ISO 22262-2

International
Standard
Second edition
Air quality — Bulk materials —
Part 2:
Quantitative determination of
asbestos by gravimetric and
microscopical methods
Qualité de l'air — Matériaux solides —
Partie 2: Dosage quantitatif de l'amiante en utilisant les
méthodes gravimétrique et microscopique
PROOF/ÉPREUVE
Reference number
© ISO 2025
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PROOF/ÉPREUVE
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 6
5 Determination of analytical requirements . 6
6 Range . 7
7 Limit of quantification . 7
8 Principle . 8
9 Safety precautions. 8
10 Apparatus . 8
11 Reagents . 10
12 Sample size and homogeneity . 10
12.1 Sample size .10
12.2 Representative sample .10
13 Methods for gravimetric matrix reduction .11
13.1 General .11
13.2 Data recording .11
13.3 Selection and pre-treatment of a representative sub-sample . 13
13.3.1 General . 13
13.3.2 Plasters without aggregate . 13
13.3.3 Plasters with aggregate . 13
13.3.4 Cements with and without aggregate . 13
13.3.5 Floor tiles . 13
13.3.6 Asphaltic materials without aggregate .14
13.3.7 Asphaltic materials with aggregate .14
13.3.8 Caulkings, mastics, putties, groutings and wall joint compounds .14
13.3.9 Cellulosic materials .14
13.3.10 Textured coatings .14
13.4 Removal of organic materials by ashing .14
13.4.1 General .14
13.4.2 Procedure . 15
13.5 Acid treatment and sedimentation procedures . 15
13.5.1 General . 15
13.5.2 Procedure for acid treatment of samples containing soluble constituents, with
or without insoluble aggregate . 15
13.5.3 Procedure for resilient floor tile .17
13.5.4 Examination of materials for amphibole fibres .17
14 Procedures for quantification of the mass fraction of asbestos in the final residue from
gravimetric matrix reduction . .18
14.1 General .18
14.2 Examination of the residue on the filter and selection of the appropriate procedure .19
14.2.1 General .19
14.2.2 Gravimetric measurements alone .19
14.2.3 Visual estimation by PLM, SEM or TEM observation .19
14.2.4 Point counting by PLM or SEM . 20
14.2.5 Determination of asbestos mass fraction from fibre measurements made by
SEM or TEM .24
PROOF/ÉPREUVE
iii
15 Determination of asbestos in talc and other mineral powders .26
15.1 General . 26
15.2 Separation of chrysotile and amphibole by heavy liquid centrifugation .27
15.3 Determination of chrysotile and amphibole in talc and other mineral powders by TEM .27
15.3.1 General .27
15.3.2 Specimen preparation .27
15.3.3 Determination of chrysotile and amphibole mass fraction . 28
15.3.4 Determination of chrysotile and amphibole numerical fibre concentrations . 28
15.4 Determination of the mass fraction of chrysotile and amphibole in talc and other
mineral powders by SEM . 28
16 Determination of asbestiform amphibole in vermiculite .28
16.1 General . 28
16.2 Required size of sample for analysis . 29
16.3 Sample pre-treatment . 29
16.3.1 Exfoliated vermiculite, loose fill vermiculite attic insulation and horticultural
vermiculite . 29
16.3.2 Vermiculite block fill insulation . 30
16.3.3 Vermiculite ore concentrate. 30
16.3.4 Vermiculite-containing horticultural products . 30
16.3.5 Sprayed vermiculite-containing fireproofing . 30
16.4 Separation of amphibole and measurement of the amphibole mass fraction .31
16.4.1 General .31
16.4.2 Manual separation of amphibole fibre bundles and weighing .31
16.4.3 Separation of amphibole by centrifugation in a heavy liquid .31
16.4.4 Confirmation of the absence of asbestos in the vermiculite sub-sample .32
17 Determination of compliance with legislative control limits .32
17.1 General .32
17.2 Gravimetry alone .32
17.3 Gravimetry combined with visual estimation . 33
17.4 Gravimetry combined with point counting . 33
17.5 Quantitative SEM or TEM fibre counting . 35
18 Method validation . .35
19 Test report .36
Annex A (normative) Types of commercial asbestos-containing materials and optimum
analytical procedures .37
Annex B (normative) Required centrifuge times for separation of amphibole in heavy liquid.44
Annex C (normative) Examples of test report .46
Bibliography .50
PROOF/ÉPREUVE
iv
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 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 22262-2:2014), which has been technically
revised.
The main changes are as follows:
— procedures for determination of asbestos mass fraction and numerical fibre concentration in talc and
other mineral powders have been added;
— an alternate procedure, following gravimetric matrix reduction, for determination of the asbestos mass
fraction on filters that exhibit only trace levels of fibres has been added.
A list of all parts in the ISO 22262 series can be found on the ISO website.
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.
PROOF/ÉPREUVE
v
Introduction
In the past, asbestos was used in a wide range of products. Materials containing high proportions of asbestos
were used in buildings and in industry for fireproofing, thermal insulation and acoustic insulation. Asbestos
was also used to reinforce materials, to improve fracture and bending characteristics. A large proportion of
the asbestos produced was used in asbestos-cement products. These include flat sheets, tiles and corrugated
sheets for roofing, pipes and open troughs for collecting rainwater, and pressure pipes for supplying potable
water. Asbestos was also incorporated into products such as decorative coatings and plasters, glues, sealants
and resins, floor tiles, gaskets and road paving. In some products asbestos was incorporated to modify
rheological properties, for example in the manufacture of ceiling tile panels and oil drilling muds.
Three varieties of asbestos found extensive commercial application. Chrysotile accounted for approximately
95 % of consumption, and therefore this is the variety that is encountered most frequently during analysis of
samples. Amosite and crocidolite accounted for almost all of the balance, with a very small contribution from
anthophyllite. Amosite was generally used as fireproofing or in thermal insulation products. Crocidolite was
also used as fireproofing and thermal insulation products, but because it is highly resistant to acids, it also
found application as a reinforcing fibre in acid containers such as those used for lead-acid batteries, and in
some gaskets. Materials containing commercial anthophyllite are relatively rare, but it also has been used
as a filler and reinforcing fibre in composite materials, and as a filtration medium. Tremolite asbestos and
actinolite asbestos were not extensively used commercially, but they sometimes occur as contamination
of other commercial minerals. Richterite asbestos and Winchite asbestos occur at mass fractions between
0,01 % and 6 % in vermiculite formerly mined at Libby, Montana, USA. Vermiculite from this source was
widely distributed and is often found as loose fill insulation and as a constituent in a range of construction
materials and fireproofing.
While the asbestos mass fraction in some products can be very high and in some cases approach 100 %,
in other products the mass fractions of asbestos used were significantly lower and often between 1 % and
15 %. In some ceiling tile panels, the mass fraction of asbestos used was close to 1 %. There are only a
few known materials in which the asbestos mass fraction used was less than 1 %. Some adhesives, sealing
compounds and fillers were manufactured in which asbestos mass fractions were lower than 1 %. There
are no known commercially manufactured materials in which any one of the common asbestos varieties
(chrysotile, amosite, crocidolite or anthophyllite) was intentionally added at mass fractions lower than 0,1 %.
