring technique is the only logical approach. Most fibres in ambient

atmospheres are not asbestos, and therefore there is a requirement for fibres to be identified. Many

airborne asbestos fibres in ambient atmospheres have diameters below the resolution limit of the

optical microscope. This document is based on transmission electron microscopy, which has adequate

resolution to allow for the detection of small fibres and is currently the only technique capable of

unequivocal identification of the majority of individual fibres of asbestos. The fibres found suspended

in an ambient atmosphere can often be identified unequivocally, if sufficient measurement effort is

expended. However, if each fibre were to be identified in this way, the analysis becomes prohibitively

expensive. Because of instrumental deficiencies or because of the nature of the particulate, some

fibres cannot be positively identified as asbestos, even though the measurements all indicate that they

could be asbestos. Subjective and instrumental factors therefore contribute to this measurement, and

consequently a very precise definition of the procedure for identification and enumeration of asbestos

fibres is required.

In addition to single fibres and bundles, asbestos is often found in air samples as very complex,

aggregated structures, which may or may not be also aggregated with other particles. The number

of asbestos fibres and bundles incorporated in these complex structures often exceeds the number

of isolated fibres and bundles observed, and many of them may be completely obscured in direct-

transfer transmission electron microscope (TEM) preparations. The method defined in this document

incorporates specimen preparation procedures that result in the selective concentration of asbestos

fibres and the removal of organic, water-soluble and acid-soluble materials. These procedures have the

effect of dispersing the majority of the complex clusters and aggregates of fibres into their component

fibres and bundles so that the asbestos in the air sample can be more accurately quantified. All of the

feasible specimen preparation techniques result in some modification of the airborne particulate. Even

the collection of particles from a three-dimensional airborne dispersion on to a two-dimensional filter

surface can be considered a modification of the particulate, and some of the particles in most samples

are modified by the specimen preparation procedures. Although this method results in dispersal of

complex clusters and aggregates, it minimizes other effects on the size distribution of fibres and fibre

bundles.

This document requires a very detailed and logical procedure is used to reduce the subjective aspects

of the measurement. The method of data recording specified in the document is designed to allow re-

evaluation of the fibre counting data as new medical evidence becomes available.

This document describes the method of analysis for a single air filter. However, one of the largest

potential errors in characterizing asbestos in ambient atmospheres is associated with the variability

between filter samples. For this reason, it is necessary to design a replicate sampling scheme in order to

determine the standard's accuracy and precision.

Comparison of results obtained using this indirect-transfer procedure with those from the direct-

transfer procedure cannot be done a priori. This can only be achieved by a site-specific inter-comparison

study that takes into account the fibre size and type of asbestos, and also the nature of the source of the

airborne asbestos.
© ISO 2019 – All rights reserved vii
---------------------- Page: 7 ----------------------
INTERNATIONAL STANDARD ISO 13794:2019(E)
Ambient air — Determination of asbestos fibres — Indirect-
transfer transmission electron microscopy method
1 Scope

This document specifies a reference method using transmission electron microscopy for the

determination of airborne asbestos fibres and structures in in a wide range of ambient air situations,

including the interior atmospheres of buildings, and for a detailed evaluation for asbestos structures

in any atmosphere. The specimen preparation procedure incorporates ashing and dispersion of the

collected particulate, so that all asbestos is measured, including the asbestos originally incorporated

in particle aggregates or particles of composite materials. The lengths, widths and aspect ratios of the

asbestos fibres and bundles are measured, and these, together with the density of the type of asbestos,

also allow the total mass concentration of airborne asbestos to be calculated. The method allows

determination of the type(s) of asbestos fibres present. The method cannot discriminate between

individual fibres of the asbestos and elongate fragments (cleavage fragments and acicular particles)

[12]
from non-asbestos analogues of the same amphibole mineral .
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 4225, Air quality — General aspects — Vocabulary
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 4225 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
acicular

shape shown by an extremely slender crystal with cross-sectional dimensions which are small relative

to its length, i.e. needle-like
[SOURCE: ISO 10312:1995, 3.1]
3.2
amphibole

group of rock-forming ferromagnesium silicate minerals, closely related in crystal form and

composition, and having the nominal formula:
A B C T O (OH,F,Cl)
0-1 2 5 8 22 2
where
© ISO 2019 – All rights reserved 1
---------------------- Page: 8 ----------------------
ISO 13794:2019(E)
A is K, Na;
B is Fe , Mn, Mg, Ca, Na;
3+ 2+
C is Al, Cr, Ti, Fe , Mg, Fe ;
T is Si, Al, Cr, Fe , Ti.

