EN ISO 29463-2:2018

SLOVENSKI STANDARD
01-december-2018
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SIST EN 1822-2:2010
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High-efficiency filters and filter media for removing particles in air - Part 2: Aerosol
production, measuring equipment and particle-counting statistics (ISO 29463-2:2011)
Schwebstofffilter und Filtermedien zur Abscheidung von Partikeln aus der Luft - Teil 2:
Aerosolerzeugung, Messgeräte und Partikelzählstatistik (ISO 29463-2:2011)
Filtres à haut rendement et filtres pour l'élimination des particules dans l'air - Partie 2:
Production d'aérosol, équipement de mesure et statistique de comptage de particules
(ISO 29463-2:2011)
Ta slovenski standard je istoveten z: EN ISO 29463-2:2018
ICS:
13.040.99 Drugi standardi v zvezi s Other standards related to air
kakovostjo zraka quality
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.

EN ISO 29463-2
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2018
EUROPÄISCHE NORM
ICS 91.140.30 Supersedes EN 1822-2:2009
English Version
High-efficiency filters and filter media for removing
particles in air - Part 2: Aerosol production, measuring
equipment and particle-counting statistics (ISO 29463-
2:2011)
Filtres à haut rendement et filtres pour l'élimination Schwebstofffilter und Filtermedien zur Abscheidung
des particules dans l'air - Partie 2: Production von Partikeln aus der Luft - Teil 2: Aerosolerzeugung,
d'aérosol, équipement de mesure et statistique de Messgeräte und Partikelzählstatistik (ISO 29463-
comptage de particules (ISO 29463-2:2011) 2:2011)
This European Standard was approved by CEN on 6 May 2018.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

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
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 29463-2:2018 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
The text of ISO 29463-2:2011 has been prepared by Technical Committee ISO/TC 142 "Cleaning
equipment for air and other gases” of the International Organization for Standardization (ISO) and has
been taken over as EN ISO 29463-2:2018 by Technical Committee CEN/TC 195 “Air filters for general
air cleaning” the secretariat of which is held by UNI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2019, and conflicting national standards shall be
withdrawn at the latest by April 2019.
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.
This document supersedes EN 1822-2:2009.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: 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 29463-2:2011 has been approved by CEN as EN ISO 29463-2:2018 without any
modification.
INTERNATIONAL ISO
STANDARD 29463-2
First edition
2011-10-15
High-efficiency filters and filter media for
removing particles in air —
Part 2:
Aerosol production, measuring
equipment and particle-counting
statistics
Filtres à haut rendement et filtres pour l'élimination des particules dans
l'air —
Partie 2: Production d'aérosol, équipement de mesure et statistique de
comptage de particules
Reference number
ISO 29463-2:2011(E)
©
ISO 2011
ISO 29463-2:2011(E)
©  ISO 2011
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56  CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2011 – All rights reserved

ISO 29463-2:2011(E)
Contents Page
Foreword . iv
Introduction . v
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 2
4  Aerosol production . 2
4.1  Aerosol substances . 2
4.2  Producing mono-disperse aerosols . 3
4.3  Generating poly-disperse aerosols . 6
4.4  Neutralization of aerosols . 8
4.5  Minimum performance parameters for aerosol generators . 8
4.6  Sources of error . 8
4.7  Maintenance and inspection . 8
5  Measuring devices . 9
5.1  Optical particle counters . 9
5.2  Condensation particle counter . 11
5.3  Differential mobility analyser . 14
5.4  Particle size analysis system on the basis of differential mobility analysis . 16
5.5  Dilution systems . 16
5.6  Aerosol photometer . 17
5.7  Differential pressure measuring equipment . 19
5.8  Absolute pressure measuring equipment . 19
5.9  Thermometers . 19
5.10  Hygrometer . 20
6  Maintenance and inspection intervals . 20
7  Particle counting statistics . 21
Annex A (informative) Mean size of particle size distributions . 22
Bibliography . 24

ISO 29463-2:2011(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 29463-2 was prepared by Technical Committee ISO/TC 142, Cleaning equipment for air and other gases.
ISO 29463 consists of the following parts, under the general title High-efficiency filters and filter media for
removing particles in air:
 Part 1: Classification, performance, testing and marking
 Part 2: Aerosol production, measuring equipment, particle-counting statistics
 Part 3: Testing flat sheet filter media
 Part 4: Test method for determining leakage of filter element — Scan method
 Part 5: Test method for filter elements
iv © ISO 2011 – All rights reserved

