SIST EN ISO 25539-3:2024

SLOVENSKI STANDARD
01-december-2024
Nadomešča:
SIST EN ISO 25539-3:2012
Vsadki (implantati) za srce in ožilje - Znotrajžilni pripomočki - 3. del: Filtri "vena
cava" (ISO 25539-3:2024)
Cardiovascular implants - Endovascular devices - Part 3: Vena cava filters (ISO 25539-
3:2024)
Kardiovaskuläre Implantate - Endovaskuläre Implantate - Teil 3: Hohlvenenfilter (ISO
25539-3:2024)
Implants cardiovasculaires - Dispositifs endovasculaires - Partie 3 : Filtres caves (ISO
25539-3:2024)
Ta slovenski standard je istoveten z: EN ISO 25539-3:2024
ICS:
11.040.40 Implantanti za kirurgijo, Implants for surgery,
protetiko in ortetiko prosthetics and orthotics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 25539-3
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2024
EUROPÄISCHE NORM
ICS 11.040.40 Supersedes EN ISO 25539-3:2011
English Version
Cardiovascular implants - Endovascular devices - Part 3:
Vena cava filters (ISO 25539-3:2024)
Implants cardiovasculaires - Dispositifs Kardiovaskuläre Implantate - Endovaskuläre
endovasculaires - Partie 3 : Filtres de veine cave (ISO Implantate - Teil 3: Hohlvenenfilter (ISO 25539-
25539-3:2024) 3:2024)
This European Standard was approved by CEN on 23 August 2024.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye 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
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 25539-3:2024 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 25539-3:2024) has been prepared by Technical Committee ISO/TC 150
"Implants for surgery" in collaboration with Technical Committee CEN/TC 285 “Non-active surgical
implants” the secretariat of which is held by DIN.
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 2025, and conflicting national standards shall be
withdrawn at the latest by April 2025.
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 ISO 25539-3:2011.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 25539-3:2024 has been approved by CEN as EN ISO 25539-3:2024 without any
modification.
International
Standard
ISO 25539-3
Second edition
Cardiovascular implants —
2024-10
Endovascular devices —
Part 3:
Vena cava filters
Implants cardiovasculaires — Dispositifs endovasculaires —
Partie 3: Filtres de veine cave
Reference number
ISO 25539-3:2024(en) © ISO 2024

ISO 25539-3:2024(en)
© ISO 2024
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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 25539-3:2024(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General requirements . 5
4.1 Classification .5
4.2 Materials of construction for filter system .5
4.3 Configuration and size designation for filters . .6
4.4 Intended clinical use designation .6
5 Intended performance . 6
6 Design attributes . 6
6.1 General .6
6.2 Filter system .6
6.3 Vena cava filter .6
6.4 Optional filter .7
6.5 Convertible filter .7
6.6 Retrieval system .7
6.7 Conversion system .7
6.8 Filter system, retrieval system and conversion system .7
6.9 Coating on delivery system or filter .8
6.10 Absorbable filter or coating .8
7 Materials . 8
8 Design evaluation . 8
8.1 General .8
8.2 Sampling .9
8.3 Conditioning of test samples .10
8.4 Reporting .10
8.5 Bench and analytical tests .11
8.5.1 General .11
8.5.2 Filter system.11
8.5.3 Vena cava filter . 13
8.5.4 Optional filter . 15
8.5.5 Convertible filter .16
8.5.6 Retrieval system .16
8.5.7 Conversion system .17
8.5.8 Filter system, retrieval system and conversion system .18
8.5.9 Coating on the delivery system, the retrieval system, the conversion system or
the filter .19
8.5.10 Absorbable filter or coating .19
8.6 Preclinical in vivo evaluation . 20
8.6.1 Purpose . 20
8.6.2 Specific aims . 20
8.6.3 Protocol considerations .21
8.6.4 Data acquisition . . .21
8.6.5 Test report and additional information . 23
8.7 Clinical evaluation .24
8.7.1 Purpose .24
8.7.2 Specific aims . 25
8.7.3 Protocol considerations . 25
8.7.4 Data acquisition . . . 26
8.7.5 Final report . 29

