ISO 22241-1

FINAL DRAFT
International
Standard
ISO/FDIS 22241-1
ISO/TC 22/SC 34
Diesel engines — NOx reduction
Secretariat: JISC
agent AUS 32 —
Voting begins on:
2026-07-29
Part 1:
Quality requirements
Voting terminates on:
2026-09-23
Moteurs diesel — Agent AUS 32 de réduction des NOx —
Partie 1: Exigences de qualité
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
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AND TO PROVIDE SUPPOR TING DOCUMENTATION.
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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 22241-1:2026(en) © ISO 2026

FINAL DRAFT
ISO/FDIS 22241-1:2026(en)
International
Standard
ISO/FDIS 22241-1
ISO/TC 22/SC 34
Diesel engines — NOx reduction
Secretariat: JISC
agent AUS 32 —
Voting begins on:
Part 1:
Quality requirements
Voting terminates on:
Moteurs diesel — Agent AUS 32 de réduction des NOx —
Partie 1: Exigences de qualité
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 2026
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.
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Published in Switzerland Reference number
ISO/FDIS 22241-1:2026(en) © ISO 2026

ii
ISO/FDIS 22241-1:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Designation . 2
5 Requirements and testing . 2
6 Handling, transportation and storage. 3
7 Marking . . 3
Annex A (informative) Chemical characteristics . 4
Annex B (informative) Precision of test methods . 5
Bibliography . 6

iii
ISO/FDIS 22241-1:2026(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 documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention drawn 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 on 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 22, Road vehicles, Subcommittee SC 34,
Propulsion, powertrain and powertrain fluids.
This third edition cancels and replaces the second edition (ISO 22241-1:2019), which has been technically
revised. It also incorporates the Amendment ISO 22241-1:2019/Amd 1:2019.
The main changes are as follows:
— incorporation of the ISO 22241-1:2019/Amd 1:2019 and editorial updates;
— alternative test method for biuret in Table 1 announced.
A list of all parts in the ISO 22241 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.

iv
ISO/FDIS 22241-1:2026(en)
Introduction
In order to protect the environment, keeping the air quality as clean as possible, exhaust emissions
regulations around the world have been strengthened considerably. In motor vehicles with diesel engines,
particulate matters (PM) and nitrogen oxide (NOx) emissions are the main concern, and efforts have
been focused on the development of technology which can reduce them effectively with minimum fuel
economy penalty. Selective catalytic reduction (SCR) converters using aqueous urea solution (AUS 32)
as the reduction agent are considered to be a key technology for reducing NOx emissions. The quality of
the urea solution used for that technology needs to be specified to ensure reliable and stable operation of
[1]
the SCR converter systems. ISO 22241 (all parts) provides the specifications for quality characteristics,
handling, transportation and storage, and refilling interface. It also outlines the test methods needed by the
manufacturers of motor vehicles and their engines, converter manufacturers, producers and distributors of
the urea solution, as well as fleet operators.
The aqueous urea solution (AUS 32), as specified in this document, is commercially available and may exist
1)
under various trade names, as for example AdBlue®, ARLA 32 .
1) Trade names of products AdBlue®, ARLA 32, DEF, etc., are examples of suitable products available commercially. This
information is given for the convenience of users of this document and does not constitute an endorsement by ISO of the
products named.
v
FINAL DRAFT International Standard ISO/FDIS 22241-1:2026(en)
Diesel engines — NOx reduction agent AUS 32 —
Part 1:
Quality requirements
1 Scope
This document specifies the quality characteristics of the nitrogen oxide (NOx) reduction agent aqueous
urea solution (AUS 32), which is needed to operate selective catalytic reduction (SCR) converter systems in
motor vehicles with diesel engines. SCR converter systems are particularly suitable for selectively reduci
...