CEN ISO/TS 21083-2:2019

Test method to measure the efficiency of air filtration media against spherical nanomaterials - Part 2: Size range from 3 nm to 30 nm (ISO/TS 21083-2:2019)

This document specifies the testing instruments and procedure for determining the filtration efficiencies of flat sheet filter media against airborne nanoparticles in the range of 3 nm to 30 nm. The testing methods in this document are limited to spherical or nearly-spherical particles to avoid uncertainties due to the particle shape.

Prüfverfahren zur Messung der Effizienz von Luftfiltrationsmedien gegen sphärische Nanomaterialien - Teil 2: Partikelgrößenbereich von 3 bis 30 nm (ISO/TS 21083-2:2019)

Dieses Dokument legt die Prüfinstrumente und Prüfverfahren für die Bestimmung des Filtrationswirkungsgrads von planen Filtermedien gegen Nanoschwebstoffpartikel im Größenbereich zwischen 3 nm und 30 nm fest. Die Prüfverfahren in diesem Dokument sind auf kugelförmige oder fast kugelförmige Partikel beschränkt, um Unsicherheiten aufgrund der Partikelform zu vermeiden.

Méthode d'essai pour mesurer l'efficacité des médias de filtration d'air par rapport aux nanomatériaux sphériques - Partie 2: Spectre granulométrique de 3 nm à 30 nm (ISO/TS 21083-2:2019)

Le présent document spécifie les instruments et modes opératoires d'essai pour la détermination de l'efficacité de filtration d'un média filtrant plan par rapport à des nanoparticules en suspension dans l'air dans la plage de 3 nm à 30 nm. Les méthodes d'essai décrites dans le présent document sont limitées à des particules sphériques ou quasi-sphériques afin d'éviter les incertitudes liées à la forme des particules.

Preskusna metoda za merjenje učinkovitosti sredstev za filtriranje zraka, ki vsebuje kroglaste nanomateriale - 2. del: Velikost delcev od 3 nm do 30 nm (ISO/TS 21083-2:2019)

Ta dokument določa preskusne instrumente in postopek za učinkovitost filtracije ploščatih filtrirnih medijev za filtriranje zraka, ki vsebuje kroglaste nanomateriale v obsegu 3–30 nm.

General Information

• Status: Published
• Publication Date: 02-Apr-2019
• ICS: 91.140.30 - Ventilation and air-conditioning systems
• Technical Committee: CEN/TC 195 - Air filters for general air cleaning
• Drafting Committee: CEN/TC 195/WG 6 - Execution of Mandate M/461
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 03-Apr-2019
• Due Date: 09-Nov-2017
• Completion Date: 03-Apr-2019
• Mandate: M/461 - Mandate addressed to CEN, CENELEC and ETSI for Standardization activities regarding Nanotechnologies and Nanomaterials
• Ref Project: SIST-TS CEN ISO/TS 21083-2:2019 - Test method to measure the efficiency of air filtration media against spherical nanomaterials - Part 2: Particle size range from 3 nm to 30 nm (ISO/TS 21083-2:2019)

Standards Content (Sample)

