ISO 5371:2025

FINAL DRAFT
International
Standard
ISO/FDIS 5371
ISO/TC 142
Containment high efficiency
Secretariat: UNI
filtration unit (CHEFU) in
Voting begins on:
ventilation system of biosafety
2025-04-28
facilities
Voting terminates on:
2025-06-23
Unités de filtration à très haute efficacité de confinement
(CHEFU) dans le système de ventilation des installations de
biosécurité
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 5371:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 5371:2025(en)
International
Standard
ISO/FDIS 5371
ISO/TC 142
Containment high efficiency
Secretariat: UNI
filtration unit (CHEFU) in
Voting begins on:
ventilation system of biosafety
facilities
Voting terminates on:
Unités de filtration à très haute efficacité de confinement
(CHEFU) dans le système de ventilation des installations de
biosécurité
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
ISO/FDIS 5371:2025(en) © ISO 2025

ii
ISO/FDIS 5371:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Design and construction . 3
5 Requirements . 3
5.1 Appearance .3
5.2 Resistance to air flow .3
5.3 Vacuum deformation test .4
5.4 Air tightness .4
5.5 Leakage test of the installed HEPA filter . .4
5.6 Decontamination .4
5.7 Leakage identification .4
6 Test methods . 4
6.1 Appearance .4
6.2 Resistance to air flow .5
6.3 Vacuum deformation test .5
6.4 Air tightness .5
6.5 Leakage test of the installed HEPA filter . .5
6.5.1 Test aerosol .5
6.5.2 Test apparatus .6
6.5.3 Scanning leak test.6
6.5.4 Total penetration leakage test .7
6.6 Decontamination .9
6.7 Leakage identification .9
7 Recommended test timeline .10
7.1 General .10
7.2 Design verification test .10
7.3 Factory test .10
7.4 In situ test .10
7.5 Evaluation of the test results .10
8 Marking . .11
Annex A (normative) Air tightness test method .12
Annex B (normative) Method for aerosol concentration uniformity test .15
Annex C (informative) Method and examples for CHEFU decontamination methodology
verification . 17
Bibliography .21

iii
ISO/FDIS 5371:2025(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 142, Cleaning equipment for air and other gases.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/FDIS 5371:2025(en)
Introduction
In laboratories and facilities dealing with critical or hazardous biological materials, such as biosafety
laboratories, vaccine manufacturing facilities and animal laboratory facilities, the removal of airborne bio-
aerosols in the facilities that are released to the surrounding environment is always a major concern. In
general, containment high efficiency filtration units (CHEFU) are used for such purpose. When installed in
the terminal outlet within the room, the required maintenance such as the decontamination and replacement
of filters, are performed in the containment room, e.g. the high-level biosafety lab. When installed in the
ventilation duct, all maintenance activities can be performed in the low-risk servicing area and a special
design for in situ decontamination or containment filter replacement measures needs to be put in place. This
document provides suppliers and users with basic performance requirements and test methods to validate
the performance of the devices.

v
FINAL DRAFT International Standard ISO/FDIS 5371:2025(en)
Containment high efficiency filtration unit (CHEFU) in
ventilation system of biosafety facilities
1 Scope
This document provides basic performance requirements and corresponding test methods for containment
high efficiency filtration units (CHEFUs). This document is applicable to the devices used to remove harmful
bio-aerosol in biosafety facilities and similar controlled environment. This document is not applicable to a
filtration unit for removing radioactive aerosol.
2 Normative references
The following documents are r
...

ISO/FDIS 5371
2025-03-06
ISO/FDIS 5371:2025(en)
ISO/TC 142
Secretariat: UNI
Date: 2025-04-14
Containment high efficiency filtration unit (CHEFU) in ventilation
system of biosafety facilities
Unités de filtration à très haute efficacité de confinement (CHEFU) dans le système de ventilation des
installations de biosécurité
FDIS stage
ISO/DISFDIS 5371:2025(en)
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
EmailE-mail: copyright@iso.org
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii
ISO/FDIS 5371:2025(en)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Design and construction . 3
5 Requirements . 3
5.1 Appearance . 3
5.2 Resistance to air flow . 3
5.3 Vacuum deformation test . 4
5.4 Air tightness . 4
5.5 Leakage test of the installed HEPA filter . 4
5.6 Decontamination. 4
5.7 Leakage identification . 4
6 Test methods . 5
6.1 Appearance . 5
6.2 Resistance to air flow . 5
6.3 Vacuum deformation test . 5
6.4 Air tightness . 6
6.5 Leakage test of the installed HEPA filter . 6
6.6 Decontamination. 9
6.7 Leakage identification . 10
7 Recommended test timeline . 10
7.1 General. 10
7.2 Design verification test . 10
7.3 Factory test . 11
7.4 In situ test . 11
7.5 Evaluation of the test results . 11
8 Marking . 12
Annex A (normative) Air tightness test method . 13
Annex B (normative) Method for aerosol concentration uniformity test . 17
Annex C (informative) Method and examples for CHEFU decontamination methodology
verification . 21
Bibliography . 26