ISO 22262-1 specifies procedures for collection of samples and qualitative analysis of commercial bulk
materials for the presence of asbestos. A visual estimate of the asbestos mass fraction can also be made.
While it is recognized that the accuracy and reproducibility of such estimates is very limited, for many of
the types of materials being analysed these estimates are sufficient to establish that the mass fraction of
asbestos in a manufactured product is, without doubt, well above any of the regulatory limits.
Given the wide range of matrix materials into which asbestos was incorporated, microscopy alone cannot
provide reliable analyses of all types of asbestos-containing materials in untreated samples. This document
extends the applicability and limit of detection of microscopical analysis by the use of simple procedures
such as ashing, acid treatment, sedimentation and heavy liquid density separation prior to microscopical
examination. These procedures should be used when the asbestos concentration has been estimated to be
very low, by using ISO 22262-1.
This document also specifies procedures for determination of the numerical concentration of mineral fibres
in mineral powders such as talc, wollastonite, sepiolite, attapulgite (palygorskite), calcite or dolomite, and
commercial products containing these minerals.
A prerequisite for use of this document and subsequent parts of the ISO 22262 series is that the sample
first be examined according to ISO 22262-1 by knowledgeable analysts who are familiar with the specified
[7][8][9][10]
analytical procedures.
PROOF/ÉPREUVE
vi
International Standard ISO 22262-2:2025(en)
Air quality — Bulk materials —
Part 2:
Quantitative determination of asbestos by gravimetric and
microscopical methods
1 Scope
This document specifies procedures for quantification of asbestos mass fractions below approximately 5 %,
and for quantitative determination of asbestos in vermiculite, other industrial minerals and commercial
products that incorporate these minerals.
This document is applicable to the quantitative analysis of:
a) any material for which the estimate of asbestos mass fraction obtained using ISO 22262-1 is deemed
to be of insufficient precision to reliably classify the regulatory status of the material (i.e. whether the
material is subject to asbestos regulations in the particular jurisdiction) or for which it is considered
necessary to obtain further evidence to demonstrate the absence of asbestos;
b) resilient floor tiles, asphaltic materials, roofing felts and any other materials in which asbestos is
embedded in an organic matrix;
c) wall and ceiling plasters, with or without aggregate;
d) vermiculite and commercial products containing vermiculite;
e) mineral powders such as talc, wollastonite, sepiolite, attapulgite (palygorskite), calcite or dolomite, and
commercial products containing these minerals.
This document primarily applies to samples in which asbestos has been identified at estimated mass
fractions lower than approximately 5 % by sample mass. This document is also applicable to samples that
can contain asbestos at low mass fractions incorporated into matrix material such that microscopical
examination of the untreated sample is either not possible or unreliable.
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 13794:2019, Ambient air — Determination of asbestos fibres — Indirect-transfer transmission electron
microscopy method
ISO 14887, Sample preparation — Dispersing procedures for powders in liquids
ISO 22262-1, Air quality — Bulk materials — Part 1: Sampling and qualitative determination of asbestos in
commercial bulk materials
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
PROOF/ÉPREUVE
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// 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 10312:2019, 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
A K, Na;
2+
B Fe , Mn, Mg, Ca, Na;
3+ 2+
C Al, Cr, Ti, Fe , Mg, Fe ;
3+
T 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 (3.12) in two directions parallel to the crystal faces and
intersecting at angles of about 56° and 124°.
[SOURCE: ISO 10312:2019, 3.2]
3.3
amphibole asbestos
amphibole (3.2) in an asbestiform (3.6)habit (3.22)
[SOURCE: ISO 10312:2019, 3.3]
3.4
analytical sensitivity
calculated structure concentration equivalent to counting of one structure in the analysis
Note 1 to entry: Analytical sensitivity is expressed in structures per gram.
Note 2 to entry: Analytical sensitivity is applicable to measurements carried out on mineral powders for which the
results are reported in terms of the numerical concentration of fibres (3.20) per gram.
3.5
anisotropic
state or quality of having different properties along different axes
EXAMPLE An anisotropic transparent particle can show different refractive indices with the vibration direction
of incident light.
PROOF/ÉPREUVE
3.6
asbestiform
specific type of mineral fibrosity in which the fibres (3.20) and fibrils (3.19) possess high tensile strength
and flexibility
[SOURCE: ISO 10312:2019, 3.5]
3.7
asbestos
group of silicate minerals belonging to the serpentine (3.32) and amphibole (3.2) groups which have
crystallized in the asbestiform (3.6)habit (3.22), causing them to be easily separated into long, thin, flexible,
strong fibres (3.20) when crushed or processed
Note 1 to entry: The Chemical Abstracts Service Registry Numbers of the most common asbestos varieties are:
chrysotile (3.11) (12001–29–5), crocidolite (12001–28–4), grunerite asbestos (amosite) (12172–73–5), anthophyllite
asbestos (77536–67–5), tremolite asbestos (77536–68–6) and actinolite asbestos (77536–66–4). Other varieties of
[11]
asbestiform amphibole, such as Richterite asbestos and Winchite asbestos , are also found in some products such as ®
vermiculite and talc. CAS Registry Number is a trademark of the American Chemical Society (ACS). This information
is given for the convenience of users of this document and does not constitute an endorsement by ISO of the product
named. Equivalent products may be used if they can be shown to lead to the same results.
[SOURCE: ISO 10312:2019, 3.6, modified — in Note 1 to entry, "may" has been changed to "can" in the second
sentence, and the third, four and fifth sentences have been added.]
3.8
asbestos point
point (3.27) that coincides with an asbestos (3.7)fibre (3.20)
3.9
aspect ratio
ratio of length to width of a particle
[SOURCE: ISO 10312:2019, 3.8]
3.10
birefringence
maximum difference between refractive indices due to double refraction
3.11
chrysotile
fibrous mineral of the serpentine (3.32) group which has the nominal composition:
Mg Si O (OH)
3 2 5 4
Note 1 to entry: Most natural chrysotile deviates little from this nominal composition. In some varieties of chrysotile,
3+ 3+ 2+ 3+ 2+ 2+ 2+
minor substitution of silicon by Al can occur. Minor substitution of magnesium by Al , Fe , Fe , Ni , Mn and Co
can also be present. Chrysotile is the most prevalent type of asbestos (3.7).
[SOURCE: ISO 10312:2019, 3.11, modified — "may" has been changed in two instances to "can" in Note 1 to entry.
3.12
cleavage
breaking of a mineral along one of its crystallographic directions
[SOURCE: ISO 10312:2019, 3.12]
3.13
cleavage fragment
fragment of a crystal that is bound by cleavage (3.12) faces
Note 1 to entry: Crushing of non-asbestiform amphibole (3.2) generally yields elongated fragments that conform to the
definition of a fibre (3.20).