ISO 29463-2:2011(E)
Introduction
ISO 29463 (all parts) is derived from EN 1822 (all parts) with extensive changes to meet the requests from
non-EU p-members. It contains requirements, fundamental principles of testing and the marking for high-
efficiency particulate air filters with efficiencies from 95 % to 99,999 995 % that can be used for classifying
filters in general or for specific use by agreement between users and suppliers.
ISO 29463 (all parts) establishes a procedure for the determination of the efficiency of all filters on the basis of
a particle counting method using a liquid (or alternatively a solid) test aerosol, and allows a standardized
classification of these filters in terms of their efficiency, both local and overall efficiency, which actually covers
most requirements of different applications. The difference between ISO 29463 (all parts) and other national
standards lies in the technique used for the determination of the overall efficiency. Instead of mass
relationships or total concentrations, this technique is based on particle counting at the most penetrating
particle size (MPPS), which, for micro-glass filter mediums, is usually in the range of 0,12 µm to 0,25 µm. This
method also allows testing ultra-low penetration air filters, which was not possible with the previous test
methods because of their inadequate sensitivity. For membrane filter media, separate rules apply, and are
described in ISO 29463-5:2011, Annex B. Although no equivalent test procedures for testing filters with
charged media is prescribed, a method for dealing with these types of filters is described in ISO 29463-5:2011,
Annex C. Specific requirements for test method, frequency, and reporting requirements can be modified by
agreement between supplier and customer. For lower efficiency filters (group H, as described below),
alternate leak test methods noted in ISO 29463-4:2011, Annex A, can be used by specific agreement between
users and suppliers, but only if the use of these other methods is clearly designated in the filter markings as
described in ISO 29463-4:2011, Annex A.
There are differences between ISO 29463 (all parts) and other normative practices common in several
countries. For example, many of these rely on total aerosol concentrations rather than individual particles. For
information, a brief summary of these methods and their reference standards are provided in
ISO 29463-5:2011, Annex A.
INTERNATIONAL STANDARD ISO 29463-2:2011(E)

High-efficiency filters and filter media for removing particles in
air —
Part 2:
Aerosol production, measuring equipment and particle-
counting statistics
1 Scope
This part of ISO 29463 specifies the aerosol production and measuring equipment used for testing high-
efficiency filters and filter media in accordance with ISO 29463-3, ISO 29463-4 and ISO 29463-5, as well as
the statistical basis for particle counting with a small number of counted events. It is intended to be used in
conjunction with ISO 29463-1, ISO 29463-3, ISO 29463-4 and ISO 29463-5.
2 Normative references
The following referenced documents are indispensable for the application 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 29463-1, High-efficiency filters and filter media for removing particles in air — Part 1: Classification,
performance, testing and marking
ISO 29463-3, High-efficiency filters and filter media for removing particles in air — Part 3: Testing flat sheet
filter media
ISO 29463-4:2011, High-efficiency filters and filter media for removing particles in air — Part 4: Test method
for determining the leakage of filter element — Scan method
ISO 29463-5:2011, High-efficiency filters and filter media for removing particles in air — Part 5: Test method
for filter elements
1)
ISO 29464 , Cleaning equipment for air and other gases — Terminology

1) To be published.
ISO 29463-2:2011(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 29463-1, ISO 29464, and the
following apply.
3.1
counting efficiency
expression of that proportion of the particles of detectable size suspended in the volume flow under analysis
that make their way through the measured volume and are counted by the particle counter
EXAMPLE The ratio of the concentration measured to actual aerosol concentration.
NOTE The counting efficiency depends on the particle size, and decreases progressively in the proximity of the lower
detection limit of the particle counter.
4 Aerosol production
When testing a filter, a test aerosol with liquid particles shall be used as reference test method in accordance
with ISO 29463-1. Alternatively, a solid PSL aerosol may be used for local efficiency (leak) testing (see
ISO 29463-4:2011, Annex E).
The testing of high-performance filters (ISO 65 U and higher) requires methods of aerosol production with high
10 1 11 1
production rates (10 s to 10 s ), in order to provide statistically significant measurements downstream
of the filter.
By adjusting the operating parameters of the aerosol generator, it shall be possible to adjust the mean particle
diameter of the aerosol so that it is equal to the MPPS. The concentration and the size distribution of the
aerosol produced shall remain constant throughout the test.
4.1 Aerosol substances
A suitable aerosol substance for the reference test method is a liquid with a vapour pressure that is so low at
the ambient temperature that the size of the droplets produced does not change significantly due to
evaporation over the time scale relevant for the test procedure (in the order of a few seconds).
4.1.1 Possible substances include, but are not limited to,
 DEHS,
 PAO,
 paraffin oil (low viscosity).
4.1.2 The most critical properties of a possible aerosol substance are the following, which should not differ
significantly from the values given for the three substances suggested in Table 1:
 index of refraction;
 vapour pressure;
 density.
Standard laboratory safety regulations shall be observed when handling these substances. It shall be ensured
by means of suitable exhaust systems and air-tight aerosol ducting systems that the test aerosols are not
inhaled. In case of doubt, the safety data sheets for the appropriate substances shall be consulted.
2 © ISO 2011 – All rights reserved

