ISO/TS 21361:2025

Technical
Specification
ISO/TS 21361
Second edition
Nanotechnologies — Method to
2025-03
quantify air concentrations of
carbon black and amorphous silica
in the nanoparticle size range
in a mixed dust manufacturing
environment
Nanotechnologies — Méthode de quantification des
concentrations dans l'air de noir de carbone et de silice amorphe
à l'échelle nanométrique dans un environnement de fabrication
industrielle contenant des mélanges de poussières
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviations . 2
5 Principle . 2
6 Reagents . 3
7 Apparatus . 4
7.1 Air sampling — Equipment and consumable supplies.4
7.1.1 Electrical low cascade pressure impactor (ELPCI) .4
7.1.2 Limit of detection (LOD) .4
7.1.3 Real-time aerosol monitor .5
7.1.4 Vacuum pump .5
7.1.5 Polycarbonate substrate .5
7.1.6 Hydrocarbon grease .6
7.2 Analytical/microscopy laboratories .6
7.3 Sample analysis — Equipment and consumables .6
7.3.1 Transmission electron microscope (TEM).6
7.3.2 Energy dispersive spectrometry (EDS) .6
7.3.3 TEM grid .6
8 Air sample collection . 6
8.1 Sampling procedure .6
8.2 Determination of sampling time .6
8.3 Sample collection procedure.7
9 Procedure for analysis. 7
9.1 General .7
9.2 Preparation of substrates .7
9.3 Sample analysis . .8
9.3.1 Instrument conditions.8
9.3.2 Data collection .8
9.4 Calculation of air concentration .9
10 Uncertainties and performance criteria . 10
10.1 General .10
10.2 Particle counting with the electrical low pressure cascade impactor (ELPCI) .10
10.3 Particle analysis with transmission electron microscopy (TEM) and energy dispersive
spectrometry (EDS) .11
11 Test report .11
Annex A (informative) Case study overview .12
Bibliography .13

iii
Foreword
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of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
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This document was prepared by Technical Committee ISO/TC 229, Nanotechnologies.
This second edition cancels and replaces the first edition (ISO/TS 21361:2019) which has been technically
revised.
The main changes are as follows:
— references have been updated;
— minor clarifications have been made to the text.
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.

iv
Introduction
Nanomaterials are widely used in industrial settings in the manufacture of consumer products. Carbon
black and amorphous silica are commonly used in consumer products, such as rubber products, insulating
materials, and others. Although these materials typically exist as agglomerates in dimensions larger than
the nanoscale, there is also the potential for worker exposure to these materials in the nanoscale size
range. In spite of the widespread use of nanomaterials such as these, quantification of air concentrations of
specific nanomaterials in mixed dust settings, such as a manufacturing environment, has been challenging
to date and has been identified as a hindrance to the development of nano-specific occupational exposure
limits (see References [3], [4] and [6]). This method outlines a technique whereby particles of carbon black
and amorphous silica can be identified, distinguished, and quantified (in terms of air concentrations) by
size in such manufacturing settings. It is anticipated that although this method is specific to carbon black
and amorphous silica, the general principles of the method can be applied to many materials in a variety
of manufacturing environments. This method advances beyond existing techniques for analysis in that it
provides quantitative information regarding exposure to specific materials by size; many other methods
provide quantitative information on nanoparticle exposures that are incapable of differentiating by material
type. This method includes both a defined methodology for collecting air samples in the manufacturing
settings as well as a methodology for analysing the sample to obtain appropriate information for quantifying
air concentration of the materials of interest. Application of this methodology has recently been published in
the peer-reviewed literature (see Reference [5]).
This document specifies a method to quantify and identify particles of either carbon black or amorphous
silica, or both, in air samples collected in a mixed dust, industrial, manufacturing environment. It describes
air sample collection and the characterization of the particles in the air samples by both particle size and
elemental composition. The method is defined for air samples collected with an electrical low pressure
cascade impactor (ELPCI). However, the method is suitable for sampling in manufacturing environments
where there are a variety of particle types contributing to the overall atmosphere. The particles in the
air sample are collected in the various stages of a cascade impactor with cut-offs for median particle size
between 6 nm and 10 µm. This impactor determines the number particle size distributio
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