PROOF/ÉPREUVE
[SOURCE: ISO 10312:2019, 3.13]
3.14
crossed polars
state in which the polarization directions of the polars (3.30) (polarizer and analyser) are mutually
perpendicular
[SOURCE: ISO 10934:2025, 3.1.124.2]
3.15
dispersion
variation of refractive index (3.31) with wavelength of light
[SOURCE: ISO 7348:1992, 05.03.26]
3.16
dispersion staining
effect produced when a transparent object is immersed in a surrounding medium, the refractive index (3.31)
of which is equal to that of the object at a wavelength in the visible range, but which has a significantly
higher optical dispersion (3.15) than the object
Note 1 to entry: Only the light refracted at the edges of the object is imaged, and this gives rise to colours at the
interface between the object and the surrounding medium. The particular colour is a measure of the wavelength at
which the refractive index of the object and that of the medium are equal.
3.17
empty point
point (3.27) that does not coincide with any particle or fibre (3.20)
3.18
energy dispersive X-ray analysis
EDXA
measurement of the energies and intensities of X-rays by use of a solid-state detector and multi-channel
analyser system
[SOURCE: ISO 10312:2019, 3.18]
3.19
fibril
single fibre (3.20) of asbestos (3.7) which cannot be further separated longitudinally into smaller components
without losing its fibrous properties or appearances
[SOURCE: ISO 10312:2019, 3.21]
3.20
fibre
elongated particle that has parallel or stepped sides
Note 1 to entry: For the purposes of this document, a fibre has an aspect ratio (3.9) equal to or greater than 3:1.
[SOURCE: ISO 10312:2019, 3.22]
3.21
fibre bundle
structure composed of parallel, smaller diameter fibres (3.20) attached along their lengths
Note 1 to entry: A fibre bundle can exhibit diverging fibres at one or both ends.
[SOURCE: ISO 10312:2019, 3.23, modified — "may" has been changed to "can" in Note 1 to entry.]
PROOF/ÉPREUVE
3.22
habit
characteristic crystal growth form, or combination of these forms, of a mineral, including characteristic
irregularities
[SOURCE: ISO 10312:2019, 3.25]
3.23
gravimetric matrix reduction
procedure in which constituents of a material are selectively dissolved or otherwise separated, leaving a
residue in which any asbestos (3.7) present in the original material is concentrated
3.24
isotropic
having the same properties in all directions
[SOURCE: ISO 14686:2003, 2.23]
3.25
matrix
material in a bulk sample within which fibres (3.20) are dispersed
3.26
non-empty point
point (3.27) that coincides with either a particle or an asbestos (3.7)fibre (3.20)
3.27
point
location on the sample where a record is made as to whether the location is occupied by a
particle or an asbestos (3.7)fibre (3.20), or whether the location is unoccupied
3.28
point counting
procedure in which random locations are examined on a sample to determine whether each location is
occupied by a particle or an asbestos (3.7)fibre (3.20), or is unoccupied, and each type of event is enumerated
3.29
polarized light
light in which the vibrations are partially or completely suppressed in certain directions at any given instant
Note 1 to entry: The vector of vibration may describe a linear, circular or elliptical shape.
[SOURCE: ISO 10934:2025, 3.1.93.1]
3.30
polar
device which selects plane-polarized light (3.29) from natural light
[SOURCE: ISO 10934:2025, 3.1.124]
3.31
refractive index
n
ratio of the speed of light (more exactly, the phase velocity) in a vacuum to that in a given medium
[SOURCE: ISO 10934:2025, 3.1.131]
PROOF/ÉPREUVE
3.32
serpentine
group of common rock-forming minerals having the nominal formula:
Mg Si O (OH)
3 2 5 4
[SOURCE: ISO 10312:2019, 3.35]
3.33
suspension
heterogeneous system in which a solid is distributed as fine particles in a liquid
[SOURCE: ISO 472:2013, 2.1135]
4 Abbreviated terms
EDXA energy dispersive X-ray analysis
MEC mixed esters of cellulose
PC polycarbonate
PLM polarized light microscopy
PTFE polytetrafluoroethylene
SEM scanning electron microscope
TEM transmission electron microscope
5 Determination of analytical requirements
Quantification of asbestos beyond the estimate of mass fraction achieved using ISO 22262-1 can be
unnecessary, depending on the applicable regulatory limit for definition of an asbestos-containing material,
the variety of asbestos identified, and whether the sample can be recognized as a manufactured product.
Common regulatory definitions of asbestos-containing materials range from “presence of any asbestos”,
to > 0,1 %, and > 0,5 % to > 1 % by mass fraction of one or more of the regulated asbestos varieties.
Following the use of ISO 22262-1 on many different samples, an analyst may determine the asbestos mass
fraction far exceeds these mass fraction regulatory limits. More precise quantification of asbestos in these
types of samples is unnecessary, since a more precise and significantly more expensive determination of
the asbestos mass fraction will neither change the regulatory status of the asbestos-containing material nor
any subsequent decisions concerning its treatment. Annex A shows a tabulation of most asbestos-containing
materials, the variety of asbestos used in these materials and the range of asbestos mass fraction that can be
present. Annex A also indicates whether, in general, the estimate of asbestos mass fraction provided by the
use of ISO 22262-1 is sufficient to establish the regulatory status of the material, or whether quantification
of asbestos by this document is necessary. Use Annex A for guidance on the probable asbestos mass fractions
in specific classes of product and to select the optimum analytical procedure to obtain a reliable result.
Asbestos was never deliberately incorporated for any functional purpose into commercially manufactured
asbestos-containing materials at mass fractions lower than 0,1 %. Accordingly, if any one or more of
the commercial asbestos varieties (chrysotile, amosite, crocidolite or anthophyllite) is detected in a
manufactured product, the assumption can be made that asbestos is present in the product at a mass
fraction exceeding 0,1 %. Therefore, if the regulatory definition of an asbestos-containing material in a
jurisdiction is either “presence of any asbestos” or greater than 0,1 %, then detection of one or more of the
commercial asbestos varieties in a recognizable manufactured product automatically defines the regulatory
status of the material. If the regulatory definition is either 0,5 % or 1 %, and the mass fraction of asbestos is
estimated to be lower than approximately 5 %, then more precise quantification is necessary to guarantee
the regulatory status of the material.
PROOF/ÉPREUVE
Detection of tremolite, actinolite, Richterite or Winchite in a material does not allow any assumptions to
be made regarding the asbestos mass fraction, because these asbestos varieties were, in general, not
deliberately added to products. Rather, they generally occur as accessory minerals in some of the constituents
used to manufacture products. Since the non-asbestiform analogues of the amphiboles are not generally
regulated, it is also necessary to discriminate between the asbestiform and non-asbestiform analogues of
these minerals. When present, these amphibole minerals often occur as mixtures of the two analogues in
industrial minerals.
In the case of talc and some other mineral powders, for some purposes it is necessary to quantify mineral
fibres in terms of the numerical concentration of fibres per gram of material, in addition to mass fraction.
It is not possible to specify a single analytical procedure for all types of material that can contain asbestos,
because the range of matrices in which the asbestos may be embedded is very diverse. Some materials are
amenable to gravimetric matrix reduction, while others are not.