Note 1 to entry: In some varieties of amphibole, these elements can be partially substituted by Li, Pb, or Zn.

Amphibole is characterized by a cross-linked double chain of Si-O tetrahedra with a silicon: oxygen ratio of 4:11,

by columnar or fibrous prismatic crystals and by good prismatic cleavage in two directions parallel to the crystal

faces and intersecting at angles
...

SLOVENSKI STANDARD
SIST ISO 13794:2019
01-december-2019
Nadomešča:
SIST ISO 13794:2002
Zunanji zrak - Določevanje azbestnih vlaken - Metoda transmisijske elektronske
mikroskopije s posrednim prenosom

Ambient air - Determination of asbestos fibres - Indirect-transfer transmission electron

microscopy method

Air ambiant - Dosage des fibres d'amiante - Méthode par microscopie électronique à

transmission par transfert indirect
Ta slovenski standard je istoveten z: ISO 13794:2019
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
SIST ISO 13794:2019 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST ISO 13794:2019
---------------------- Page: 2 ----------------------
SIST ISO 13794:2019
INTERNATIONAL ISO
STANDARD 13794
Second edition
2019-10
Ambient air — Determination of
asbestos fibres — Indirect-transfer
transmission electron microscopy
method
Air ambiant — Dosage des fibres d'amiante — Méthode par
microscopie électronique à transmission par transfert indirect
Reference number
ISO 13794:2019(E)
ISO 2019
---------------------- Page: 3 ----------------------
SIST ISO 13794:2019
ISO 13794:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced 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 ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 13794:2019
ISO 13794:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................vi

Introduction ..............................................................................................................................................................................................................................vii

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 7

5 Type of sample ........................................................................................................................................................................................................ 8

6 Range ................................................................................................................................................................................................................................ 8

7 Limit of detection ................................................................................................................................................................................................. 8

8 Principle ........................................................................................................................................................................................................................ 8

9 Reagents ........................................................................................................................................................................................................................ 9

10 Apparatus ..................................................................................................................................................................................................................10

10.1 Air sampling ...........................................................................................................................................................................................10

10.1.1 Filter cassette ...................................................................................................................................................................10

10.1.2 Sampling pump ..............................................................................................................................................................10

10.1.3 Stand ........................................................................................................................................................................................10

10.1.4 Personal sampling .......................................................................................................................................................10

10.1.5 Flowmeter ..........................................................................................................................................................................10

10.2 Specimen preparation laboratory .......................................................................................................................................11

10.3 Equipment for analysis .................................................................................................................................................................11

10.3.1 Transmission electron microscope ...............................................................................................................11

10.3.2 Energy dispersive X-ray analyser ...................................................................................................................13

10.3.3 Plasma asher ....................................................................................................................................................................13

10.3.4 Vacuum coating unit ..................................................................................................................................................13

10.3.5 Sputter coater ..................................................................................................................................................................13

10.3.6 Beakers ..................................................................................................................................................................................13

10.3.7 Vacuum source ................................................................................................................................................................13

10.3.8 Glass filtration apparatus ......................................................................................................................................14

10.3.9 Solvent washer (Jaffe washer) ..........................................................................................................................14

10.3.10 Condensation washer ...............................................................................................................................................15

10.3.11 Slide warmer or oven ................................................................................................................................................16

10.3.12 Ultrasonic bath ...............................................................................................................................................................16

10.3.13 Carbon grating replica..............................................................................................................................................16

10.3.14 Calibration specimen grids for EDXA ..........................................................................................................16

10.3.15 Carbon rod sharpener ..............................................................................................................................................17

10.3.16 Disposable tip micropipettes .............................................................................................................................17

10.3.17 Thermometer ...................................................................................................................................................................17

10.3.18 Stopwatch............................................................................................................................................................................17

10.4 Consumable supplies ......................................................................................................................................................................17

10.4.1 Copper or nickel electron microscope grids .........................................................................................17

10.4.2 Gold or nickel electron microscope grids ................................................................................................17

10.4.3 Aluminium foil ................................................................................................................................................................17

10.4.4 Carbon rod electrodes ..............................................................................................................................................17

10.4.5 Routine electron microscopy tools and supplies. .............................................................................18

10.4.6 Reference asbestos samples .................. ..............................................................................................................18

10.4.7 Reference samples of mineral fibres other than asbestos ........................................................18