ISO 29463-2:2011(E)
Table 1 — Important data for aerosol substances at 20 °C
a
Trivial name DEHS PAO Paraffin oil (low visc.)
Chemical designation Sebacic Poly-alpha-olefin Mixture
b
acid-bis(2-ethylhexyl) ester (e.g. CAS No. 68649-12-7) (e.g. CAS # 64742-46-7)
(e.g. CAS No. 122-62-3)
Trivial name Diethylhexylsebacate Polyalphaolefin Paraffin oil
3 c
Density, kg/m 912 800 to 820 (820 )
Melting point, K 225 280
c
Boiling point, K 529 650 to 780 (674 )
Flash point, K 473 445 to 500
Vapour pressure at 293 K,
1,9  0,1 kPa at 423 K 0,1 to 0,13 0,1
kPa
0,003 1 to 0,003 4 at 373 K
0,026
Dynamic viscosity, kg/ms 0,022 to 0,024
c
0,014 at 313 K
0,002 5 to 0,003 8 at 313 K
Kinematic viscosity, mm /s — 3,8 to 4,2 at 373 K 3,0 to 4,5 at 313 K

1,450/650
1,452/600
1,4535/550
Index of
c c
(1,455 6) (1,466 )
refraction/wavelength, nm
1,4545/500
1,4585/450
1,475/400
a
US Patents 5,059,349, 5,059,352, and 5,076,965 describe and restrict the use of PAO for filter testing.
Material properties of PAO are as given in Japan JACA Standard No. 37-2001 and ISO 14644-3.
b
CAS #, Chemical Abstract Service Registry Number, substances have been registered in Chemical Abstract, issued by American
Chemical Society.
c
Data for “Emery 3004” as a specific example of a PAO.
Source: Crosby, David W., Concentration produced by a Laskin nozzle generator, a comparison of substitute materials and DOP,
21st DOE/NRC Nuclear Air Cleaning Conference.
4.2 Producing mono-disperse aerosols
4.2.1 Condensation methods
Condensation methods are preferred for the creation of mono-disperse aerosols, i.e. the particles are formed
by condensation from the vapour phase. It is necessary to distinguish between heterogeneous and
homogeneous condensation.
4.2.1.1 Heterogeneous condensation
In the case of heterogeneous condensation, the vapour condenses at a relatively low level of super-saturation
onto very small particles that are already present, the so-called condensation nuclei. The size distribution of
the resultant aerosol has a geometrical standard deviation between   1,05 and   1,15.
g g
One type of aerosol generator that operates using the principle of heterogeneous condensation and that is
suitable for testing filters in accordance with this part of ISO 29463 is the Rapaport-Weinstock generator (see
Figure 1).
ISO 29463-2:2011(E)
4.2.1.1.1 Rapaport-Weinstock generator
NOTE See Figure 1.
An aerosol substance is nebulized through a nozzle, either as a pure substance or in solution, and the
resultant poly-disperse aerosol is then vaporized along the heated section of a glass tube. Residual nuclei of
the impurities in the material remain.