The requirements for quantification of asbestos mass fraction beyond that achieved in ISO 22262-1 are
summarized in Table 1.
Table 1 — Summary of requirements for quantification of asbestos mass fraction in bulk samples
Regulatory control limit
Type of material
Mass Mass Mass
“Any asbestos”
fraction >0,1 % fraction >0,5 % fraction >1 %
If asbestos is detected at an estimated
C o m me r c i a l l y If any commercial asbestos variety is
mass fraction of <5 %, more precise
m a n u f a c t u r e d detected, no further quantification is
quantification is required to establish
product required.
the regulatory status of the material.
If any variety of
asbestos is de- If asbestos is detected at an estimated mass fraction of <5 %,
Other materials tected, no further more precise quantification is required to establish the
quantification is regulatory status of the material.
required.
6 Range
When this document is applied to a suitably prepared sample analysed by PLM, SEM or TEM, the target
range is from less than 0,001 % to 5 %. However, there is no upper limit to the concentration of asbestos
4 9
that can be determined. The target range for numerical fibre concentration is 10 to 10 fibres per gram. The
lower end of the range for both mass fraction and numerical fibre concentration depends on the proportion
of non-asbestos constituents that can be removed by gravimetric methods, the amount of the remaining
material that can be examined, and whether the analysis method is PLM, SEM or TEM.
7 Limit of quantification
The limit of quantification using this document is defined as the detection and identification of one fibre or
fibre bundle in the amount of sample examined. The limit of quantification that can be achieved depends on:
a) the nature of the matrix of the sample;
b) the size of the asbestos fibres and bundles;
c) the use of appropriate sample preparation and matrix reduction (gravimetric) procedures;
d) the amount of time expended on examination of the sample;
e) the method of analysis used, PLM, SEM or TEM.
PROOF/ÉPREUVE
With appropriate matrix reduction procedures that are selected based on the nature of the sample, the
limit of quantification can be lower than 0,001 % for mass fraction, and lower than 10 fibres per gram for
numerical fibre concentration.
8 Principle
A known mass of the material is heated in a furnace to a temperature of 450 °C ± 10 °C to remove organic
materials. Depending on the nature of the sample, the residue from the heating is treated with either
hydrochloric or sulphuric acid to dissolve acid-soluble constituents. If appropriate, water sedimentation is
then used to separate aggregate fragments and particles. For sensitive quantification of amphibole, some
materials can require a refluxing treatment in acid, followed by a reflux treatment in sodium hydroxide.
Alternatively, amphibole can be separated from many other constituents of lower densities by centrifugation
in a heavy liquid. The mass fraction of asbestos in the residue from these treatments is then determined by
appropriate PLM, SEM or TEM techniques. For fibres of specified dimensions within the capability of the
type of microscopy, numerical concentrations of fibres are determined by PLM, SEM or TEM fibre counting
on the analysed fraction of the sample.
9 Safety precautions
Handling asbestos is regulated by many jurisdictions, and regulations often specify a variety of procedures
to ensure that individuals performing work and those in close proximity are not exposed to excessive
concentrations of airborne asbestos fibres.
Care is necessary during sampling of materials that can contain asbestos, and precautions should be taken
to avoid creating and inhaling airborne asbestos particles when handling materials suspected of containing
asbestos. If the handling instructions in this clause are followed, it may be assumed that there is no
substantial release of fibres. In exceptional cases, more extensive precautions can be necessary to prevent
the release of airborne fibres.
Some of the procedures described use hazardous chemicals. These chemicals should be handled according
to safety requirements. Ashing of some materials also can result in discharge of toxic gases. Accordingly, the
muffl
...

ISO/PRF 22262-2
ISO/TC 146/SC 3 N455
ISO/TC 146/SC 3/WG 1
Secretariat: ANSI
Date: 2025-10-28
Air quality — Bulk materials —
Part 2:
Quantitative determination of asbestos by gravimetric and
microscopical methods
Second edition
Date: 2025-07-12
Qualité de l'air — Matériaux solides —
Partie 2: Dosage quantitatif de l'amiante en utilisant les méthodes gravimétrique et microscopique
PROOF
ISO/PRF 22262-2:2025(en)
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,
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iii
ISO/PRF 22262-2:2025(en)
Contents Page
Foreword . vi
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Abbreviated terms . 7
5 Determination of analytical requirements . 7
6 Range . 8
7 Limit of quantification . 9
8 Principle . 9
9 Safety precautions . 9
10 Apparatus . 9
11 Reagents . 11
12 Sample size and homogeneity . 11
12.1 Sample size . 11
12.2 Representative sample . 12
13 Methods for gravimetric matrix reduction . 12
13.1 General . 12
13.2 Data recording . 12
13.3 Selection and pre-treatment of a representative sub-sample . 15
13.4 Removal of organic materials by ashing . 16
13.5 Acid treatment and sedimentation procedures . 17
14 Procedures for quantification of the mass fraction of asbestos in the final residue from
gravimetric matrix reduction . 21
14.1 General . 21
14.2 Examination of the residue on the filter and selection of the appropriate procedure. 21
15 Determination of asbestos in talc and other mineral powders . 30
15.1 General . 30
15.2 Separation of chrysotile and amphibole by heavy liquid centrifugation . 30
15.3 Determination of chrysotile and amphibole in talc and other mineral powders by TEM . 31
15.4 Determination of the mass fraction of chrysotile and amphibole in talc and other mineral
powders by SEM . 32
16 Determination of asbestiform amphibole in vermiculite . 32
16.1 General . 32
16.2 Required size of sample for analysis . 33
16.3 Sample pre-treatment . 33
16.4 Separation of amphibole and measurement of the amphibole mass fraction . 35
17 Determination of compliance with legislative control limits . 36
17.1 General . 36
17.2 Gravimetry alone . 37
17.3 Gravimetry combined with visual estimation . 37
17.4 Gravimetry combined with point counting . 37
17.5 Quantitative SEM or TEM fibre counting . 41
iv
ISO/PRF 22262-2:2025(en)
18 Method validation . 41
19 Test report . 41
Annex A (normative) Types of commercial asbestos-containing materials and optimum
analytical procedures . 43
Annex B (normative) Required centrifuge times for separation of amphibole in heavy liquid . 51
Annex C (normative) Examples of test report . 54
Bibliography . 60

v
ISO/PRF 22262-2:2025(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 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 22262-2:2014), which has been technically
revised.
The main changes are as follows:
— — Addition of procedures for determination of asbestos mass fraction and numerical fibre concentration
in talc and other mineral powders have been added;
— — Addition of an alternate procedure, following gravimetric matrix reduction, for determination of the
asbestos mass fraction on filters that exhibit only trace levels of fibres has been added.
A list of all parts in the ISO 22262 series can be found on the ISO website.