11 Air sample collection ....................................................................................................................................................................................18

11.1 Calculation of analytical sensitivity ....................................................................................................................................18

11.2 Sample collection procedure ...................................................................................................................................................19

© ISO 2019 – All rights reserved iii
---------------------- Page: 5 ----------------------
SIST ISO 13794:2019
ISO 13794:2019(E)

12 Procedure for analysis .................................................................................................................................................................................20

12.1 General ........................................................................................................................................................................................................20

12.2 Cleaning of sample cassettes ...................................................................................................................................................20

12.3 Preparation of analytical filters .............................................................................................................................................20

12.3.1 Selection of filter area for ashing ....................................................................................................................20

12.3.2 Ashing of sample collection filters.................................................................................................................20

12.3.3 Aqueous dispersal of residual ash from sample collection filters ......................................21

12.3.4 Assembly of system for filtration of aqueous dispersions ........................................................21

12.3.5 Filtration of aqueous dispersions...................................................................................................................21

12.4 Preparation of TEM specimens from PC analytical filters ..............................................................................22

12.4.1 Selection of filter area for carbon-coating ..............................................................................................22

12.4.2 Carbon-coating of filter portions ....................................................................................................................22

12.4.3 Preparation of the Jaffe washer ........................................................................................................................23

12.4.4 Placing of specimens into the Jaffe washer ............................................................................................23

12.5 Preparation of TEM specimens from cellulose ester analytical filters ................................................23

12.5.1 Selection of area of filter for preparation ................................................................................................23

12.5.2 Preparation of solution for collapsing cellulose ester filters ..................................................23

12.5.3 Filter-collapsing procedure .................................................................................................................................23

12.5.4 Plasma etching of the filter surface ..............................................................................................................23

12.5.5 Carbon-coating ...............................................................................................................................................................24

12.5.6 Preparation of the Jaffe washer ........................................................................................................................24

12.5.7 Placing of specimens in the Jaffe washer .................................................................................................24

12.6 Criteria for acceptable TEM specimen grids ..............................................................................................................24

12.7 Procedure for structure counting by TEM....................................................................................................................25

12.7.1 General...................................................................................................................................................................................25

12.7.2 Measurement of mean grid opening area ...............................................................................................25

12.7.3 TEM alignment and calibration procedures ..........................................................................................26

12.7.4 Determination of criterion for termination of TEM examination.......................................26

12.7.5 General procedure for structure counting and size analysis ..................................................26

12.7.6 Estimation of mass concentration of asbestos fibres and bundles ...................................27

12.7.7 Magnification requirements ...............................................................................................................................27

12.8 Blank and quality control determinations ...................................................................................................................29

12.9 Calculation of results ......................................................................................................................................................................30

13 Performance characteristics .................................................................................................................................................................30

13.1 General ........................................................................................................................................................................................................30

13.2 Interferences and limitations of fibre identification ...........................................................................................30

13.3 Precision and accuracy..................................................................................................................................................................31

13.3.1 Precision...............................................................................................................................................................................31

13.3.2 Accuracy ...............................................................................................................................................................................31

13.3.3 Inter- and intra-laboratory analyses ...........................................................................................................31

13.4 Limit of detection ...............................................................................................................................................................................32

14 Test report ................................................................................................................................................................................................................32

Annex A (normative) Determination of operating conditions for plasma asher ................................................36

Annex B (normative) Determination and standardization of operating conditions for

ultrasonic bath .....................................................................................................................................................................................................37

Annex C (normative) Calibration procedures ..........................................................................................................................................39

Annex D (normative) Structure counting criteria ...............................................................................................................................42

Annex E (normative) Fibre identification procedure ......................................................................................................................52

Annex F (normative) Determination of the concentration of asbestos fibres and bundles

longer than 5 µm and PCM equivalent asbestos fibres ..............................................................................................68

Annex G (normative) Calculation of results ...............................................................................................................................................69

Annex H (normative) Test procedure to determine suitability of cellulose ester sample

collection filters ..................................................................................................................................................................................................76

iv © ISO 2019 – All rights reserved
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SIST ISO 13794:2019
ISO 13794:2019(E)

Annex I (informative) Strategies for collection of air samples ...............................................................................................77

Bibliography .............................................................................................................................................................................................................................78

© ISO 2019 – All rights reserved v
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SIST ISO 13794:2019
ISO 13794:2019(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 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 Electrotechnical 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 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 responsible 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 given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www .iso .org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 3,

Ambient atmospheres.