Key
1 liquid reservoir
2 nebulizer
3 vaporization section
4 thermostat
5 condensation section
a
Compressed air.
b
Aerosol.
Figure 1 — Structure of the Rapaport and Weinstock aerosol generator
In the subsequent condensation section, the aerosol substance then condenses on these nuclei to form a
mono-disperse aerosol (see also Reference [1]).
The particle diameter of this aerosol is determined by the mixing ratio of aerosol substance and solvent. The
final aerosol contains the solvent used (e.g. propanol) as a vapour.
9 1
Generators of this type achieve particle production rates of 10 s ; the particle diameter can be adjusted
between approximately 0,1 µm and 1,5 µm.
4 © ISO 2011 – All rights reserved

ISO 29463-2:2011(E)
4.2.1.2 Homogeneous condensation
At higher levels of super-saturation, clusters of vapour molecules form spontaneously without the presence of
condensation nuclei, and these then grow to particles that are some nanometres in diameter (homogeneous
condensation). Larger particles then form as a result of coagulation of these particles with one another. The
resultant size distribution has a standard deviation of   1,5 independent of the median particle size, and
g
can thus only be referred to as quasi-mono-disperse. On the other hand, rates of production of particles
achieved can be as much as two orders of magnitude larger than those possible using heterogeneous
11 1
condensation (more than 10 s ).
Figure 2 shows the structure of a free-jet condensation aerosol generator that makes use of this principle.
b
2 1
a
Key
1 DEHS tank
2 pump
3 flow controller
4 ultra-sonic nebulizer
5 thermostat
6 vaporization pipe with heater and insulation
7 sheath air
8 nozzle
9 sintered metal plate
10 coagulation section
a
Nitrogen.
b
Aerosol.
Figure 2 — Set-up of a free-jet condensation aerosol generator
ISO 29463-2:2011(E)
A pump delivers aerosol substance to an ultrasonic nebulizer at a defined rate. The relatively large ( 20 µm)
droplets that are produced are then vaporized in a heated pipe. The concentration of residual nuclei is so low
that they do not influence the subsequent homogeneous condensation process. The hot stream of nitrogen
carrying the vapour then passes through a nozzle into a cold, laminar flow of sheath air. The turbulent mixing
of the free jet with the cold air produces the super-saturation necessary for the homogeneous condensation.
The particle size and particle concentration can be adjusted by varying the volume flow rates of the aerosol
substance (DEHS), nitrogen and envelope air.
4.2.2 Particle size classification
Using a differential mobility analyser as described in 5.3, it is possible to separate a fraction with almost the
same electrical mobility from a poly-disperse aerosol (see also Reference [2]). Provided all these particles
carry only a single electrical charge, then this mono-mobile fraction is also mono-disperse. If necessary, larger
particles that carry a multiple charge, and that thus have the same electrical mobility as the single-charged
particles, shall be removed from the poly-disperse input aerosol by suitable means.
Since the proportion of singly charged particles in the relevant size range is less than 10 %, from which only a
narrow size band is selected, then the number concentration of the mono-disperse output aerosol is lower
than the input concentration by a factor of at least 100. As a consequence, this method of producing mono-
disperse aerosols is suitable only for the measurement of the particle size efficiency of the filter medium (see
ISO 29463-3).
The degree of mono-dispersity achieved by this method can be described by a geometrical standard deviation
of   1,1. In practise, however, the operating parameters are often amended to increase the particle
g
concentration at the expense of a greater standard deviation.
4.3 Generating poly-disperse aerosols
Poly-disperse liquid aerosols are usually produced by nebulizing the aerosol substance through a binary
nozzle using compressed air.
A subsequent inertial separator, in the form of baffle plates or a cyclone separator, serves to precipitate larger
particles and to reduce the range of the size distribution. The geometrical standard deviation of the distribution
generated lies between 1,6 and 2,5. The particle diameter can be influenced to a small degree by changing
the operating pressure of the nozzle. Greater influence on the particle size is usually achieved by dissolving
the aerosol in a volatile solvent (e.g. propanol) before nebulization. When the solvent evaporates, it leaves
behind particles whose size is governed by the ratio of aerosol substance to solvent that was used.
It is comparatively simple to increase the particle production rate by using a number of jets in parallel.
10 1
The maximum rate of particle production that can be achieved using one nozzle is 5  10 s .
NOTE A typical jet nebulizer is described, for example, in Reference [3].
Where higher aerosol outputs are desired (ISO 29463-5), a Laskin Nozzle aerosol generator is recommended.
4.3.1 Laskin Nozzle poly-disperse aerosol generator
The Laskin Nozzle aerosol generator system uses a nozzle to generate a poly-disperse aerosol from a liquid,
such as DOP, DEHS or PAO and employs a source of compressed gas (see also Reference [4]). The
generator creates an aerosol having a mass mean diameter of approximately 0,45 µm, a light-scattering
geometric diameter of approximately 0,72 µm, and a light-scattering mean droplet-size distribution as shown
in Figure 3 (see also Reference [4]).
6 © ISO 2011 – All rights reserved