iii
ISO 25539-3:2024(en)
9 Post-market experience .30
10 Manufacturing .30
11 Sterilization .30
11.1 Products supplied sterile . 30
11.2 Sterilization residuals . 30
12 Packaging.31
12.1 General .31
12.1.1 General .31
12.1.2 Unit container .31
12.1.3 Outer container .31
12.1.4 Shipping container .31
12.1.5 Maintenance of sterility in transit .31
12.2 Labelling .31
12.2.1 Container label .31
12.2.2 Filter systems .31
12.2.3 Retrieval systems .32
12.2.4 Conversion systems .32
12.2.5 Record label .32
12.3 Information supplied by the manufacturer . 33
12.3.1 General . 33
12.3.2 Information and instructions for use . 33
Annex A (informative) Relationship between testing requirements, device attributes and
potential failure modes, and guidance for the creation of a device evaluation strategy .35
Annex B (informative) Description of clinical effects of failure .53
Annex C (informative) Description of device effects of failure .55
Annex D (informative) Test methods .56
Annex E (informative) Examples of general issues related to the clinical use of vena cava filters .92
Bibliography .94

iv
ISO 25539-3:2024(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 150, Implants for surgery, Subcommittee
SC2, Cardiovascular implants and extracorporeal systems, in collaboration with the European Committee for
Standardization (CEN) Technical Committee CEN/TC 285, Non-active surgical implants, in accordance with
the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
The second edition cancels and replaces the first edition (ISO 25539-3:2011), which has been technically
revised.
The main changes are as follows:
— the testing and clinical use related to vena cava filters has been updated;
— the consistency in nomenclature and reporting requirements has been improved.
A list of all parts in the ISO 25539 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.

v
ISO 25539-3:2024(en)
Introduction
This document was prepared to provide guidance on the minimum requirements for vena cava filter
systems. The rationale for the requirements for bench tests and analyses to assess device performance and
safety, guidance on the identification of appropriate testing to evaluate a specific device design, and guidance
for developing test methods are provided in informative annexes. Further clarification of terminology is
provided in Annexes B, C and E.
This document has been updated to reflect current knowledge regarding the testing and clinical use related
to vena cava filters, reflected in modifications to the requirements in the main body and in the guidance
for developing test methods in Annex D. In addition, revisions have been made to improve consistency in
nomenclature and reporting and to enhance the utility of this document.
This revised document introduces methodology to identify appropriate testing and analyses applicable to
intended clinical use, design and potential failure modes for a specific vena cava filter system, designated
as the device evaluation strategy. The requirement regarding the device evaluation strategy is in the main
body. Annex A provides guidance for developing a focused device evaluation strategy table that is specific
to the unique characteristics of a device, device design modifications or changes in intended use. Annex A
also provides guidance for the development of a comprehensive device evaluation strategy table that may be
used when it is not sufficient to focus only on the unique characteristics or changes.
The guidance on the development of methods to address the requirement for evaluating fatigue and durability
through computational analyses has been modified to include recommendations regarding verification of
the solution and validation of the computational model, as well as reporting. The guidance on the model
development for simulated use has also been significantly revised to improve the clinical relevance of this
testing.
In addition to modifications to specific design evaluation requirements, guidance has been provided
regarding the assessment of the acceptability of test results. When the requirement is to quantitatively
appraise or analyse a parameter, test results generally may be compared to a quantitative value
(i.e. acceptance criteria). For characterization tests, it is appropriate to provide an explanation of the
relevance of the results. Additionally, some testing can include a comparison to test data or existing data
from a previously evaluated device.
For design evaluation, requirements regarding sampling, conditioning of test samples and reporting have
been incorporated in the main body. Guidance on these elements of testing and documentation were
previously only included in Annex D.
The revisions to the annexes to this document are given in Table 1.
Table 1 — Revisions to the annexes in this document
Annex of ISO 25539-3:2011 Changes in ISO 25539-3:2024
Annex A – Attributes of endovascular devices – Vena cava Annex A now includes the relationship between testing re-
filters – Technical and clinical considerations quirements, device attributes, and potential failure modes
and guidance for the creation of a device evaluation strategy.
Annex B – Descriptions of potential device effects of failure Annex B now includes a description of potential clinical
and failure modes and descriptions of detrimental clinical effects of failure.
effects
Annex C – Bench and analytical tests The list of tests is included in Table D.1.
Annex C now includes a description of potential device
effects of failure.
Annex D – Test methods Annex D – Test methods
Many filter systems have been shown to be safe and effective in clinical use – this update is not intended
to require additional evaluations of these devices to remain in compliance with this document as the
testing would not provide useful information regarding the expected clinical performance of the device.
Manufacturers may rely on historical data gathered under the guidance of the previous edition of this
document (i.e. ISO 25539-3:2011). Similarly, for device modifications or changes in intended clinical use, this

