High-efficiency filters and filter media for removing particles in air - Part 3: Testing flat sheet filter media (ISO 29463-3:2011)

ISO 29463-3:2011 specifies the test procedure for testing the efficiency of flat sheet filter media. It is intended for use in conjunction with ISO 29463-1, ISO 29463-2, ISO 29463-4 and ISO 29463-5.

Schwebstofffilter und Filtermedien zur Abscheidung von Partikeln aus der Luft - Teil 3: Prüfung des planen Filtermediums (ISO 29463-3:2011)

Dieser Teil der ISO 29463 spezifiziert das Verfahren für die Prüfung des Abscheidegrads von planen Filtermedien. Er sollte in Verbindung mit ISO 29463 1, ISO 29463 2, ISO 29463 4 und ISO 29463 5 verwendet werden.

Filtres à haut rendement et filtres pour l'élimination des particules dans l'air - Partie 3: Méthode d'essai des filtres à feuille plate (ISO 29463-3:2011)

La présente partie de l'ISO 29463 spécifie le mode opératoire pour les essais d'efficacité des filtres à feuille plate. Elle est destinée à être utilisée conjointement avec l'ISO 29463‑1, l'ISO 29463‑2, l'ISO 29463‑4 et l'ISO 29463‑5.

Zelo učinkoviti filtri in filtrirno sredstvo za odstranjevanje delcev iz zraka - 3. del: Preskušanje ravnih filtrskih medijev (ISO 29463-3:2011)

ISO 29463-3:2011 določa preskusni postopek za preskušanje učinkovitosti ravnih filtrskih medijev. Predviden je za uporabo v povezavi s standardi ISO 29463-1, ISO 29463-2, ISO 29463-4 in ISO 29463-5.

General Information

Status
Published
Public Enquiry End Date
31-Mar-2018
Publication Date
24-Oct-2018
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
18-Oct-2018
Due Date
23-Dec-2018
Completion Date
25-Oct-2018

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SLOVENSKI STANDARD
SIST EN ISO 29463-3:2018
01-december-2018
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SIST EN 1822-3:2010

=HORXþLQNRYLWLILOWULLQILOWULUQRVUHGVWYR]DRGVWUDQMHYDQMHGHOFHYL]]UDNDGHO

3UHVNXãDQMHUDYQLKILOWUVNLKPHGLMHY ,62

High-efficiency filters and filter media for removing particles in air - Part 3: Testing flat

sheet filter media (ISO 29463-3:2011)

Schwebstofffilter und Filtermedien zur Abscheidung von Partikeln aus der Luft - Teil 3:

Prüfung des planen Filtermediums (ISO 29463-3:2011)

Filtres à haut rendement et filtres pour l'élimination des particules dans l'air - Partie 3:

Méthode d'essai des filtres à feuille plate (ISO 29463-3:2011)
Ta slovenski standard je istoveten z: EN ISO 29463-3:2018
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
SIST EN ISO 29463-3:2018 en,fr,de

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

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SIST EN ISO 29463-3:2018
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SIST EN ISO 29463-3:2018
EN ISO 29463-3
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2018
EUROPÄISCHE NORM
ICS 91.140.30 Supersedes EN 1822-3:2009
English Version
High-efficiency filters and filter media for removing
particles in air - Part 3: Testing flat sheet filter media (ISO
29463-3:2011)

Filtres à haut rendement et filtres pour l'élimination Schwebstofffilter und Filtermedien zur Abscheidung

des particules dans l'air - Partie 3: Méthode d'essai des von Partikeln aus der Luft - Teil 3: Prüfung des planen

filtres à feuille plate (ISO 29463-3:2011) Filtermediums (ISO 29463-3:2011)
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 29463-3:2018 E

worldwide for CEN national Members.
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SIST EN ISO 29463-3:2018
EN ISO 29463-3:2018 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 29463-3:2018
EN ISO 29463-3:2018 (E)
European foreword

The text of ISO 29463-3:2011 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 29463-3:2018 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 1822-3:2009.