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/PRF 22262-2:2025(en)
Introduction
In the past, asbestos was used in a wide range of products. Materials containing high proportions of asbestos
were used in buildings and in industry for fireproofing, thermal insulation and acoustic insulation. Asbestos
was also used to reinforce materials, to improve fracture and bending characteristics. A large proportion of
the asbestos produced was used in asbestos-cement products. These include flat sheets, tiles and corrugated
sheets for roofing, pipes and open troughs for collection ofcollecting rainwater, and pressure pipes for supply
ofsupplying potable water. Asbestos was also incorporated into products such as decorative coatings and
plasters, glues, sealants and resins, floor tiles, gaskets and road paving. In some products asbestos was
incorporated to modify rheological properties, for example in the manufacture of ceiling tile panels and oil
drilling muds.
Three varieties of asbestos found extensive commercial application. Chrysotile accounted for approximately
95 % of consumption, and therefore this is the variety that is encountered most frequently during analysis of
samples. Amosite and crocidolite accounted for almost all of the balance, with a very small contribution from
anthophyllite. Amosite was generally used as fireproofing or in thermal insulation products. Crocidolite was
also used as fireproofing and thermal insulation products, but because it is highly resistant to acids, it also
found application as a reinforcing fibre in acid containers such as those used for lead-acid batteries, and in
some gaskets. Materials containing commercial anthophyllite are relatively rare, but it also has been used as
a filler and reinforcing fibre in composite materials, and as a filtration medium. Tremolite asbestos and
actinolite asbestos were not extensively used commercially, but they sometimes occur as contamination of
other commercial minerals. Richterite asbestos and winchiteWinchite asbestos occur at mass fractions
between 0,01 % and 6 % in vermiculite formerly mined at Libby, Montana, USA. Vermiculite from this source
was widely distributed and is often found as loose fill insulation and as a constituent in a range of construction
materials and fireproofing.
While the asbestos mass fraction in some products can be very high and in some cases approach 100 %, in
other products the mass fractions of asbestos used were significantly lower and often between 1 % and 15 %.
In some ceiling tile panels, the mass fraction of asbestos used was close to 1 %. There are only a few known
materials in which the asbestos mass fraction used was less than 1 %. Some adhesives, sealing compounds
and fillers were manufactured in which asbestos mass fractions were lower than 1 %. There are no known
commercially manufactured materials in which any one of the common asbestos varieties (chrysotile, amosite,
crocidolite or anthophyllite) was intentionally added at mass fractions lower than 0,1 %.
ISO 22262--1 specifies procedures for collection of samples and qualitative analysis of commercial bulk
materials for the presence of asbestos. A visual estimate of the asbestos mass fraction maycan also be made.
While it is recognized that the accuracy and reproducibility of such estimates is very limited, for many of the
types of materials being analysed these estimates are sufficient to establish that the mass fraction of asbestos
in a manufactured product is, without doubt, well above any of the regulatory limits.
Because ofGiven the wide range of matrix materials into which asbestos was incorporated, microscopy alone
cannot provide reliable analyses of all types of asbestos-containing materials in untreated samples. This
document extends the applicability and limit of detection of microscopical analysis by the use of simple
procedures such as ashing, acid treatment, sedimentation and heavy liquid density separation prior to
microscopical examination. These procedures are recommendedshould be used when the asbestos
concentration has been estimated to be very low, by using Part ISO 22262-1 of this Standard.
This document also specifies procedures for determination of the numerical concentration of mineral fibres
in mineral powders such as talc, wollastonite, sepiolite, attapulgite (palygorskite), calcite or dolomite, and
commercial products containing these minerals.
A prerequisite for use of this document and subsequent parts of the ISO 22262 series is that the sample shall
have beenfirst be examined first byaccording to ISO 22262--1. ISO 22262 is for application by knowledgeable
[
analysts who are familiar with the specified analytical procedures. Error! Reference source not
vii
ISO/PRF 22262-2:2025(en)
][ ][ ][
found. Error! Reference source not found. Error! Reference source not found. Error! Reference
[1][2][3][4]
source not found. specified . It is not the intent of ISO 22262 to provide instruction in the fundamental
]
microscopical and analytical techniques.
viii
International Standard
Air quality — Bulk materials —
Part 2:
Quantitative determination of asbestos by gravimetric and
microscopical methods
1 Scope
This document specifies procedures for quantification of asbestos mass fractions below approximately 5 %,
and for quantitative determination of asbestos in vermiculite, other industrial minerals and commercial
products that incorporate these minerals.
This document is applicable to the quantitative analysis of:
a) a) any material for which the estimate of asbestos mass fraction obtained using ISO 22262--1 is
deemed to be of insufficient precision to reliably classify the regulatory status of the material, (i.e. whether
the material is subject to asbestos regulations in the particular jurisdiction) or for which it is considered
necessary to obtain further evidence to demonstrate the absence of asbestos;
b) b) resilient floor tiles, asphaltic materials, roofing felts and any other materials in which asbestos
is embedded in an organic matrix;
c) c) wall and ceiling plasters, with or without aggregate;
d) d) vermiculite, and commercial products containing vermiculite;
e) e) mineral powders such as talc, wollastonite, sepiolite, attapulgite (palygorskite), calcite or
dolomite, and commercial products containing these minerals.
This document is primarily intended for applicationapplies to samples in which asbestos has been identified
at estimated mass fractions lower than approximately 5 % by weight. Itsample mass. This document is also
applicable to samples that can contain asbestos at low mass fractions incorporated into matrix material such
that microscopical examination of the untreated sample is either not possible or unreliable.
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 22262-1, Air quality — Bulk materials — Part 1: Sampling and qualitative determination of asbestos in
commercial bulk materials
ISO 13794:2019, Ambient air — Determination of asbestos fibres — Indirect-transfer transmission electron
microscopy method
ISO 14887, Sample preparation — Dispersing procedures for powders in liquids
ISO/PRF 22262-2:2025(en)
ISO 22262-1, Air quality — Bulk materials — Part 1: Sampling and qualitative determination of asbestos in
commercial bulk materials
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
3.1 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 1379410312:2019, 3.1]
3.2 3.2
amphibole
group of rock-forming ferromagnesium silicate minerals, closely related in crystal form and composition, and
having the nominal formula: A0-1B2C5T8O22(OH,F,Cl)2, where
A B C T O (OH,F,Cl)
0-1 2 5 8 22 2
wh A = K, Na;
ere
2+
B = Fe , Mn, Mg, Ca, Na;
3+ 2+
C = Al, Cr, Ti, Fe , Mg, Fe ;
3+
T = Si, Al, Cr, Fe , Ti
[SOURCE: ISO 13794:2019, 3.2]
A K, Na;
2+
B Fe , Mn, Mg, Ca, Na;
3+ 2+
C Al, Cr, Ti, Fe , Mg, Fe ;
3+
T 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 (Error! Reference source not found.) in two directions parallel to
the crystal faces and intersecting at angles of about 56° and 124°.
[SOURCE: ISO 10312:2019, 3.32]
3.3
amphibole asbestos
amphibole (Error! Reference source not found.) in an asbestiform (Error! Reference source not
found.)habit (Error! Reference source not found.)
ISO/PRF 22262-2:2025(en)
[SOURCE: ISO 1379410312:2019, 3.3]
3.4 3.4
analytical sensitivity
calculated structure concentration in structures/gram, equivalent to counting of one structure in the analysis
[SOURCE: ISO 13794:2019, 3.5]
Note 1 to entry: this Analytical sensitivity is expressed in structures per gram.