SLOVENSKI STANDARD
01-junij-2019
3UHVNXVQDPHWRGD]DPHUMHQMHXþLQNRYLWRVWLVUHGVWHY]DILOWULUDQMH]UDNDNL
YVHEXMHNURJODVWHQDQRPDWHULDOHGHO9HOLNRVWGHOFHYRGQPGRQP
,6276
Test method to measure the efficiency of air filtration media against spherical
nanomaterials - Part 2: Particle size range from 3 nm to 30 nm (ISO/TS 21083-2:2019)
Méthode d'essai pour mesurer l'efficacité des médias de filtration d'air par rapport aux
nanomatériaux sphériques - Partie 2: Spectre granulométrique de 3 nm à 30 nm (ISO/TS
21083-2:2019)
Ta slovenski standard je istoveten z: CEN ISO/TS 21083-2:2019
ICS:
91.140.30 3UH]UDþHYDOQLLQNOLPDWVNL Ventilation and air-
VLVWHPL conditioning systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN ISO/TS 21083-2
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
April 2019
TECHNISCHE SPEZIFIKATION
ICS 91.140.30
English Version
Test method to measure the efficiency of air filtration
media against spherical nanomaterials - Part 2: Size range
from 3 nm to 30 nm (ISO/TS 21083-2:2019)
Méthode d'essai pour mesurer l'efficacité des médias
de filtration d'air par rapport aux nanomatériaux
sphériques - Partie 2: Spectre granulométrique de 3
nm à 30 nm (ISO/TS 21083-2:2019)
This Technical Specification (CEN/TS) was approved by CEN on 1 April 2019 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN ISO/TS 21083-2:2019 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (CEN ISO/TS 21083-2:2019) has been prepared by Technical Committee ISO/TC 142
"Cleaning equipment for air and other gases" in collaboration with Technical Committee CEN/TC 195
“Air filters for general air cleaning” the secretariat of which is held by UNI.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO/TS 21083-2:2019 has been approved by CEN as CEN ISO/TS 21083-2:2019 without any
modification.
TECHNICAL ISO/TS
SPECIFICATION 21083-2
First edition
2019-03
Test method to measure the efficiency
of air filtration media against
spherical nanomaterials —
Part 2:
Size range from 3 nm to 30 nm
Méthode d'essai pour mesurer l'efficacité des médias de filtration
d'air par rapport aux nanomatériaux sphériques —
Partie 2: Spectre granulométrique de 3 nm à 30 nm
Reference number
ISO/TS 21083-2:2019(E)
©
ISO 2019
ISO/TS 21083-2:2019(E)
© 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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

ISO/TS 21083-2:2019(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Symbols and abbreviated terms. 2
3.2.1 Symbols . 2
3.2.2 Abbreviated terms . 3
4 Principle . 3
5 Test materials . 4
5.1 General . 4
5.2 Solid phase aerosol — Silver test aerosol as an example . 4
5.3 Solid phase aerosol generation method . 4
6 Test setup . 5
6.1 General . 5
6.2 Specifications of setup . 7
6.2.1 Aerosol generation system . 7
6.2.2 Tubing . 7
6.2.3 DEMC . 7
6.2.4 Equilibrium charge distribution and neutralization of aerosol particles . 9
6.2.5 Neutralization of aerosol particles .10
6.2.6 Make-up air line .12
6.2.7 Test filter mounting assembly .12
6.2.8 CPC .13
6.2.9 Final filter .15
6.3 Detailed setup for test using silver nanoparticles .15
6.4 Determination of the filter medium velocity .16
7 Qualification of the test rig and apparatus.16
7.1 CPC tests .16
7.1.1 CPC — Air flow rate stability test .16
7.1.2 CPC — Zero test .17
7.1.3 CPC — Overload test . .17
7.1.4 Counting accuracy calibration .18
7.2 DEMC tests .20
7.3 Qualification of aerosol neutralization .20
7.3.1 General.20
7.3.2 Qualification of neutralization by checking the multiple charge fraction on
the particles passing through the neutralizer .20
7.3.3 Qualification of the aerosol neutralizer using corona discharge balanced
output .21
7.3.4 Qualification of neutralization according to ISO/TS 19713-1 .21
7.4 System leak checks .22
7.4.1 Air leakage tests .22
7.4.2 Visual detection by cold smoke .22
7.4.3 Pressurization of the test system .22
7.4.4 Use of high efficiency filter media .22
7.5 Uniformity of the test aerosol concentration.22
8 Test procedure .22
8.1 Determination of the correlation ratio .22
8.2 Protocol of filtration efficiency measurement .24
ISO/TS 21083-2:2019(E)
8.2.1 Preparatory checks .24
8.2.2 Equipment preparation .24
8.2.3 Aerosol generator .24
8.2.4 Aerosol generator — Neutralizer .25
8.2.5 Filter medium neutralization .26
8.2.6 Filter medium neutralization according to ISO 29461-1 .26
8.2.7 Air flow measurement .28
8.2.8 Measurement of the pressure drop .29
8.2.9 Zero count test .29
8.2.10 Air leakage test .29
8.2.11 Loading effect test .29
8.2.12 Reported values .29
8.2.13 Measurement of filtration efficiency — Silver nanoparticles .29
8.3 Test evaluation .31
8.4 Measurement protocol for one sample — Summary .31
8.4.1 Using one CPC to measure the upstream and downstream particle
concentrations .31
8.4.2 Using two CPCs to measure the upstream and downstream particle
concentrations .32
9 Maintenance items .33
10 Measurement uncertainties .34
11 Reporting results .34
11.1 General .34
11.2 Required reporting elements .35
11.2.1 General.35
11.2.2 Report summary .35
11.2.3 Report details .36
Annex A (informative) Instruments specifications .41
Annex B (informative) Statistical analysis for precision of an experiment (according to
ISO 5725-2) .44
Annex C (informative) Safety use of IPA .49
Annex D (informative) Safe handling of radioactive devices .50
Bibliography .51
iv © ISO 2019 – All rights reserved