vi
ISO 25539-3:2024(en)
edition of this document is not intended to require additional evaluation of aspects of the device that are not
expected to change clinical performance.
NOTE The relationship between testing requirements, device attributes and potential failure modes is provided
in Clause A.1. Clause A.1 also provides general information regarding device evaluation strategies. Tables A.3 to A.9
provide the rationale for the requirements specified in this document for bench tests and analyses to assess device
performance and safety. An explanation of the table headings for Tables A.3 to A.9 is given in Table A.1.
Guidance for the creation of a device-specific evaluation strategy is provided in Clause A.2. Two approaches
to create a device-specific evaluation strategy are provided:
a) focused device evaluation strategy in A.2.1;
b) comprehensive device evaluation strategy in A.2.2.
Annex B provides a description of the potential clinical effects of failure identified in Annex A.
Annex C provides a description of the potential device effects of failure identified in Annex A.
Additional descriptions of clinical and device effects of failure are included in Annexes B and C, respectively.
Annex D provides information to consider in developing appropriate bench test and analytical methods.
Annex E provides examples of terms for clinical use related to vena cava filters.

vii
International Standard ISO 25539-3:2024(en)
Cardiovascular implants — Endovascular devices —
Part 3:
Vena cava filters
1 Scope
This document specifies the requirements for the evaluation of vena cava filter systems (filters and delivery
systems) and the requirements with respect to nomenclature, design attributes and information supplied
by the manufacturer. Guidance for the development of in vitro test methods is included in Annex D. This
document is intended to be used in conjunction with ISO 14630, which specifies general requirements for
the performance of non-active surgical implants.
NOTE 1 Due to the variations in the design of implants covered by this document, and in some cases due to the
emergence of novel types of such implants, acceptable standardized in vitro tests and clinical results are not always
available. As further scientific and clinical data become available, a revision of this document will be necessary.
This document is applicable to vena cava filters intended to prevent symptomatic pulmonary embolism
by capturing blood clots in the inferior vena cava (IVC). While this document can be useful with respect
to filters implanted in other venous locations (e.g. superior vena cava, iliac veins), it does not specifically
address the use of filters in other implantation sites.
This document is also applicable to permanent filters together with their associated delivery systems,
optional filters that can be retrieved and their associated retrieval systems, and convertible filters and
their associated conversion systems. While this document can be useful with respect to the evaluation of
repositioning filters after chronic implantation, it does not specifically address filter repositioning.
This document is not applicable to
— temporary filters (e.g. tethered) that need to be removed after a defined period of time,
— issues associated with viable tissues and non-viable biological materials, and
— procedures and devices (e.g. venous entry needle) used prior to the vena cava filter procedure.
Although absorbable filters and filters with absorbable coatings are within the scope of this document, this
document is not comprehensive with respect to the absorbable properties of these devices.
NOTE 2 Absorbable implants are covered in ISO/TS 17137.
Although coated filters and coated filter systems are within the scope of this document, this document is not
comprehensive with respect to coatings.
NOTE 3 Vascular device-drug combination products are covered in ISO 12417-1 and some coating properties are
covered in ISO 25539-4.
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 10993 (all parts), Biological evaluation of medical devices