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 29463-3:2011 has been approved by CEN as EN ISO 29463-3:2018 without any

modification.
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SIST EN ISO 29463-3:2018
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SIST EN ISO 29463-3:2018
INTERNATIONAL ISO
STANDARD 29463-3
First edition
2011-10-15
High-efficiency filters and filter media for
removing particles in air —
Part 3:
Testing flat sheet filter media
Filtres à haut rendement et filtres pour l'élimination des particules dans
l'air —
Partie 3: Méthode d'essai des filtres à feuille plate
Reference number
ISO 29463-3:2011(E)
ISO 2011
---------------------- Page: 7 ----------------------
SIST EN ISO 29463-3:2018
ISO 29463-3:2011(E)
COPYRIGHT PROTECTED DOCUMENT
© 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
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SIST EN ISO 29463-3:2018
ISO 29463-3:2011(E)
Contents Page

Foreword ............................................................................................................................................................ iv

Introduction ......................................................................................................................................................... v

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

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

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

4  Symbols and abbreviations .................................................................................................................. 1

5  Principle ................................................................................................................................................. 3

6  Sampling of sheet filter media ............................................................................................................. 3

7  Test apparatus ....................................................................................................................................... 3

7.1  Test arrangements for testing with mono-disperse test aerosol ..................................................... 5

7.2  Test arrangements for testing with a poly-disperse test aerosol .................................................... 5

7.3  Test filter mounting assembly ............................................................................................................. 7

7.4  Determination of the filter medium face velocity ............................................................................... 8

8  Requirements for the test air ............................................................................................................... 8

9  Testing procedure ................................................................................................................................. 9

9.1  Preparatory checks ............................................................................................................................... 9

9.2  Procedure ............................................................................................................................................... 9

9.3  Reference test method ........................................................................................................................ 10

10  Evaluation ............................................................................................................................................ 10

11  Test report ............................................................................................................................................ 11

12  Maintenance and inspection of the test apparatus .......................................................................... 11

13  Production test for media ................................................................................................................... 12

13.1  Measurement of differential pressure ............................................................................................... 12

13.2  HEPA filter media penetration test .................................................................................................... 12

14  Physical property test of filter media ................................................................................................ 12

Annex A (informative) Example of an application with evaluation .............................................................. 13

Annex B (informative) Production testing of filter media ............................................................................. 17

Annex C (informative) Media physical properties ......................................................................................... 18

Bibliography ...................................................................................................................................................... 20

© ISO 2011 – All rights reserved iii
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SIST EN ISO 29463-3:2018
ISO 29463-3:2011(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 29463-3 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
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SIST EN ISO 29463-3:2018
ISO 29463-3:2011(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 they

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 described 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.
© ISO 2011 – All rights reserved v
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SIST EN ISO 29463-3:2018
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SIST EN ISO 29463-3:2018
INTERNATIONAL STANDARD ISO 29463-3:2011(E)
High-efficiency filters and filter media for removing particles in
air —
Part 3:
Testing flat sheet filter media
1 Scope

This part of ISO 29463 specifies the test procedure for testing the efficiency of flat sheet filter media. It is

intended for use in conjunction with ISO 29463-1, ISO 29463-2, 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 29463-1:2011, High-efficiency filters and filter media for removing particles in air — Part 1: Classification,

performance, testing and marking

ISO 29463-2:2011, High-efficiency filters and filter media for removing particles in air — Part 2: Aerosol

production, measuring equipment, particle-counting statistics

ISO 29463-4:2011, High-efficiency filters and filter media for removing particles in air — Part 4: Test method

for determining 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
ISO 29464 , Cleaning equipment for air and other gases — Terminology
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 29463-1, ISO 29463-2 and

ISO 29464 apply.
4 Symbols and abbreviations

Table 1 presents the quantities (terms and symbols) used in this part of ISO 29463 to represent measurement

variables and calculated values. The values should be inserted in the equation given for these calculations in

the units specified.
1) To be published.
© ISO 2011 – All rights reserved 1
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SIST EN ISO 29463-3:2018
ISO 29463-3:2011(E)
Table 1 — Quantities, symbols and units
Equation for the
Term Symbol Unit
calculation
Measured variables
Exposed area A
 3
Test volume flow rate V
cm /s
Pressure drop p Pa
Mean particle diameter µm
Particle number N —
 3
Sampling volume flow rate cm /s
Sampling duration t s
Calculated quantities
Filter medium face velocity u cm/s u
Δp ΔΔp p
Mean differential pressure Pa
 i
i1
3 c 
Particle number concentration
N cm N
Vt
Ni,d,
P a P 
Penetration for particles in size range i
i i
Ni,u,
Mean penetration PP
 i
i1
Mean efficiency E EP1
Number of particles for the upper or lower ISO 29463-2:2011,
95 %
limit of the 95 % level of confidence Clause 7
Ni,d,95 %,
Penetration as upper limit value for the
P 
P a
95 %,i
95 %,i
95 % level of confidence c
Ni,u,95 %,
Mean penetration as upper limit value for
P a
PP
95 % 95 %  95 %,i
the 95 % level of confidence
i1
Mean efficiency as lower limit value for the
E a EP1
95 % 95 % 95 %
95 % level of confidence
These quantities are usually given as a percentage.