ISO/TS 21083-2:2019(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 www .iso
.org/iso/foreword .html.
This document was prepared by the European Committee for Standardization (CEN) Technical
Committee CEN/TC 195, Air filters for general cleaning, in collaboration with ISO Technical Committee
TC 142, Cleaning equipment for air and other gases, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
A list of all parts in the ISO 21083 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.
ISO/TS 21083-2:2019(E)
Introduction
Nano-objects are discrete piece of material with one, two or three external dimensions in the nanoscale
(see ISO/TS 80004-2) and are building blocks of nanomaterials. Nanoparticles, referring to particles
with at least one dimension below 100 nm, generally have a higher mobility than larger particles.
Because of their higher mobility and larger specific surface area, available for surface chemical
reactions, they can pose a more serious health risk than larger particles. Thus, particulate air pollution
with large concentrations of nanoparticles can result in an increased adverse effect on human health
and an increased mortality (see Reference [15]).
With the increased focus on nanomaterials and nanoparticles, the filtration of airborne nanoparticles
is also subject to growing attention. Aerosol filtration can be used in diverse applications, such as air
pollution control, emission reduction, respiratory protection for human and processing of hazardous
materials. The filter efficiency can be determined by measuring the testing particle concentrations
upstream and downstream of the filter. The particle concentration may be based on mass, surface area
or number. Among these, the number concentration is the most sensitive parameter for nanoparticles
measurement. State-of-the-art instruments enable accurate measurement of the particle number
concentration in air and therefore precise fractional filtration efficiency. Understanding filtration
efficiency for nanoparticles is crucial in schemes to remove nanoparticles, and thus, in a wider context,
improve the general quality of the environment, including the working environment.
Filtration testing for nanoparticles, especially those down to single-digit nanometres, is a challenging
task which necessitates generation of a large amount of extremely small particles, and accurate sizing
and quantification of such particles. The thermal rebound remains a question for particles down to
1 nm to 2 nm (see Reference [11]). The accuracy of particle size classification is complicated by very
strong diffusion of particles below 10 nm (see References [7] and [8]). The state-of-the-art commercial
condensation particle counters for general purposes can detect particles down to 1 nm to 2 nm.
A large number of standards for testing air filters exist such as the ISO 29463 and ISO 16890 series.
The test particle range in the ISO 29463 series is between 0,04 µm and 0,8 µm, and the focus is on
measurement of the minimum efficiency at the most penetrating particle size (MPPS). The test particle
range in the ISO 16890 series is between 0,3 µm and 10 µm. The ISO 21083 series aims to standardize
the methods of determining the efficiencies of filter media, of all classes, used in most common air
filtration products and it focuses on filtration efficiency of airborne nanoparticles, especially for
particle size down to single-digit nanometres.
Advances in aerosol instruments and studies on nanoparticle filtration in the recent years provide
a solid base for development of a test method to determine effectiveness of filtration media against
airborne nanoparticles down to 3 nm range.
vi © ISO 2019 – All rights reserved