This second edition cancels and replaces the first edition (ISO 13794:1999), which has been technically

revised. The main changes compared to the previous edition are as follows:
— the use of electronic display systems with measurement software is permitted;

— the maximum particulate loading for TEM specimens is increased from 10 % to 25 %;

— a simplified fibre identification procedure for investigation of known sources of the regulated

asbestos varieties and richterite/winchite asbestos is permitted;

— the reporting requirements have been changed to permit reporting of the concentrations of fibres

and bundles longer than 5 µm and/or the concentrations of PCM equivalent fibres without the

requirement to report the concentrations of structures equal to or greater than 0,5 µm;

— there is no requirement to report the 95 % confidence intervals of the fibre concentrations.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
vi © ISO 2019 – All rights reserved
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SIST ISO 13794:2019
ISO 13794:2019(E)
Introduction

This document is applicable to the measurement of airborne asbestos in a wide range of ambient

air situations, including the interior atmospheres of buildings, and for a detailed evaluation of

any atmosphere. Because the best available medical evidence indicates that the numerical fibre

concentration and the fibre size and type are the relevant parameters for evaluation of the inhalation

hazards, a fibre counting and measuring technique is the only logical approach. Most fibres in ambient

atmospheres are not asbestos, and therefore there is a requirement for fibres to be identified. Many

airborne asbestos fibres in ambient atmospheres have diameters below the resolution limit of the

optical microscope. This document is based on transmission electron microscopy, which has adequate

resolution to allow for the detection of small fibres and is currently the only technique capable of

unequivocal identification of the majority of individual fibres of asbestos. The fibres found suspended

in an ambient atmosphere can often be identified unequivocally, if sufficient measurement effort is

expended. However, if each fibre were to be identified in this way, the analysis becomes prohibitively

expensive. Because of instrumental deficiencies or because of the nature of the particulate, some

fibres cannot be positively identified as asbestos, even though the measurements all indicate that they

could be asbestos. Subjective and instrumental factors therefore contribute to this measurement, and

consequently a very precise definition of the procedure for identification and enumeration of asbestos

fibres is required.

In addition to single fibres and bundles, asbestos is often found in air samples as very complex,

aggregated structures, which may or may not be also aggregated with other particles. The number

of asbestos fibres and bundles incorporated in these complex structures often exceeds the number

of isolated fibres and bundles observed, and many of them may be completely obscured in direct-

transfer transmission electron microscope (TEM) preparations. The method defined in this document

incorporates specimen preparation procedures that result in the selective concentration of asbestos

fibres and the removal of organic, water-soluble and acid-soluble materials. These procedures have the

effect of dispersing the majority of the complex clusters and aggregates of fibres into their component

fibres and bundles so that the asbestos in the air sample can be more accurately quantified. All of the

feasible specimen preparation techniques result in some modification of the airborne particulate. Even

the collection of particles from a three-dimensional airborne dispersion on to a two-dimensional filter

surface can be considered a modification of the particulate, and some of the particles in most samples

are modified by the specimen preparation procedures. Although this method results in dispersal of

complex clusters and aggregates, it minimizes other effects on the size distribution of fibres and fibre

bundles.

This document requires a very detailed and logical procedure is used to reduce the subjective aspects

of the measurement. The method of data recording specified in the document is designed to allow re-

evaluation of the fibre counting data as new medical evidence becomes available.

This document describes the method of analysis for a single air filter. However, one of the largest

potential errors in characterizing asbestos in ambient atmospheres is associated with the variability

between filter samples. For this reason, it is necessary to design a replicate sampling scheme in order to

determine the standard's accuracy and precision.

Comparison of results obtained using this indirect-transfer procedure with those from the direct-

transfer procedure cannot be done a priori. This can only be achieved by a site-specific inter-comparison

study that takes into account the fibre size and type of asbestos, and also the nature of the source of the

airborne asbestos.
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SIST ISO 13794:2019
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SIST ISO 13794:2019
INTERNATIONAL STANDARD ISO 13794:2019(E)
Ambient air — Determination of asbestos fibres — Indirect-
transfer transmission electron microscopy method
1 Scope

This document specifies a reference method using transmission electron microscopy for the

determination of airborne asbestos fibres and structures in in a wide range of ambient air situations,

including the interior atmospheres of buildings, and for a detailed evaluation for asbestos structures

in any atmosphere. The specimen preparation procedure incorporates ashing and dispersion of the

collected particulate, so that all asbestos is measured, including the asbestos originally incorporated

in particle aggregates or particles of composite materials. The lengths, widths and aspect ratios of the

asbestos fibres and bundles are measured, and these, together with the density of the type of asbestos,

also allow the total mass concentration of airborne asbestos to be calculated. The method allows

determination of the type(s) of asbestos fibres present. The method cannot discriminate between

individual fibres of the asbestos and elongate fragments (cleavage fragments and acicular particles)

[12]
from non-asbestos analogues of the same amphibole mineral .
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 4225, Air quality — General aspects — Vocabulary
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 4225 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www
...