The index, u, refers to upstream particle counts, and the index, d, refers to downstream particle counts.

2 © ISO 2011 – All rights reserved
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SIST EN ISO 29463-3:2018
ISO 29463-3:2011(E)
5 Principle

When testing the sheet filter medium, the particle size efficiency is determined using a particle counting

method. The testing may use a mono-disperse or a poly-disperse test aerosol. The methods differ in terms of

both the production of the aerosol and the particle counter used. Furthermore, the measurement of the

pressure drop is made at the prescribed filter medium velocity.

Specimens of the sheet filter medium are fixed in a test filter assembly and subjected to the test air flow

corresponding to the prescribed filter medium velocity. The test aerosol from the aerosol generator is

conditioned (e.g. vaporization of a solvent), then neutralized, mixed homogeneously with filtered test air and

directed to the test filter assembly.

In order to determine the efficiency, partial flows of the test aerosol are sampled upstream and downstream of

the filter medium. Using a particle counting instrument, the number concentration of the particles contained is

determined for various particle sizes. The results of these measurements are used to draw a graph of

efficiency against particle size for the filter medium, and to determine the particle size for which the efficiency

is a minimum. This particle size is known as the most penetrating particle size (MPPS).

When measuring the particles on the upstream side of the filter medium, it can be necessary to use a dilution

system in order to reduce the concentration of particles down to the measuring range of the particle counter

used.

Additional equipment is required to measure the absolute pressure, temperature and relative humidity of the

test aerosol and to measure and control the test volume flow rate.
6 Sampling of sheet filter media

The testing of the sheet filter medium shall be carried out on at least five samples.

The samples shall be handled with care; the area being tested shall be free from all folds, kinks, holes or other

irregularities.
All samples shall be clearly and permanently marked with the following details:
a) designation of the filter medium;
b) upstream side of the filter medium.
7 Test apparatus

The test apparatus being used and the arrangement of the components and measuring equipment are shown

in Figure 1.

The basic details for the aerosol generation and the aerosol neutralization, together with the details of suitable

types of apparatus, are given in ISO 29463-2.
© ISO 2011 – All rights reserved 3
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SIST EN ISO 29463-3:2018
ISO 29463-3:2011(E)
Key
1 filter 9 differential pressure gauge
2 pressure valve 10 dilution system
3 solenoid valve 11 condensation particle counter

4 jet nebulizer 12 measuring equipment for absolute pressure, temperature and relative humidity

5 neutralizer 13 volume flow rate meter
6 differential mobility analyser 14 vacuum pump
7 needle valve 15 computer for control and data storage
8 test filter mounting assembly
Figure 1 — Set-up for testing with mono-disperse test aerosols
4 © ISO 2011 – All rights reserved
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SIST EN ISO 29463-3:2018
ISO 29463-3:2011(E)
7.1 Test arrangements for testing with mono-disperse test aerosol

When testing sheet filter media with a mono-disperse test aerosol, the particle number concentration is

determined using a total count method with a condensation particle counter. The arrangement of the test

apparatus is shown in Figure 1.

The mono-disperse test aerosol is created in a number of steps. Firstly, a poly-disperse primary aerosol is

produced using a jet nebulizer with, for example, a DEHS- or DOP-iso-propanol solution. The particles are

reduced to a convenient size for the following process by evaporation of the solvent. The aerosol is then

neutralized and passed to a differential mobility analyser. The quasi-mono-disperse test aerosol available at

the output of the differential mobility analyser is once again neutralized, and then mixed homogeneously with

filtered test air in order to achieve at the test volume flow rate required for the filter medium velocity.

The mean particle diameter of the number distribution is varied by adjusting the voltage between the

electrodes of the differential mobility analyser .

In order to achieve a sufficiently high particle number concentration over the entire test range from 0,04 µm to

0,8 µm, it can prove necessary to use several jet nebulizers with differing concentrations of the aerosol

substances in the solvent. Numerical concentrations that are too high can be adjusted by diluting the test

aerosol before the test filter mounting assembly. The number concentration in the test aerosol shall be

selected so that no dilution is necessary for the measurements made downstream from the filter.

A pump positioned downstream draws the test aerosol through the test filter mounting assembly. This ensures

that the differential mobility analyser can always operate under nearly the same conditions, independent of the

pressure drop across the tested filter medium. In contrast, the testing system operates with an overpressure,

which ensures that leaks in the system do not falsify the test measurements.