TECHNICAL SPECIFICATION ISO/TS 21083-2:2019(E)
Test method to measure the efficiency of air filtration
media against spherical nanomaterials —
Part 2:
Size range from 3 nm to 30 nm
1 Scope
This document specifies the testing instruments and procedure for determining the filtration
efficiencies of flat sheet filter media against airborne nanoparticles in the range of 3 nm to 30 nm.
The testing methods in this document are limited to spherical or nearly-spherical particles to avoid
uncertainties due to the particle shape.
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 5167 (all parts), Measurement of fluid flow by means of pressure differential devices inserted in circular
cross-section conduits running full
ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results — Part 1: General
principles and definitions
ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method
for the determination of repeatability and reproducibility of a standard measurement method
ISO 15900, Determination of particle size distribution — Differential electrical mobility analysis for aerosol
particles
ISO 27891, Aerosol particle number concentration — Calibration of condensation particle counters
ISO 29464, Cleaning of air and other gases — Terminology
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5167-1, ISO 5725-1, ISO 5725-2,
ISO 15900, ISO 27891, and ISO 29464 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/
ISO/TS 21083-2:2019(E)
3.2 Symbols and abbreviated terms
3.2.1 Symbols
Symbol Definition
A Source strength of the radioactive source
A Original source strength of the radioactive source
A Effective filtration surface area
f
C Particle concentration upstream of the filter medium
up
C Concentration of particles with the i monodisperse size upstream of the filter medium
up,i th
C Particle concentration downstream of the filter medium
down
C Concentration of particles with the i monodisperse size downstream of the filter medium
down,i th
C Concentration of particles after the second DEMC for the particles with i charge(s)
ni
d Diameter of the initial droplet including the solvent
d
d Diameter of the testing particle after complete evaporation of the solvent
p
E Filtration efficiency of the test filter medium
E Filtration efficiency of the test filter medium against the particles with the i monodisperse size
i th
e Charge of an electron
φ Volume fraction of DEHS in the solution
v
t Half-life of the radioactive source
0,5
N Total count of particles upstream of the filter medium in a certain user-defined time interval
up
Counts of particles with the i monodisperse size upstream of the filter medium in a certain user-de-
th
N
up,i
fined time interval
N Total count of particles downstream of the filter medium in a certain user-defined time interval
down
Counts of particles with the i monodisperse size downstream of the filter medium in a certain
th
N
down,i
used-defined time interval
N Total count of particles after the second DEMC for the particles with i charge(s)
ni
n Number of elementary charges
p
P Fractional penetration of the test filter medium
P Fractional penetration of particles with the i monodisperse size for the test filter medium
i th
P Penetration with the filter medium, before applying the correlation ratio
m
Measured penetration against particles with the i monodisperse size when the filter medium is
th
P
m,i
installed in the filter medium holder, before applying the correlation ratio
q Flow rate through the filter medium
q Air flow rate through the electrometer
e
R Correlation ratio
R Correlation ratio for the i monodisperse particle size, obtained as the penetration without the filter media
i th
R Resistance of resistor
es
t Time
v Filter medium velocity
f
V Voltage
x Volume of the sampled air
α Angle for the transition section in the filter medium holder
∆p Pressure drop across the filter medium
E Initial particulate efficiency of media sample
∆E Difference in particulate efficiency between E and conditioned efficiency of the media sample
c 0
λ Radioactive decay constant equal to 0,693/ t
0,5
2 © ISO 2019 – All rights reserved