Note 2 to entry: Analytical sensitivity is applicable to measurements carried out on mineral powders for which the results
are reported in terms of the numerical concentration of fibres (Error! Reference source not found.) per gram.
3.5
anisotropy
3.5
anisotropic
state or quality of having different properties along different axes
EXAMPLE An anisotropic transparent particle can show different refractive indices with the vibration direction of
incident light.
3.53.6 3.6
asbestiform
specific type of mineral fibrosity in which the fibres (Error! Reference source not found.) and fibrils (Error!
Reference source not found.) possess high tensile strength and flexibility
[SOURCE: ISO 1379410312:2019, 3.65]
3.63.7 3.7
asbestos
group of silicate minerals belonging to the serpentine (Error! Reference source not found.) and amphibole
(Error! Reference source not found.) groups which have crystallized in the asbestiform (Error! Reference
source not found.)habit (Error! Reference source not found.,), causing them to be easily separated into
long, thin, flexible, strong fibres (Error! Reference source not found.) when crushed or processed
[SOURCE: ISO 13794:2019, 3.7]
Note 1 to entry: The Chemical Abstracts Service Registry Numbers of the most common asbestos varieties are: chrysotile
(Error! Reference source not found.) (12001–29–5), crocidolite (12001–28–4), grunerite asbestos (amosite) (12172–
73–5), anthophyllite asbestos (77536–67–5), tremolite asbestos (77536–68–6) and actinolite asbestos (77536–66–4).
[
Other varieties of asbestiform amphibole, such as richteriteRichterite asbestos and winchiteWinchite asbestos Error!
[5]] ®
Reference source not found., , are also found in some products such as vermiculite and talc. CAS Registry Number is
a trademark of the American Chemical Society (ACS). This information is given for the convenience of users of this
document and does not constitute an endorsement by ISO of the product named. Equivalent products may be used if they
can be shown to lead to the same results.
3.8
[SOURCE: ISO 10312:2019, 3.6, modified — in Note 1 to entry, "may" has been changed to "can" in the second
sentence, and the third, four and fifth sentences have been added.]
3.8
asbestos point
point (Error! Reference source not found.) that coincides with an asbestos
(Error! Reference source not found.)fibre (Error! Reference source not found.in point counting)
ISO/PRF 22262-2:2025(en)
3.73.9 3.9
aspect ratio
ratio of length to width of a particle
[SOURCE: ISO 1379410312:2019, 3.108]
3.83.10 3.10
birefringence
maximum difference between refractive indices due to double refraction
3.93.11 3.11
chrysotile
fibrous mineral of the serpentine (Error! Reference source not found.) group which has the nominal
composition:
Mg3Si2O5(OH)4
[SOURCE: ISO 13794:2019, 3.13]
Note 1 to entry: Most natural chrysotile deviates little from this nominal composition. In some varieties of chrysotile,
3+ 3+ 2+ 3+ 2+ 2+
minor substitution of silicon by Al maycan occur. Minor substitution of magnesium by Al , Fe , Fe , Ni , Mn and
2+
Co maycan also be present. Chrysotile is the most prevalent type of asbestos (Error! Reference source not found.).
3.12
[SOURCE: ISO 10312:2019, 3.11, modified — "may" has been changed in two instances to "can" in Note 1 to
entry.
3.12
cleavage
breaking of a mineral along one of its crystallographic directions
[SOURCE: ISO 1379410312:2019, 3.1412]
3.103.13 3.13
cleavage fragment
fragment of a crystal that is boundedbound by cleavage (Error! Reference source not found.) faces
[SOURCE: ISO 13794:2019, 3.15]
Note 1 to entry: Crushing of non-asbestiform amphibole (Error! Reference source not found.) generally yields
elongated fragments that conform to the definition of a fibre (Error! Reference source not found.).
3.14
[SOURCE: ISO 10312:2019, 3.13]
3.14
crossed polars
state in which the polarization directions of the polars (Error! Reference source not found.) (polarizer and
analyser) are mutually perpendicular
[SOURCE: ISO 10934-:2025, 3.1:2002, .124.2.117.2]
3.113.15 3.15
dispersion
variation of refractive index (Error! Reference source not found.) with wavelength of light
ISO/PRF 22262-2:2025(en)
[SOURCE: ISO 7348:1992, 05.03.26]
3.123.16 3.16
dispersion staining
effect produced when a transparent object is immersed in a surrounding medium, the refractive index (Error!
Reference source not found.) of which is equal to that of the object at a wavelength in the visible range, but
which has a significantly higher optical dispersion (Error! Reference source not found.) than the object
Note 1 to entry: Only the light refracted at the edges of the object is imaged, and this gives rise to colours at the interface
between the object and the surrounding medium. The particular colour is a measure of the wavelength at which the
refractive index of the object and that of the medium are equal.
3.133.17 3.17
empty point
point (Error! Reference source not found.) that does not coincide with any
particle or fibre (Error! Reference source not found.in point counting)
3.143.18 3.18
energy dispersive X-ray analysis
EDXA
measurement of the energies and intensities of X-rays by use of a solid-state detector and multi-channel
analyser system
[SOURCE: ISO 1379410312:2019, 3.2218]
3.153.19 3.19
fibril
single fibre (Error! Reference source not found.) of asbestos (Error! Reference source not found.) which
cannot be further separated longitudinally into smaller components without losing its fibrous properties or
appearances
[SOURCE: ISO 1379410312:2019, 3.2521]
3.163.20 3.20
fibre
elongated particle whichthat has parallel or stepped sides
[SOURCE: ISO 13794:2019, 3.26]
Note 1 to entry: For the purposes of this document, a fibre is defined to havehas an aspect ratio (Error! Reference
source not found.) equal to or greater than 3:1.
3.21
[SOURCE: ISO 10312:2019, 3.22]
3.21
fibre bundle
structure composed of parallel, smaller diameter fibres (Error! Reference source not found.) attached along
their lengths
[SOURCE: ISO 13794:2019, 3.27]
Note 1 to entry: A fibre bundle maycan exhibit diverging fibres at one or both ends.
3.22[SOURCE: ISO 10312:2019, 3.23, modified — "may" has been changed to "can" in Note 1 to entry.]