NORME ISO
INTERNATIONALE 13794
Deuxième édition
2019-10
Air ambiant — Dosage des fibres
d'amiante — Méthode par microscopie
électronique à transmission par
transfert indirect
Ambient air — Determination of asbestos fibres — Indirect-transfer
transmission electron microscopy method
Numéro de référence
ISO 13794:2019(F)
ISO 2019
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ISO 13794:2019(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2019

Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette

publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,

y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut

être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.

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Publié en Suisse
ii © ISO 2019 – Tous droits réservés
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ISO 13794:2019(F)
Sommaire Page

Avant-propos ..............................................................................................................................................................................................................................vi

Introduction ..............................................................................................................................................................................................................................vii

1 Domaine d’application ................................................................................................................................................................................... 1

2 Références normatives ................................................................................................................................................................................... 1

3 Termes et définitions ....................................................................................................................................................................................... 1

4 Symboles et abréviations ............................................................................................................................................................................. 7

5 Type d’échantillon .............................................................................................................................................................................................. 8

6 Plage de mesure .................................................................................................................................................................................................... 8

7 Limite de détection ............................................................................................................................................................................................ 9

8 Principe .......................................................................................................................................................................................................................... 9

9 Réactifs ........................................................................................................................................................................................................................10

10 Appareillage ...........................................................................................................................................................................................................10

10.1 Prélèvement d’air ...............................................................................................................................................................................10

10.1.1 Cassette porte-filtre....................................................................................................................................................10

10.1.2 Pompe de prélèvement ............................................................................................................................................11

10.1.3 Support ..................................................................................................................................................................................11

10.1.4 Prélèvement individuel ...........................................................................................................................................11

10.1.5 Débitmètre .........................................................................................................................................................................11

10.2 Laboratoire de préparation des échantillons ............................................................................................................11

10.3 Équipement d’analyse ....................................................................................................................................................................12

10.3.1 Microscope électronique à transmission .................................................................................................12

10.3.2 Analyse en dispersion d’énergie des rayons X ....................................................................................14

10.3.3 Four à plasma...................................................................................................................................................................14

10.3.4 Évaporateur sous vide ..............................................................................................................................................14

10.3.5 Appareil à pulvérisation cathodique ...........................................................................................................14

10.3.6 Béchers ..................................................................................................................................................................................14

10.3.7 Source de vide .................................................................................................................................................................15

10.3.8 Appareil de filtration en verre ...........................................................................................................................15

10.3.9 Laveur à solvant (laveur Jaffe) ..........................................................................................................................15

10.3.10 Dissolveur à condensation ...................................................................................................................................16

10.3.11 Plaque chauffante ou étuve ..................................................................................................................................17

10.3.12 Bain à ultrasons .............................................................................................................................................................17

10.3.13 Réplique d’un réseau carbone ...........................................................................................................................17

10.3.14 Grilles d’échantillons d’étalonnage pour SDEX ..................................................................................17

10.3.15 Aiguiseur d’électrodes en carbone ................................................................................................................18

10.3.16 Micropipettes jetables ..............................................................................................................................................18

10.3.17 Thermomètre ...................................................................................................................................................................18

10.3.18 Chronomètre ....................................................................................................................................................................18

10.4 Consommables .....................................................................................................................................................................................18

10.4.1 Grilles de microscope électronique en cuivre ou en nickel ......................................................18

10.4.2 Grilles de microscope électronique en or ou en nickel ................................................................18

10.4.3 Feuille d’aluminium ........................................................................................................................................... .........18

10.4.4 Électrodes en carbone ..............................................................................................................................................19

10.4.5 Outils et fournitures courants pour microscopie électronique ............................................19

10.4.6 Échantillons d’amiante de référence ...........................................................................................................19

10.4.7 Échantillons de référence de fibres minérales autres que l’amiante ...............................19

11 Prélèvement d’échantillons d’air .....................................................................................................................................................19