ISO/TS 21083-2:2019(E)
3.2.2 Abbreviated terms
AC Alternating current
CAS Chemical abstracts service
CL Concentration limit
CMD Count median diameter
CPC Condensation particle counter
DEHS Di(2-ethylhexyl) sebacate
DEMC Differential electrical mobility classifier
DMAS Differential mobility analysing system
HEPA High efficiency particulate air
Kr Krypton
IPA Isopropyl alcohol
MPPS Most penetrating particle size
Po Polonium
PSL Polystyrene latex
RH Relative humidity
SRM Standard reference material
4 Principle
The filtration efficiency of the filter medium is determined by measuring the particle number
concentrations upstream and downstream of the filter medium. The fractional penetration, P, represents
the fraction of aerosol particles which can go through the filter medium, as shown in Formula (1):
PC= /C (1)
down up
where C and C are the particle concentrations downstream and upstream of the filter medium,
down up
respectively. Another way is to measure the particle counts upstream and downstream of the filter
medium for a certain same user-defined time interval and sampling volume rate. Then, the penetration
is the ratio between the downstream count, N , and upstream count, N , as shown in Formula (2):
down up
P = N /N (2)
down up
The filter medium efficiency, E, is the fraction of aerosols particles removed by the filter medium, as
shown in Formula (3):
E = 1 – P (3)
The filter medium efficiency is dependent on the challenge particle size. If the test is performed with a
number of monodisperse particles with different sizes, the expression for the penetration of particles
with the i monodisperse size, P , can be written as shown in Formula (4):
th i
PC= /C (4)
iidown,up,i
where C and C are the concentration of particles with the i monodisperse size upstream and
up,i down,i th
downstream of the filter medium, respectively. If the test is performed with a number of monodisperse
ISO/TS 21083-2:2019(E)
particles with different sizes, the expression for the penetration of particles with the i monodisperse
th
size, P can be written as shown in Formula (5):
i
PN= /N (5)
iidown,,up i
where N and N are the counts of particles with the i monodisperse size upstream and
up,i down,i th
downstream of the filter medium in the same user-defined time interval and sampling volume rate,
respectively. Correspondingly, the filtration efficiency, E , of the test filter medium against the particles
i
with the i monodisperse size is as shown in Formula (6):
th
E = 1 – P (6)
i i
The test particles in the range from 3 nm to 30 nm are generated by an evaporation-condensation
method. One realization of this method is the generation of silver (Ag) particles from an electrical tube
furnace.
The test particle from the generator is neutralized. The particles are mixed homogeneously with
filtered test air if necessary to achieve desired concentration and flow rate, before they are used to
challenge the test filter medium.
A specimen of the sheet filter medium is fixed in a test filter assembly and is subject to the test air
flow corresponding to the prescribed filter medium velocity. Partial flow, which is the flow that the
CPC operates with, of the test aerosol is sampled upstream and downstream of the filter medium, and
the fractional penetration is determined from the upstream and downstream number concentrations
or total numbers in user-defined time intervals. Furthermore, the measurement of the pressure drop
across the filter medium is made at the prescribed filter medium velocity.
Additional equipment is required to measure the absolute pressure, temperature and RH of the test air.
It is also needed to measure and control the air volume flow rate.
5 Test materials
5.1 General
Any aerosol used to test the filtration performance according to this test method shall only be
introduced to the test section as long as needed to test the filtration performance properties of the test
filter medium without changing the filtration performance properties of the subject test filter medium
due to loading, charge neutralization or other physical or chemical reaction.
5.2 Solid phase aerosol — Silver test aerosol as an example
Pure silver powder source – Ag (99,999 %)
Pure silver powder properties:
3 3
Density 10,49 · 10 kg/m
Melting point 1 234 K
Boiling point 2 434 K
Solubility insoluble in water
5.3 Solid phase aerosol generation method
Silver nanoparticles or nanoparticles of other materials can be used as long as the qualification
procedure is performed and the requirements are fulfilled.
4 © ISO 2019 – All rights reserved

ISO/TS 21083-2:2019(E)
Silver nanoparticles can be generated by the evaporation-condensation method (see Reference [17]).
An electric furnace is used to generate silver nanoparticles from a pure silver powder source
(99,999 %), and clean compressed air or other gases, such as nitrogen, is used as a carrier gas with
3 −6 3
flow rate of 16,7 m /s to 50·10 m /s (1 l/min to 3,0 l/min). The silver powder source located in the
centre of a heating tube is vaporized and condensed into silver nanoparticles with a relatively wide
size distribution when the air flow exits the tube furnace. For very small particles a rapid temperature
decrease may be applied at the exit of the tube furnace so as to produce particles in the desired size
range. As an example, some technical specifications regarding tube furnaces are presented in Annex A,
Tables A.1 to A.4.
Any other generator capable of producing particles in sufficient concentrations in the particle size
range of 3 nm to 30 nm so that the particle concentration upstream of the test filter medium is at least
1 000 per cm under any of the test mode, such as monodisperse or polydisperse test described in
Clause 6, can be used.
6 Test setup
6.1 General
The test setup is shown in Figure 1 for monodisperse challenge particles and in Figure 2 for
polydisperse challenge particles. When the challenge particles are monodisperse, the setup consists of
three sections: the one that produces the aerosol particles (which contains the aerosol generator), the
particle classification section (which contains the DEMC) and the particle measuring section (which
contains the CPC). When the challenge particles are polydisperse, the particle classification shall be
performed after sampling the aerosol from the upstream or downstream section.
The measurement with monodisperse particles is the reference test while the measurement with
polydisperse particles shall be qualified carefully and verified by comparison with monodisperse test
for validating the measurement procedure.
Tests using monodisperse and polydisperse aerosols should yield equivalent results if they are carried
[9]
out correctly. Japuntich et al. performed both polydisperse and monodisperse measurements down
[20]
to 20 nm to 30 nm range and showed reasonable agreement. Buha et al. compared polydisperse test
results with models down to similar size range and showed good agreement. With the particles in even
smaller size range, the size distribution measurement downstream of the filter is increasingly difficult.
ISO/TS 21083-2:2019(E)
Key
1 air or N2 through HEPA filter 7 neutralizer
2 flow controller 8 make up air with HEPA filter
3 furnace 9 CPC
4 silver 10 filter medium holder
5 excess flow with HEPA filter 11 HEPA filter on the exhaust line
6 DEMC 12 vacuum
Figure 1 — Test setup for monodisperse challenge particles
6 © ISO 2019 – All rights reserved