ISO/PRF 22262-2:2025(en)
3.173.22
habit
characteristic crystal growth form, or combination of these forms, of a mineral, including characteristic
irregularities
[SOURCE: ISO 1379410312:2019, 3.3025]
3.183.23 3.23
gravimetric matrix reduction
procedure in which constituents of a material are selectively dissolved or otherwise separated, leaving a
residue in which any asbestos (Error! Reference source not found.) present in the original material is
concentrated
3.193.24 3.24
isotropic
having the same properties in all directions
[SOURCE: ISO 14686:2003, 2.23]
3.203.25 3.25
matrix
material in a bulk sample within which fibres (Error! Reference source not found.) are dispersed
3.213.26 3.26
non-empty point
where a point (Error! Reference source not found.) that coincides with either a particle or
an asbestos (Error! Reference source not found.)fibre (Error! Reference source not found.in point
counting)
3.223.27 3.27
point
in location on the sample where a record is made as to whether the location is occupied by
a particle or an asbestos (Error! Reference source not found.)fibre (Error! Reference source not found.,),
or whether the location is unoccupied
3.233.28 3.28
point counting
procedure in which random locations are examined on a sample to determine whether each location is
occupied by a particle or an asbestos (Error! Reference source not found.)fibre (Error! Reference source
not found.,), or is unoccupied, and each type of event is enumerated
3.243.29 3.29
polarized light
light in which the vibrations are partially or completely suppressed in certain directions at any given instant
[SOURCE: ISO 10934-1:2002, 2.88.1]
Note 1 to entry: The vector of vibration may describe a linear, circular or elliptical shape.
3.30
polarizer
polar placed in the light path before the object
[SOURCE: ISO 10934-:2025, 3.1:2002, 2.117.4.93.1]
ISO/PRF 22262-2:2025(en)
3.253.30 3.31
polar
device which selects plane-polarized light (Error! Reference source not found.) from natural light
[SOURCE: ISO 10934-:2025, 3.1:2002, 2.117.124]
3.263.31 3.32
refractive index
n
ratio of the speed of light (more exactly, the phase velocity) in a vacuum to that in a given medium
[SOURCE: ISO 10934-1:2002, 2.124:2025, 3.1.131]
3.273.32 3.33
serpentine
group of common rock-forming minerals having the nominal formula:
Mg3Si2O5(OH)4
[SOURCE: ISO 1379410312:2019, 3.4035]
3.283.33 3.34
suspension
heterogeneous system in which a solid is distributed as fine particles in a liquid
[SOURCE: ISO 472:2013, 2.1135]
4 Abbreviated terms
ED electron diffraction
EDXA energy dispersive X-ray analysis
MEC mixed esters of cellulose
PC polycarbonate
PLM polarized light microscopy
PTFE polytetrafluoroethylene
RI refractive index
SAED selected area electron diffraction
SEM scanning electron microscope
TEM transmission electron microscope
5 Determination of analytical requirements
Quantification of asbestos beyond the estimate of mass fraction achieved using ISO 22262--1 may notcan be
necessaryunnecessary, depending on the applicable regulatory limit for definition of an asbestos-containing
material, the variety of asbestos identified, and whether the sample can be recognized as a manufactured
product. Common regulatory definitions of asbestos-containing materials range from “presence of any
asbestos”, throughto > 0,1 %, and > 0,5 % to > 1 % by mass fraction of one or more of the regulated asbestos
varieties. Following the use of ISO 22262-1 on many different samples, an analyst may determine the asbestos
mass fraction far exceeds these mass fraction regulatory limits. More precise quantification of asbestos in
ISO/PRF 22262-2:2025(en)
these types of samples is unnecessary, since a more precise and significantly more expensive determination
of the asbestos mass fraction will neither change the regulatory status of the asbestos-containing material nor
any subsequent decisions concerning its treatment. Annex AAnnex A shows a tabulation of most asbestos-
containing materials, the variety of asbestos used in these materials, and the range of asbestos mass fraction
that can be present. Annex AAnnex A also indicates whether, in general, the estimate of asbestos mass fraction
provided by the use of ISO 22262--1 is sufficient to establish the regulatory status of the material, or whether
quantification of asbestos by this document is necessary. Use Annex AAnnex A for guidance on the probable
asbestos mass fractions in specific classes of product, and to select the optimum analytical procedure to obtain
a reliable result.
Asbestos was never deliberately incorporated for any functional purpose into commercially manufactured
asbestos-containing materials at mass fractions lower than 0,1 %. Accordingly, if any one or more of the
commercial asbestos varieties (chrysotile, amosite, crocidolite or anthophyllite) is detected in a manufactured
product, the assumption can be made that asbestos is present in the product at a mass fraction exceeding
0,1 %. Therefore, if the regulatory definition of an asbestos-containing material in a jurisdiction is either
“presence of any asbestos” or greater than 0,1 %, then detection of one or more of the commercial asbestos
varieties in a recognizable manufactured product automatically defines the regulatory status of the material.
If the regulatory definition is either 0,5 % or 1 %, and the mass fraction of asbestos is estimated to be lower
than approximately 5 %, then more precise quantification is necessary to guarantee the regulatory status of
the material.
Detection of tremolite, actinolite, Richterite or richterite/winchiteWinchite in a material does not allow any
assumptions to be made regarding the asbestos mass fraction, because these asbestos varieties were, in
general, not deliberately added to products. Rather, they generally occur as accessory minerals in some of the
constituents used to manufacture products. Since the non-asbestiform analogues of the amphiboles are not
generally regulated, it is also necessary to discriminate between the asbestiform and non-asbestiform
analogues of these minerals. When present, these amphibole minerals often occur as mixtures of the two
analogues in industrial minerals.
In the case of talc and some other mineral powders, for some purposes it is necessary to quantify mineral
fibres in terms of the numerical concentration of fibres per gram of material, in addition to mass fraction.
It is not possible to specify a single analytical procedure for all types of material that can contain asbestos,
because the range of matrices in which the asbestos may be embedded is very diverse. Some materials are
amenable to gravimetric matrix reduction, and somewhile others are not.
The requirements for quantification of asbestos mass fraction beyond that achieved in ISO 22262--1 are
summarized in 0Table 1.
Table 1 — Summary of requirements for quantification of asbestos mass fraction in bulk samples
Regulatory control limit
Mass Mass Mass
Type of material
“Any asbestos” fraction fraction fraction
> >0,1 % > >0,5 % > >1 %
If asbestos is detected at an estimated
Commercially If any commercial asbestos variety is
mass fraction of <5 %, more precise
manufactured detected, no further quantification is
quantification is required to establish
product required.
the regulatory status of the material.
If any variety of
If asbestos is detected at an estimated mass fraction of <5 %,
asbestos is
Other materials more precise quantification is required to establish the
detected, no
regulatory status of the material.
further
ISO/PRF 22262-2:2025(en)
Regulatory control limit
Mass Mass Mass
Type of material
“Any asbestos” fraction fraction fraction
> >0,1 % > >0,5 % > >1 %
quantification is
required.
6 Range
When this document is applied to a suitably prepared sample analysed by PLM, SEM or TEM, the target range
is from less than 0,001 % to 5 %. However, there is no upper limit to the concentration of asbestos that can be
4 9
determined. The target range for numerical fiberfibre concentration is 10 to 10 fibers/fibres per gram. The
lower end of the range for both mass fraction and numerical fibre concentration depends on the proportion
of non-asbestos constituents that can be removed by gravimetric methods, the amount of the remaining
material that can be examined, and whether the analysis method is PLM, SEM or TEM.
7 Limit of quantification
The limit of quantification using this document is defined as the detection and identification of one fibre or
fibre bundle in the amount of sample examined. The limit of quantification that can be achieved depends on:
a) a) the nature of the matrix of the sample;
b) b) the size of the asbestos fibres and bundles;
c) c) the use of appropriate sample preparation and matrix reduction (gravimetric) procedures;
d) d) the amount of time expended on examination of the sample; and,
e) e) the method of analysis used, PLM, SEM or TEM.