11.1 Calcul de la sensibilité analytique .......................................................................................................................................19

11.2 Mode opératoire de prélèvement d’échantillons ......... ...........................................................................................20

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ISO 13794:2019(F)

12 Mode opératoire d’analyse ......................................................................................................................................................................21

12.1 Généralités ...............................................................................................................................................................................................21

12.2 Nettoyage des cassettes de prélèvement .......................................................................................................................21

12.3 Préparation des filtres analytiques ....................................................................................................................................22

12.3.1 Sélection de l’aire du filtre pour la calcination ...................................................................................22

12.3.2 Calcination de filtres de prélèvement d’échantillons ....................................................................22

12.3.3 Dispersion aqueuse des cendres résiduelles à partir des filtres de

prélèvement d’échantillons .................................................................................................................................22

12.3.4 Assemblage du système de filtration des dispersions aqueuses .........................................22

12.3.5 Filtration des dispersions aqueuses ............................................................................................................23

12.4 Préparation d’échantillons MET à partir de filtres analytiques en PC .................................................24

12.4.1 Sélection de l’aire du filtre pour le dépôt de carbone ...................................................................24

12.4.2 Dépôt de carbone sur des portions de filtre .........................................................................................24

12.4.3 Préparation du laveur Jaffe ..................................................................................................................................24

12.4.4 Mise en place des échantillons dans le laveur Jaffe.........................................................................24

12.5 Préparation d’échantillons MET à partir de filtres analytiques en ester de cellulose ............25

12.5.1 Sélection de l’aire du filtre à préparer ........................................................................................................25

12.5.2 Préparation de la solution de réduction des filtres en ester de cellulose ....................25

12.5.3 Mode opératoire de réduction du filtre .....................................................................................................25

12.5.4 Décapage plasma de la surface du filtre ...................................................................................................25

12.5.5 Dépôt de carbone .........................................................................................................................................................25

12.5.6 Préparation du laveur Jaffe ..................................................................................................................................25

12.5.7 Mise en place des échantillons dans le laveur Jaffe.........................................................................25

12.6 Critères d’acceptation des grilles d’échantillons MET .......................................................................................26

12.7 Mode opératoire de comptage des structures par MET ...................................................................................27

12.7.1 Généralités .........................................................................................................................................................................27

12.7.2 Mesurage de l’aire moyenne d’ouverture de grille ..........................................................................27

12.7.3 Modes opératoires d’alignement et d’étalonnage du MET .......................................................27

12.7.4 Détermination du critère d’arrêt de l’examen au MET ................................................................27

12.7.5 Mode opératoire général de comptage et d’analyse de dimensions des

structures ............................................................................................................................................................................28

12.7.6 Estimation de la concentration massique en fibres et en faisceaux d’amiante ......29

12.7.7 Exigences de grossissement ................................................................................................................................29

12.8 Déterminations des blancs et du contrôle qualité .................................................................................................31

12.9 Calcul des résultats ...........................................................................................................................................................................32

13 Caractéristiques de performance ....................................................................................................................................................32

13.1 Généralités ...............................................................................................................................................................................................32

13.2 Interférences et limites à l’identification des fibres ............................................................................................32

13.3 Fidélité et exactitude .......................................................................................................................................................................33

13.3.1 Fidélité ...................................................................................................................................................................................33

13.3.2 Exactitude ...........................................................................................................................................................................33

13.3.3 Analyses inter- et intralaboratoires .............................................................................................................34

13.4 Limite de détection ...........................................................................................................................................................................34

14 Rapport d’essai ....................................................................................................................................................................................................34

Annexe A (normative) Détermination des conditions de fonctionnement du four à plasma ................38

Annexe B (normative) Détermination et normalisation des conditions de fonctionnement

du bain à ultrasons ..........................................................................................................................................................................................39

Annexe C (normative) Modes opératoires d’étalonnage ..............................................................................................................41

Annexe D (normative) Critères de comptage des structures ...................................................................................................44

Annexe E (normative) Mode opératoire d’identification des fibres .................................................................................55

Annexe F (normative) Détermination de la concentration en fibres et faisceaux d’amiante

d’une longueur supérieure à 5 µm, et de la concentration en fibres d’amiante

équivalent MOCP ................................................................................................................................................................................................72

Annexe G (normative) Calcul des résultats .................................................................................................................................................73

iv © ISO 2019 – Tous droits réservés
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ISO 13794:2019(F)

Annexe H (normative) Mode opératoire d’essai pour déterminer l’adéquation de filtres de

prélèvement d’échantillons en ester de cellulose...........................................................................................................80

Annexe I (informative) Stratégies de prélèvement d’échantillons d’air .......................................................................81

Bibliographie ...........................................................................................................................................................................................................................82

© ISO 2019 – Tous droits réservés v
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ISO 13794:2019(F)
Avant-propos

L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes

nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est

en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude

a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,

gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.