ISO 25539-3:2024(en)
ISO 11135, Sterilization of health-care products — Ethylene oxide — Requirements for the development,
validation and routine control of a sterilization process for medical devices
ISO 11137 (all parts), Sterilization of health care products — Radiation
ISO 11607-1, Packaging for terminally sterilized medical devices — Part 1: Requirements for materials, sterile
barrier systems and packaging systems
ISO 13485, Medical devices — Quality management systems — Requirements for regulatory purposes
ISO 14630:2012, Non-active surgical implants — General requirements
ISO 14937, Sterilization of health care products — General requirements for characterization of a sterilizing
agent and the development, validation and routine control of a sterilization process for medical devices
ISO 14971, Medical devices — Application of risk management to medical devices
ISO 17665-1, Sterilization of health care products — Moist heat — Part 1: Requirements for the development,
validation and routine control of a sterilization process for medical devices
ASTM F2503, Standard Practice for Marking Medical Devices and Other Items for Safety in the Magnetic
Resonance Environment
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14630 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
absorption
action of a non-endogenous (foreign) material or substance or its degradation products
passing through or being assimilated by cells and/or tissue over time
3.2
absorbable coating
implant coating (3.20) that is intended to be absorbed
Note 1 to entry: Drugs are excluded from this definition of absorbable coatings.
3.3
access site
vein that is used for accessing the vena cava
EXAMPLE Jugular vein, femoral vein, subclavian vein, antecubital vein.
3.4
adverse event
unfavourable change in health that occurs in a subject who participates in a study while receiving the
treatment or within a specified time after receiving treatment
Note 1 to entry: For the purpose of this document, clinical effects of failure are a subset of adverse events and are
described separately.
Note 2 to entry: Adverse events are categorized by the system affected (e.g. cardiac, vascular, respiratory, neurological,
renal, gastro-intestinal) and the severity of the event.

ISO 25539-3:2024(en)
3.5
caval perforation/penetration
imaging [e.g. venography, computed tomography (CT)] showing filter components (e.g. struts, anchors)
extending more than 5 mm outside the wall of the vena cava
3.6
clinical effect of failure
specific detrimental clinical observations potentially associated with device failures
Note 1 to entry: The clinical effects of failure are described in Annex B.
3.7
clinical perforation/penetration
protrusion of filter components (e.g. struts, anchors) through the vena cava wall causing haemorrhage or
hematoma, or interacting with another organ (e.g. liver, bowel, aorta, psoas muscle, vertebral body, lymph
nodes), and resulting in adverse clinical symptoms (e.g. abdominal or back pain) or autopsy findings
3.8
conversion system
components that are intended to structurally alter a convertible filter (3.23.2) after implantation so that it no
longer functions as a filter
Note 1 to entry: A conversion system may also be used to inject contrast media (e.g. to obtain a cavagram) if indicated
in the instructions for use (IFU).
3.9
delivery system
components of the filter system (3.18) used to deliver the filter to the target position and to deploy the filter
Note 1 to entry: The delivery system may also be used to inject contrast media (e.g. to obtain a cavagram) if indicated
in the instructions for use (IFU).
3.10
determine
appraise or analyse quantitatively
Note 1 to entry: Also see evaluate (3.15).
3.11
device effect of failure
consequence to the device potentially associated with device failure
Note 1 to entry: The device effects of failure are described in Annex C.
3.12
device evaluation strategy
rationale for testing selected for a specific vena cava filter system (3.18), based on requirements of the device
design and potential failure modes (3.16)
3.13
comprehensive device evaluation strategy table
optional communication tool to present the device evaluation strategy (3.12) for a specific vena cava filter
system (3.18) that addresses attributes of failure modes (3.16)
3.14
focused device evaluation strategy table
optional communication tool to present the device evaluation strategy (3.12) for a specific vena cava filter
system (3.18) that focuses on the unique characteristics of the device design or procedure and unique
aspects of the intended use
ISO 25539-3:2024(en)
3.15
evaluate
qualitatively appraise or analyse
Note 1 to entry: Also see determine (3.10).
3.16
failure mode
type of difficulty or failure of the filter system (3.18) that can be encountered (hazards) in preclinical in vivo
or clinical use and can result in consequences (harm) to the subject
3.17
filter formation
manufacturer’s specified final expanded geometric configuration of the filter in the vena cava
3.18
filter system
component consisting of the vena cava filter (3.23) and the delivery system (3.9)
3.19
filter system orientation
orientation (e.g. jugular, femoral) of the loaded filter within the delivery system (3.9), based on the designated
access site (3.3) (e.g. jugular, femoral, subclavian, antecubital)
3.20
implant coating
surface coating (3.24) or surface modification (3.25)
Note 1 to entry: Implant coating is considered a constituent of an implant.
Note 2 to entry: A laminate, i.e. a composite material made of multiple layers of the same or different materials with
the same or different internal structures assembled sandwich-like and bonded by heat, pressure, welding, soldering
or adhesives, is not in itself considered an implant coating but the exposed surface of the laminate can be an implant
coating.
Note 3 to entry: A covering, for example additional material (e.g. a graft) added to a structure (e.g. a stent) specifically
to bridge elements of the structure for the sole purpose of reducing the permeability of the structure, is not considered
an implant coating.
[SOURCE: ISO 17327-1:2018, 3.1]
3.21
implantation site
location of vena cava filter (3.23) placement within the body
3.22
retrieval system
components that are intended to remove a specific filter
Note 1 to entry: A retrieval system may also be used to inject contrast media (e.g. to obtain a cavagram) if indicated in
the instructions for use (IFU).
3.23
vena cava filter
filter implant
transluminally placed implant, which is used to prevent pulmonary embolism by capturing blood clots
traveling in the inferior vena cava (IVC)