ISO 29463-2:2011(E)
Key
1 brass tubing, 9,5 mm (3/8 in) OD  1,7 mm (0,065 in) wall
2 brass collar, 15,9 mm (5/8 in ) OD, silver brazed to tubing 1
3 radial holes, 1 mm (0,04 in) diameter, 1,6 rad (90°) apart; top edge of holes just touching bottom of collar (4 required)
4 brass plug – Silver braze in place (full penetration)
5 2 mm (0,08 in) diameter longitudinal holes next to tube in line with radial holes (4 required)
a
Approximately 12,7 mm (1/2 in) above bottom of can.
b
Length variable to suit installation.
c
Tolerances are 0,05 mm for the dimensions on the holes.
d
Tolerances are 0,51 mm for all other dimensions.
[4]
Figure 3 — Details of a Laskin Nozzle
ISO 29463-2:2011(E)
4.3.2 Laskin Generator — Verification of pressure-flow characteristics
Detailed procedures are found in IEST RP CC013. An additional gravimetric sampling method is also included
to determine the actual challenge in micrograms per litre generated by each Laskin nozzle.
4.4 Neutralization of aerosols
Since electrically charged particles are removed more effectively by filters than are uncharged particles,
electrically neutral particles should be used for testing filters. A neutral state of charge is generally understood
to be the stationary equilibrium achieved when charged aerosol particles are brought together with a sufficient
number of positive and negative gas ions. This is usually carried out by ionizing the carrier gas of the aerosol
using a radioactive source or by a corona discharge. The low level of residual charge in the aerosol after this
neutralization can be neglected for the filtration process.
Aerosol particles become electrically charged when there is a division of charges in the course of production
(e.g. nebulization). This occurs, above all, in the case when polar liquids such as water (or, to a lesser extent,
propanol) are nebulized. In the case of pure DEHS or DOP, relatively few charges occur. Condensation
processes without prior nebulization generate virtually charge-free aerosols, which do not have to be
neutralized.
In order to ensure neutralization of the highly concentrated aerosols required for testing filters, it is necessary
for the neutralizers to have a sufficiently high concentration of ions. The aerosol shall also be kept in the
ionizing atmosphere for a sufficiently long period (see also Reference [5]).
4.5 Minimum performance parameters for aerosol generators
The following apply:
a) generators for testing media:
6 1 8 1
1) particle production rate: 10 s to 10 s ,
2) particle diameter adjustable over the range: 0,04 µm to 1,0 µm;
a) generators for testing filter elements:
8 1 11 1
1) particle production rate: 10 s to 10 s ,
2) particle diameter adjustable over the range: 0,08 µm to 1,0 µm.
4.6 Sources of error
Care shall be taken that the pressure of the gas supply for the aerosol generators (compressed air, nitrogen)
remains constant. The supplied gas shall be free of particles and of a sufficiently low humidity.
Nebulizer nozzles can gradually become blocked, leading to unnoticed changes in the nebulization
characteristics.
Condensation generators are sensitive to variations in temperature along the condensation path arising, for
example, due to draughts. Further aerosol substances that are subjected to higher temperatures for long
periods can undergo changes in their physical and chemical properties and, hence, should be replaced at
regular intervals.
4.7 Maintenance and inspection
Aerosol generators shall be maintained regularly in accordance with the manufacturer's instructions.
Suitable measuring systems in accordance with Clause 5 shall be used to check the size distribution and the
constancy of the production rate at the intervals specified in Clause 6.
8 © ISO 2011 – All rights reserved

ISO 29463-2:2011(E)
5 Measuring devices
5.1 Optical particle counters
5.1.1 Operation
In an optical particle counter, the particles are led individually through an intensively illuminated measuring
volume. When passing through the measuring volume, the particle scatters light, which is detected at a
defined spatial angle by a photo detector and transformed into an electrical pulse. The level of this pulse
corresponds to the size of the particle, and the number of pulses per unit time with the particle concentration
in the air volume analysed.
Figure 4 shows an example of the general structure of an optical particle counter with a laser light source.