ISO/TS 21083-2:2019(E)
Key
1 air or N 7 DEMC
2 flow controller 8 CPC
3 furnace 9 filter medium holder
4 silver 10 HEPA filter on the exhaust line
5 flow compensation through HEPA filter 11 vacuum
6 neutralizer
Figure 2 — Test setup for polydisperse challenge particles
6.2 Specifications of setup
6.2.1 Aerosol generation system
The aerosol generation system is described in 5.3.
6.2.2 Tubing
Tubes shall be made of electrically conductive material (stainless steel, carbon-embedded silicon tubing,
etc.) in order to minimize particle losses due to electrostatic deposition. Furthermore, the tubing length
shall be minimized so as to minimize particle losses due to diffusion. The upstream and downstream
sample lines shall be nominally identical in geometry and material.
6.2.3 DEMC
6.2.3.1 Principles and specifications
The DMAS consists primarily of a bipolar charger to neutralize the charges on particles, a controller
to control flows and high-voltage, a DEMC (see Figure 3) which separates particles based on their
electrical mobilities, a particle detector, interconnecting plumbing, a computer and suitable software.
The DEMC shall be able to classify particles in the size range of 3 nm to 30 nm and fulfil the qualification
procedure described in 7.2. In case of the unipolar charger-based instrument, the manufacturer shall
ISO/TS 21083-2:2019(E)
be contacted for suitable size range, in order to avoid errors due to multiple charge effect. The losses of
the smallest particles due to diffusion within the challenge range shall be considered as well.
NOTE For more information see ISO 15900.
DEMC principles are as follows.
Particles are introduced at the circumference of a hollow tube. A radial electric field is maintained
across the outer walls of this tube and a central electrode. As the charged particles flow through the
tube, they are attracted towards the central electrode due to the electric field. These are removed
through openings in the central electrode.
Small particles require weak electric fields to move them towards the central electrode. Larger
particles require stronger fields. By adjusting the electric field, particles of a known size are attracted
towards the opening in the central rod and are removed for measurements. Thus, particles with a
narrow range of sizes can be extracted for each voltage setting. The narrowness is mainly determined
by the geometry and uniformity of air flow in the device. By stepping through a range of voltages or
electric field strengths, the number of particles in different sizes in the sample can be measured and the
particle size distribution of the sample determined.
Alternatively, since the DEMC separates particles according to their electrical mobilities, if one
knows the number of charges on a particle, it can be used to separate monodisperse particles from a
polydisperse aerosol.
In this measurement method test particles are first generated and then sent through a neutralizer.
Afterwards, the test particles have the Boltzmann equilibrium charge distribution. In this case the
singly charged particles represent the largest fraction of the charged particles (see the details in 7.3.2).
In addition the size distribution can be controlled so that the target monodisperse particle size is on
the right side of the mode of particle size distribution (see the details in 8.2.13). Under these carefully
controlled conditions it is possible to use a DEMC to classify monodisperse particles in the range of 3
nm to 30 nm. (See ISO 15900 for more details.)
A DEMC suitable for the prescribed methods in this document shall be able to separate and provide
monodisperse particles in the size range from 3 nm to 30 nm with a geometric standard deviation less
than 1,10. In general, the ratio of the sheath flow rate to the aerosol flow rate into the DEMC determines
the sizing resolution of the DEMC. A higher ratio provides more accurate sizing and avoids excessive
diffusional broadening of the particle size distribution so that better monodispersity of the aerosol
exiting the DEMC is achieved (see Reference [7]). Prescribing specifications for suitable devices are
beyond the scope of this document.
NOTE For more information on DEMC principles, see ISO 15900.
8 © ISO 2019 – All rights reserved

ISO/TS 21083-2:2019(E)
Key
1 sheath air 7 outer cylinder
2 mass flow meter 8 high voltage rod
3 neutralizer 9 excess flow
4 polydisperse aerosol 10 monodisperse flow
5 HEPA filter V high voltage power supply
6 pu
...