ISO 25539-3:2024(en)
3.23.1
absorbable filter
filter, or filter with a component, that is designed to be absorbed (3.1)
Note 1 to entry: A filter with a component designed to be absorbed can function as a convertible filter (3.23.2) without
intervention.
3.23.2
convertible filter
filter that can be altered structurally after implantation such that some permanent implant remains that no
longer functions as a filter (e.g. functions as a stent)
3.23.3
optional filter
filter that can be removed (retrievable filter) or can be left as an implant that permanently functions as a filter
3.23.4
permanent filter
filter that is designed as an implant which permanently functions as a filter
Note 1 to entry: All optional filters (3.23.3) are also permanent filters. Permanent filters can incorporate design
characteristics that allow for retrieval or conversion and can be labelled for use of these optional features, if applicable.
3.24
surface coating
layer of material with any different property than the natural surface of the substrate that is intentionally
added to the substrate
Note 1 to entry: The coating can partially or fully cover the substrate surface.
Note 2 to entry: The term includes surface coatings created as a result of additive manufacturing.
[SOURCE: ISO 17327-1:2018, 3.2]
3.25
surface modification
intentional conversion or reconstruction of the surface of the original substrate to form a new surface
material consisting of components of the substrate’s own material and possibly foreign material and forming
a surface layer with different properties
[SOURCE: ISO 17327-1:2018, 3.3]
3.26
unacceptable filter tilting
clinically significant rotation of the filter relative to the longitudinal axis of the vena cava and resulting
in performance failure (e.g. inadequate filtration, excessive filtration, filter migration, filter embolization,
caval perforation/penetration (3.5), clinical perforation/penetration (3.7), inability to retrieve the filter as
applicable, inability to convert the filter as applicable)
4 General requirements
4.1 Classification
A filter system shall be designated by its access site (see 3.3), orientation (see 3.17), implantation site (see
3.19), type (see 3.22), materials of construction, as well as surface modifications, coatings and/or drugs.
4.2 Materials of construction for filter system
Materials of the filter system (e.g. wire, imaging markers, coatings) shall be described by their generic or
chemical names.
ISO 25539-3:2024(en)
4.3 Configuration and size designation for filters
The configuration of a filter shall be designated by its geometry (e.g. conical) and whether it is p
...