Key
1 reference detector
2 laser mirror
3 He-Ne laser
4 Brewster-window
5 gasket ring
6 aspherical lens
7 photo detector
8 aerosol outlet
9 parabolic mirror
10 aerosol inlet
11 aerosol nozzle
a
Sheath air.
Figure 4 — Structure of an optical particle counter — Example
ISO 29463-2:2011(E)
5.1.2 Minimum performance parameters
The following apply.
a) Optical particle counters should comply with requirements in ISO 21501-1 and/or ISO 21501-4.
b) Measuring range for the particle size: 0,1 µm to 2,0 µm (for 50 % counting efficiency) with at least one
channel with a mean size smaller than the MPPS of the filter under test; preferably half the size of MPPS.
c) Minimum number of particle size classes between 0,1 µm and 0,3 µm:
1) for testing the filter medium, five size classes;
2) for testing the filter element, two size classes. From a practical point of view, the 0,1 to 0,2 and 0,2 to
0,3 channel size ranges common to many commercial counters can meet this requirement.
1
d) Zero count rate: 1 min .
5.1.3 Sources of error and limit errors
The particle size determined by an optical particle counter is a scattered-light equivalent diameter (see also
Reference [7]), which is dependent not only on the geometrical particle size but also on the shape of the
particle and the optical properties of the particle material. The nature of this dependency varies according to
the constructional type of the particle counter. Measurement results can be compared between two different
particle counters only if these have been calibrated for the particle material in question.
If the particle concentration is too high, so-called coincidence errors occur. This means that several particles
enter the measuring volume at the same time, and are interpreted as one larger particle. Suitable dilution
measures shall be adopted (see 5.5) to ensure that the maximum concentration is not exceeded. The
maximum concentration for a specific particle counter can be determined by generating an aerosol at a
constant rate into a known volume of air. The concentration should provide approximately 20 000 counts per
minute to 30 000 counts per minute in a precise measured volume of air. Once the concentration is
determined, continue the same particle generation but reduce the airflow volume. Using Equation (1),
compare the new higher measured concentration to calculated concentration.
C  V  C  V (1)
c c m m
where
C is the calculated concentration;
c
V is the calculated volume;
c
C is the measured concentration;
V is the measured volume.
If the measured and calculated values correspond, repeat the procedure at a new, lower airflow rate. Continue
the process until the measured concentration is 95 % of the calculated concentration. This is the maximum
aerosol concentration that can be measured with that counter with a 5 % coincidence loss.
The volume flowmeter on the counter shall be calibrated against a traceable standard.
10 © ISO 2011 – All rights reserved

ISO 29463-2:2011(E)
5.1.4 Maintenance and inspection
Optical particle counters shall be regularly maintained and inspected by qualified personnel. This also includes
a calibration using PSL (polystyrene latex) aerosols.
The inspection of the correct operation by the user shall include a check of the flow rate, as well as a regular
check of the zero count rate by inserting a suitable upstream filter of class ISO 35 H or higher.
If several counters are available, a further operational check is possible by comparative measurements of a
test aerosol.
5.1.5 Calibration
Optical particle counters are normally calibrated using PSL particles (see also References [8] and [9]). A
calibration with other, usually liquid aerosol materials (e.g. DEHS) is possible using a vibrating orifice aerosol
generator (see also Reference [10]) or independent aerosol sizing equipment.
The determination of the counting efficiency requires the production of mono-disperse aerosols of known
concentration (e.g. with the aid of a differential mobility analyser and an aerosol electrometer or condensation
particle counter (see also Reference [2]), so that this is usually possible only in well-equipped aerosol
laboratories. As an alternative, the counting efficiency can also be tested using PSL aerosols by means of
comparative measurements with another optical particle counter. In this case, the lower measuring limit of the
comparison counter shall be lower than that of the counter being calibrated.
5.2 Condensation particle counter
5.2.1 Operation
In a condensation particle counter (CPC), particles that are too small for direct optical measurement are
enlarged by condensation of a vapour before being subjected to light scattering or light extinction
measurements. The concentration of the resultant droplets is determined by counting or by photometry.
However, using this method, the information about the original size of the particles is lost.
The super-saturation required for the vapour condensation can be produced for CPCs with continuous flow in
two ways.
The first is that the aerosol is first saturated with the vapour at a temperature above the ambient temperature,
and then cooled by contact with a cold pipe wall (external cooling) (see also Reference [11]). Figure 5 shows
the structure of such a device. The aerosol flows through a pipe in which it is saturated with butanol vapour,
and then through a condensation pipe in which it is cooled from outside. The resultant drops are then
registered by a scattered light sensor.
In the second case, the aerosol at ambient temperature is mixed with a warmer, particle-free, vapour
saturated air flow. The mixing leads to super-saturation and condensation (see also Reference [12]). This
principle is shown in Figure 6.
Here the aerosol is led directly to a mixing nozzle by the shortest route. The drops of propylene glycol that
form along the condensation section are again registered by a scattered light sensor.
ISO 29463-2:2011(E)
Key
1 aerosol inlet
2 condensation pipe
3 thermal insulation
4 laser diode
5 lens system
6 aerosol outlet
7 nozzle
8 photo detector
9 analogue signal
10 digital signal
11 peltier element
12 heat sink (free convection)
13 saturation tube and alcohol reservoir
Figure 5 — Structure of a condensation particle counter using the principle of external cooling
12 © ISO 2011 – All rights reserved