With appropriate matrix reduction procedures that are selected based on the nature of the sample, the limit
of quantification can be lower than 0,001 % for mass fraction, and lower than 10 fibres per gram for
numerical fibre concentration.
8 Principle
A known weightmass of the material is heated in a furnace to a temperature of 450 °C ± 10 °C to remove
organic materials. Depending on the nature of the sample, the residue from the heating is treated with either
hydrochloric or sulphuric acid to dissolve acid-soluble constituents. If appropriate, water sedimentation is
then used to separate aggregate fragments and particles. For sensitive quantification of amphibole, some
materials maycan require a refluxing treatment in acid, followed by a reflux treatment in sodium hydroxide.
Alternatively, amphibole can be separated from many other constituents of lower densities by centrifugation
in a heavy liquid. The mass fraction of asbestos in the residue from these treatments is then determined by
appropriate PLM, SEM or TEM techniques. For fibres of specified dimensions within the capability of the type
of microscopy, numerical concentrations of fibres are determined by PLM, SEM or TEM fibre counting on the
analysed fraction of the sample.
9 Safety precautions
Handling asbestos is regulated by many jurisdictions, and regulations often specify a variety of procedures to
ensure that individuals performing work and those in close proximity are not exposed to excessive
concentrations of airborne asbestos fibres.
ISO/PRF 22262-2:2025(en)
Care is necessary during sampling of materials that can contain asbestos, and precautions should be taken to
avoid creating and inhaling airborne asbestos particles when handling materials suspected of containing
asbestos. If the handling instructions in this clause are followed, it may be assumed that there is no substantial
release of fibres. In exceptional cases, more extensive precautions maycan be necessary to prevent the release
of airborne fibres.
Some of the procedures described use hazardous chemicals. These chemicals should be handled in accordance
with according to safety requirements. Ashing of some materials also can result in discharge of toxic gases.
Accordingly, the muffle furnace should be appropriately vented.
10 Apparatus
10.1 10.1 Dust extract hood. Handling and manipulation of bulk materials suspected to contain
asbestos shall be performed in a suitable dust extract hood, so that neither the analyst nor the laboratory
environment is exposed to airborne asbestos fibres. Discharge of air from the dust extract hood shall be
through a HEPA filter with a filtration efficiency that is equal to or exceeds 99,97 % for spherical particles of
0,3 µm diameter.
10.2 10.2 Sample comminution equipment. An agate mortar and pestle, or a mill, is requiredshall
be used for grinding of samples to suitable sizes for PLM examination.
10.3 10.3 Analytical balance, with a readability of 0,000 1 g or lower is requiredshall be used.
10.4 10.4 Muffle furnace, for ashing of samples to remove interfering organic constituents, a muffle
furnace with a minimum temperature range up to 800 °C, with a temperature stability of ±10 °C is
requiredshall be used.
10.5 10.5 Slide warmer, for drying of samples and preparation of microscope slides. Alternatively, an
oven may be used.
10.6 10.6 Glass filtration assembly (47 mm diameter), with 250 ml reservoir and glass frit base,
with side-arm vacuum filtration flask.
10.7 10.7 Glass filtration assembly (25 mm diameter), with 15 ml reservoir and glass frit base,
with side-arm vacuum filtration flask.
10.8 10.8 Side-arm vacuum flask, 1 000 ml volume.
10.9 10.9 Water aspirator, or other vacuum source for filtrations.
10.10 10.10 Magnetic stirrer, for removal of acid-soluble interfering constituents, a magnetic stirrer
with a glass or plastic-coated magnetic stir bar.
10.11 10.11 Glass reflux condenser system. A borosilicate glass reflux system, consisting of a 250 ml
round-bottomed flask with a vertical, water-cooled borosilicate glass condenser and a mantle heater is
requiredshall be used for the treatment of samples by the sequential refluxing in acid and alkali
procedureprocedures.
10.12 10.12 Centrifuge. A bench-top centrifuge is requiredshall be used for the separation of insoluble
residues during procedures including sequential refluxing in acid and alkali, or for separation of amphiboles
by centrifugation in a heavy liquid.
10.13 10.13 Glass centrifuge tubes, 15 ml volume.
ISO/PRF 22262-2:2025(en)
1) 3 3
10.14 10.14 Sink-Float or density bottle. Sink-Float Standard, , density 2 750 kg/m ± 5 kg/m
3 3
(2,75 g/cm ± 0,005 g/cm ) at 23 °C, for measurement of heavy liquid density. Alternatively, a 10 ml density
bottle may be used.
10.15 10.15 Equipment for microscopical analysis. Appropriate microscopy equipment as specified
in ISO 22262--1, for analysis of residues from the gravimetric reduction procedures.
10.16 10.16 Supplies for microscopical analysis in accordance with ISO 22262--1.
10.17 10.17 General laboratory supplies. The following supplies and equipment, or equivalent, are
requiredshall be used.
10.17.1 10.17.1 Glassine paper sheets, approximately 15 cm × 15 cm, for examination of
samples.
10.17.2 10.17.2 Scalpel holder and replacement disposable scalpel blades.
10.17.3 10.17.3 Sampling utensils, including tweezers, needles and spatulas.
10.17.4 10.17.4 Erlenmeyer flasks, 250 ml.
10.17.5 10.17.5 Crucibles, silica or glazed porcelain, with lids.
10.17.6 10.17.6 Petri dishes.
10.17.7 10.17.7 Pipettes and disposable pipette tips, 0 μl -to 1 000 μl and 0 μl -to 10 μl,
respectivey.
10.17.8 10.17.8 Disposable pipettes.
10.17.9 10.17.9 Disposable plastic beakers, 50 ml and 1 000 ml.
10.17.10 10.17.10 Borosilicate glass rods, 5 mm diameter, approximately 20 cm in length.
10.17.11 10.17.11 Polycarbonate filters, 0,4 μm pore size, 47 mm and 25 mm diameter, 0,2 µm
pore size, 25 mm diameter.
10.17.12 10.17.12 Gold-coated polycarbonate filters, 0,8 µm pore size, 25 mm diameter.
10.17.13 10.17.13 MEC filters, 0,45 µm porosity, 47 mm and 25 mm diameter, 5.,0 µm porosity,
25 mm diameter.
11 Reagents
11.1 11.1 Distilled or de-ionized water, filtered through a maximum 0,22 μm porosity MEC filter.
11.2 11.2 Concentrated hydrochloric acid, reagent grade.
11.3 11.3 Concentrated sulphuric acid, reagent grade.
11.4 11.4 Glacial acetic acid, reagent grade.
11.5 11.5 Sodium hydroxide, pellets, reagent grade.

1)
Sink-Float Standard is the trade name of a product supplied by Cargille Laboratories. This information is given for the
convenience of users of this document and does not constitute an endorsement by ISO of the product named. Equivalent
products may be used if they can be shown to
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