L’ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui

concerne la normalisation électrotechnique.

Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont

décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier de prendre note des différents

critères d’approbation requis pour les différents types de documents ISO. Le présent document a été

rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www

.iso .org/directives).

L’attention est appelée sur le fait que certains des éléments du présent document peuvent faire l’objet de

droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable

de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant

les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de

l’élaboration du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de

brevets reçues par l’ISO (voir www .iso .org/brevets).

Les appellations commerciales éventuellement mentionnées dans le présent document sont données

pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un

engagement.

Pour une explication de la nature volontaire des normes, de la signification des termes et expressions

spécifiques de l’ISO liés à l’évaluation de la conformité, ou pour toute autre information au sujet de

l’adhésion de l’ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les

obstacles techniques au commerce (OTC), voir le lien suivant: www .iso .org/iso/fr/avant -propos .html.

Le présent document a été élaboré par le comité technique ISO/TC 146, Qualité de l’air, sous-comité SC 3,

Atmosphères ambiantes.

Cette deuxième édition annule et remplace la première édition (ISO 13794:1999), qui a fait l’objet d’une

révision technique. Les principales modifications par rapport à l’édition précédente sont les suivantes:

— l’utilisation de systèmes de visualisation électronique équipés d’un logiciel de mesure est autorisée;

— la densité de particules maximale pour les échantillons MET est augmentée de 10 % à 25 %;

— un mode opératoire simplifié d’identification des fibres de variétés d’amiante réglementées de

source connue et d’amiante richtérite/winchite, est autorisé;

— les exigences de consignation ont été modifiées pour pouvoir consigner les concentrations en fibres

et en faisceaux de plus de 5 µm et/ou les concentrations en fibres équivalent MOCP sans l’exigence

de consignation des concentrations en structures égales ou supérieures à 0,5 µm;

— l’exigence de consignation des intervalles de confiance à 95 % des concentrations en fibres a été

supprimée.

Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent

document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes

se trouve à l’adresse www .iso .org/fr/members .html.
vi © ISO 2019 – Tous droits réservés
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ISO 13794:2019(F)
Introduction

Le présent document est applicable au mesurage de l’amiante en suspension dans l’air ambiant pour

un nombre varié de situations, y compris les atmosphères intérieures des bâtiments, et à l’évaluation

précise de toute atmosphère. Les recherches médicales les plus avancées indiquant que la concentration

numérique des fibres ainsi que leur taille et leur type sont les meilleurs paramètres pour évaluer les

risques pour la santé liés à l’inhalation, une technique de comptage et de mesurage des fibres est la

seule qui soit valable. La plupart des fibres dans les atmosphères ambiantes ne sont pas de l’amiante,

et par conséquent il est nécessaire de les identifier. De nombreuses fibres d’amiante en suspension

dans l’air dans les atmosphères ambiantes ont des diamètres inférieurs à la limite de résolution du

microscope optique. Le présent document est fondé sur la microscopie électronique à transmission,

qui a une résolution adéquate pour permettre la détection de petites fibres et qui est actuellement

la seule technique capable d’identifier sans équivoque la majorité des fibres individuelles d’amiante.

Les fibres trouvées en suspension dans une atmosphère ambiante peuvent souvent être identifiées

sans équivoque, si un soin suffisant est apporté à l’analyse. Cependant, s’il faut identifier chaque fibre

ainsi, le coût de l’analyse devient prohibitif. En raison des insuffisances des instruments ou de la

nature des particules, certaines fibres ne peuvent pas être identifiées de façon positive comme étant

de l’amiante, même si les mesures indiquent toutes qu’elles pourraient en être. Des facteurs subjectifs

et instrumentaux interviennent dans ces mesures, et en conséquence une définition très précise de la

méthode d’identification et de numération des fibres d’amiante est nécessaire.