MUST BEMUST BE USED USED
FOR FINAL FOR FINAL
iii
ISO/DISFDIS 5371:2025(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 142, Cleaning equipment for air and other gases.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
ISO/FDIS 5371:2025(en)
Introduction
In laboratories and facilities dealing with critical or hazardous biological materials, such as biosafety
laboratories, vaccine manufacturing facilities and animal laboratory facilities, the removal of airborne bio-
aerosols in the facilities that are released to the surrounding environment is always a major concern. In
general, containment high efficiency filtration units (CHEFU) are used for such purpose. When installed in the
terminal outlet within the room, the required maintenance such as the decontamination and replacement of
filters, are performed in the containment room, e.g. the high-level biosafety lab. When installed in the
ventilation duct, all maintenance activities can be performed in the low-risk servicing area and a special design
for in situ decontamination or containment filter replacement measures needs to be put in place. This
document provides suppliers and users with basic performance requirements and test methods to validate
the performance of the devices.
MUST BEMUST BE USED USED
FOR FINAL FOR FINAL
v
ISO/FDIS 5371:2025(en)
Containment high efficiency filtration unit (CHEFU) in ventilation
system of biosafety facilities
1 Scope
This document provides basic performance requirements and corresponding test methods for containment
high efficiency filtration units (CHEFUs). This document is applicable to the devices used to remove harmful
bio-aerosol in biosafety facilities and similar controlled environment. This document is not applicable to a
filtration unit for removing radioactive aerosol.
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 9626, Stainless steel needle tubing for the manufacture of medical devices — Requirements and test methods
ISO 14644--3, Cleanrooms and associated controlled environments — Part 3: Test methods
ISO 21501--1, Determination of particle size distribution — Single particle light interaction methods — Part 1:
Light scattering aerosol spectrometer
ISO 21501--4, Determination of particle size distribution — Single particle light interaction methods — Part 4:
Light scattering airborne particle counter for clean spaces
ISO 29463--1, High Efficiency Filtersefficiency filters and Filter Mediafilter media for Removing Particles from
Airremoving particles in air — Part 1: Classification, performance, testing and marking
ISO 29463-2, High Efficiency Filters-efficiency filters and Filter Mediafilter media for Removing Particles from
Airremoving particles in air — Part 2: Aerosol production, measuring equipment and particle-counting statistics
ISO 29463-3, High Efficiency Filters-efficiency filters and Filter Mediafilter media for Removing Particles from
Airremoving particles in air — Part 3: Testing flat sheet filter media
ISO 29463-4, High Efficiency Filters-efficiency filters and Filter Mediafilter media for Removing Particles from
Airremoving particles in air — Part 4: Test method for determining leakage of filter elements-Scan method
ISO 29463--5, High-efficiency filters and filter media for removing particles in air — Part 5: Test method for filter
elements
ISO 29464: 2024, Cleaning of 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, ISO 29463-
3, ISO 29463-,-4, ISO 29463-5 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
MUST BEMUST BE USED USED
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
FOR FINAL FOR FINAL
ISO/DISFDIS 5371:2025(en)
3.1 3.1
containment high efficiency filtration unit
CHEFU
filtration unit used in specific biological risk environment to remove harmful bio-aerosol from the air
3.2 3.2
aerosol
solid and/or liquid particles suspended in a gas
Note 1 to entry: Based on European Union and US Environmental Protection Agency information, atmospheric aerosol is
divided into four size categories: the ultrafine range x < 0,1 µm, the fine range 0,1 µm ≤ ≤ x ≤ ≤ 2,5 µm, the coarse range
2,5 µm < x ≤ 10 µm, and the large coarse range x > 10 µm, whereby x is the aerodynamic diameter of the particle.
[SOURCE: ISO 29464: 2024, 3.2.1]
3.3 3.3
bioaerosol
particles of biological origin suspended in a gaseous medium
Note 1 to entry: Bioaerosol particles include viruses, bacteria, fungi, pollen, plant debris, fragments of these and their
derivatives such as endotoxins, glucans, allergens and mycotoxin.
Note 2 to entry: The size of a bioaerosol particle can be larger if it is encased within a liquid drop, for example a virus in
sputum.
[SOURCE: ISO 29464: 2024, 3.2.20]
3.4 3.4
high efficiency particulate air filter
HEPA filter
filter with performance complying with requirements of filter classes ISO 35 H to ISO 45 H as specified in
ISO 29463-1
[SOURCE: ISO 29464: 2024, 3.2.66]
3.5 3.5
rated air flow rate
flow rate through a test device, either as stated by the manufacturer for defined conditions of use or as agreed
between the interes
...