Particles are counted upstream and downstream from the filter using either two condensation particle counters

in parallel, or using only one such counter to measure the upstream and downstream concentrations

alternately. If the level of the upstream number concentration exceeds the measuring range of the counter,

then a dilution system shall be included between the sampling point and the counter.

7.2 Test arrangements for testing with a poly-disperse test aerosol

When testing sheet filter media with a poly-disperse test aerosol, optical particle counters that determine the

number distribution and the number concentration of the test aerosol are used.

The tests can be carried out directly with the poly-disperse, neutralized primary aerosol. In order to cover the

test range, it can be necessary to use several jet nebulizers with different concentrations of the aerosol

substance in the solvent. The mean particle diameter of the number distribution shall not lie outside the test

range of the particle counter used.

The arrangement of the test apparatus is shown in Figure 2. Instead of the single or two parallel condensation

particle counters (CPC), optical particle counters are used to determine the number distribution and the

number concentration of the poly-disperse test aerosol on the upstream and downstream sides of the filter

medium.

When testing with a poly-disperse test aerosol and particle counting and sizing equipment, it is also necessary

to ensure that the number concentration of the test aerosol is adjusted to suit the measuring range of the

particle counter, if necessary by the inclusion of a dilution system.

2) The adjustment gives the mode of number distribution. This can be taken as equal to the median value with sufficient

accuracy.
© ISO 2011 – All rights reserved 5
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SIST EN ISO 29463-3:2018
ISO 29463-3:2011(E)
Key
1 filter
2 pressure reduction valve
3 jet nebulizer
4 neutralizer
5 test filter mounting assembly
6 differential pressure gauge
7 dilution system
8 optical particle counter
9 needle valve
10 vacuum pump
11 measuring equipment for absolute pressure, temperature and relative humidity
12 volume flow rate meter
13 computer for control and data storage
Figure 2 — Set-up for testing with poly-disperse test aerosols
6 © ISO 2011 – All rights reserved
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SIST EN ISO 29463-3:2018
ISO 29463-3:2011(E)
7.3 Test filter mounting assembly

The test filter mounting assembly consists of a moveable upper section and a fixed lower section (an example

is shown in Figure 3). The sheet filter medium shall have a circular exposed area of 100 cm . The filter

medium shall be mounted in such a way that the measurements obtained are not influenced by by-pass leaks.

Where seals are used for this purpose, they shall not change the exposed area.

The test aerosol is introduced through the inlet opening in the upper section of the test filter mounting

assembly. It shall be ensured that the test aerosol to which the filter medium is exposed possesses a

homogeneous local concentration over the entire passage area (standard deviation   10 %). An outlet for

the test aerosol is provided in the base section of the test filter mounting assembly.

Further connections are provided for sampling of partial flows of the test aerosol on the upstream side and

downstream side to measure the particles, as well as for the measurement of the pressure drop.

All the materials of the test filter mounting assembly with which the test aerosol comes into contact shall be

kept clean, and shall be easy to keep clean, shall be resistant to corrosion, shall conduct electricity and shall

be earthed (electrically grounded). Stainless steel and anodized aluminium shall preferably be used. The test

filter mounting assembly may have any appropriate constructional form, but shall meet all the test

requirements specified in this part of ISO 29463.
Key
1 upper section (moveable)
2 lower section (fixed)
3 inlet for the test aerosol
4 outlet for the test aerosol
5 upstream sampling part
6 downstream sampling part
7 measurement points for differential pressure
Figure 3 — Test filter mounting assembly — Example
© ISO 2011 – All rights reserved 7
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SIST EN ISO 29463-3:2018
ISO 29463-3:2011(E)
7.3.1 Measurement of differential pressure

The differential pressure across the sheet filter medium is measured using differential pressure measuring

equipment (see ISO 29463-2) which is attached to the upstream and downstream differential pressure

measuring points of the test filter mounting assembly. At the measuring points the static pressure shall be

measured.

The measuring points shall be arranged at right angles to the inner surface of the test filter mounting assembly

so that as far as possible the measurements are not influenced by the flow rate. The inner edges of the drill

holes must be sharp-edged and free of burrs. The connections from the measurement points to the pressure

gauge shall be leakproof and clean.
7.3.2 Sampling

For the sampling of the test aerosol on the upstream and downstream sides, it shall be ensured that the partial

flows contain representative number particle concentrations. Given the small particle sizes being measured in

the testing, isokinetic sampling is not absolutely necessary at this point.

The connections from the sampling point to the measuring apparatus shall be kept clean, shall be

...

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