En plus des fibres simples et des faisceaux, on trouve souvent l’amiante dans les échantillons d’air

sous forme de structures agrégées très complexes qui peuvent aussi être ou non agrégées à d’autres

particules. Le nombre de fibres et de faisceaux d’amiante incorporés dans ces structures complexes

dépasse souvent le nombre de fibres et de faisceaux isolés observés, et bon nombre d’entre eux peuvent

être complètement masqués dans les préparations de microscope électronique à transmission (MET)

par transfert direct. La méthode définie dans le présent document comprend des modes opératoires de

préparation d’échantillons qui entraîne la concentration sélective des fibres d’amiante, et l’élimination

des matières organiques, solubles dans l’eau et solubles dans l’acide. Ces modes opératoires ont pour

effet de disperser la majorité des agglomérats complexes et agrégats de fibres en leurs composants,

fibres et faisceaux, ce qui permet de quantifier plus précisément l’amiante présente dans l’échantillon

d’air. Toutes les techniques possibles de préparation des échantillons entraînent des modifications des

caractéristiques des particules en suspension dans l’air. Le prélèvement même de particules à partir

d’une dispersion tridimensionnelle sur une surface filtrante bidimensionnelle peut être considéré

comme apportant des modifications aux caractéristiques des particules; en outre, pour la plupart

des échantillons, ces caractéristiques sont aussi modifiées par les modes opératoires de préparation

des échantillons. Bien que la présente méthode entraîne la dispersion des agglomérats et agrégats

complexes, elle réduit les autres effets exercés sur la granulométrie des fibres et faisceaux de fibres.

Le présent document exige l’utilisation d’un mode opératoire très détaillé et logique pour réduire les

aspects subjectifs du mesurage. La méthode d’enregistrement des données spécifiée dans le document

est destinée à permettre une réévaluation des données de comptage des fibres lorsque de nouvelles

données médicales seront disponibles.

Le présent document décrit la méthode d’analyse applicable à un seul filtre à air. Cependant, l’une

des plus grandes erreurs qui peuvent se produire lors de la caractérisation de l’amiante dans les

atmosphères ambiantes est associée à la variabilité entre des échantillons de filtre. Pour cette raison, il

est nécessaire de prévoir un plan d’échantillonnage stratifié afin de déterminer l’exactitude et la fidélité

de la norme.

La comparaison entre les résultats obtenus à l’aide de ce mode opératoire de transfert indirect et ceux

obtenus à l’aide du mode opératoire de transfert direct ne peut pas être effectuée a priori. Cela ne peut

être effectué qu’en réalisant une étude comparative spécifique du site, tenant compte de la taille des

fibres et du type d’amiante, ainsi que de la nature de la source de l’amiante en suspension dans l’air.

© ISO 2019 – Tous droits réservés vii
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NORME INTERNATIONALE ISO 13794:2019(F)
Air ambiant — Dosage des fibres d'amiante — Méthode
par microscopie électronique à transmission par transfert
indirect
1 Domaine d’application

Le présent document spécifie une méthode de référence utilisant la microscopie électronique à

transmission pour la détermination de la concentration en fibres et structures d’amiante en suspension

dans l’air dans les atmosphères ambiantes, notamment les atmosphères intérieures de bâtiments, et

pour l’évaluation détaillée des structures d’amiante dans les atmosphères. Le mode opératoire de

préparation des échantillons comprend la calcination et la dispersion des particules recueillies, de sorte

que la totalité de l’amiante est mesurée, y compris l’amiante initialement incorporée dans les agrégats

particulaires ou les particules de matériaux composites. Les longueurs, largeurs et rapports longueur/

largeur des fibres et faisceaux d’amiante sont mesurés. Ils permettent également, conjointement avec

la densité du type d’amiante, de calculer la concentration massique totale d’amiante en suspension

dans l’air. La méthode permet de déterminer le(s) type(s) de fibres d’amiante présentes. La méthode

ne peut pas faire la différence entre les fibres individuelles d’amiante amphibole et fragments allongés

(fragments de clivage et particules aciculaires) et les analogues non asbestiformes du même minéral

[12]
amphibole .
2 Références normatives

Les documents suivants sont cités dans le texte de sorte qu’ils constituent, pour tout ou partie de leur

contenu, des exigences du présent document. Pour les références datées, seule l’édition citée s’applique.

Pour les références non datées, la dernière édition du document de référence s'applique (y compris les

éventuels amendements).
ISO 4225, Qualité de l’air — Aspects généraux — Vocabulaire
3 Termes et définitions

Pour les besoins du présent document, les termes et définitions donnés dans l’ISO 4225 ainsi que les

suivants s’appliquent.
L’ISO et l’IEC tiennent à jour des bases de données terminologiques
...

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