ISO 29463-2:2011(E)
Key
1 aerosol inlet
2 laser diode
3 aperture
4 photo detector
5 light trap
6 condensation section
7 mixing nozzle
8 vapour inlet
Figure 6 — Structure of a condensation particle counter using the mixing principle
5.2.2 Minimum performance parameters
The following apply:
 measuring range for the particle size: 50 nm to 0,8 µm (for 100 % counting efficiency);
1
 zero count rate: 1 min .
5.2.3 Sources of error and limit errors
If a CPC is used in the counting mode, then the determination of the particle concentration depends primarily
on the accuracy of the sampling volume flow rate. Depending on the measuring or control method used, this
lies between 2 % and 5 %.
In the photometric mode of operation, the relationship between the number concentration and the output
signal also depends on the size of the droplets produced. Operation in the photometric mode should be
avoided because, in extreme cases, the measuring inaccuracies can be as large as 100 % (see also
References [13] and [14]).
ISO 29463-2:2011(E)
5.2.4 Maintenance and inspection
The level of the vapour substance in the reservoir shall be checked at regular intervals. The vapour substance
shall be exchanged at intervals, since water accumulates in it and changes its thermodynamic properties.
The inspection of correct operation shall include a check of the flow, as well as a regular check of the zero
count rate by inserting a suitable upstream filter of class ISO 35 H or higher.
If several counters are available, a further operational check is possible by comparative measurements of a
test aerosol.
5.2.5 Calibration
A condensation particle counter operating in the counting mode can be regarded as an independent
measuring method that requires nearly no calibration. It is necessary to check only the sampling volume flow
from time to time by comparison, for example, with a floating element flowmeter.
The calibration of a CPC in its photometric mode and the determination of its counting efficiency require the
production of mono-disperse aerosols of known concentration (using a differential mobility analyser and an
aerosol electrometer; see also Reference [2]) and is usually possible only in well-equipped aerosol
laboratories.
5.3 Differential mobility analyser
5.3.1 Operation
In a differential mobility analyser (DMA), particles can be classified according to their electrical mobility. The
electrical mobility of a particle is a function of the particle size and the number of electrical charges on the
particle. Figure 7 shows the structure of a DMA.
The mobility analyser itself consists of two concentric cylindrical electrodes. The poly-disperse aerosol being
classified is first brought to a defined state of electrical charge by the attachment of gas ions, and finally
introduced through a narrow circular gap along the outer electrode into the DMA. Isokinetic, particle-free air is
introduced along the inner electrode. Under the influence of an electric field between the electrodes, particles
with a single charge migrate at right angles to the flow direction towards the central electrode, whereas the
particles with the opposite charge polarity are attracted to the outer electrode. At the lower end of the inner
electrodes is a narrow slit through which a partial flow of particles with a defined electrical mobility is extracted.
An appropriate choice of size distribution of the poly-disperse primary aerosol ensures that these particles all
have only a single electrical charge and are thus of the same size.
5.3.2 Minimum performance parameters
The following apply:
 operational particle size range: 10 nm to 0,8 µm;
 geometrical standard deviation of the (quasi) mono-disperse aerosol: 1,3.
5.3.3 Sources of error and limit errors
If the size distribution of the primary aerosol is not precisely adapted to the size of the mono-disperse output
aerosol, then in the particle size range above 0,1 µm there can be a considerable proportion of larger particles
with multiple charges in the output aerosol.
Leaks and maladjusted volume flow rates can lead to a drift from the selected particle size and inadequate
mono-dispersity.
14 © ISO 2011 – All rights reserved

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