ISO 4226

• Abstract:

  ISO 4226:2008 lays down the units to be used when reporting results of air quality measurements.

• Status: Not Published
• ICS: 01.060 - Quantities and units
• ICS: 13.040.01 - Air quality in general
• Technical Committee: ISO/TC 146/SC 4 - General aspects
• Drafting Committee: ISO/TC 146/SC 4 - General aspects
• Current Stage: 6000 - International Standard under publication
• Start Date: 18-Aug-2026
• Completion Date: 22-Aug-2026
• Ref Project: kSIST ISO/FDIS 4226:2026 - Air quality - General aspects - Quantities and associated units for reporting results of air quality measurements

• Revises: ISO 4226:2007 - Air quality — General aspects — Units of measurement
• Effective Date: 28-Oct-2023

Overview

ISO 4226:2026 – Air quality - General aspects - Quantities and associated units for reporting results of air quality measurements is an internationally recognized standard developed by ISO/TC 146. It specifies the recommended terms, symbols, and units to be used when reporting the results of air quality assessments. The use of standardized measurements is fundamental for ensuring consistency, clarity, and comparability across air quality monitoring, research, and regulatory activities worldwide.

By outlining agreed-upon quantities and associated units, ISO 4226 facilitates coherent communication and reporting of air quality data, helping organizations and authorities make informed decisions regarding air pollution control, environmental health, and workplace safety.

Key Topics

• Standardized Units: Specifies the use of SI (International System of Units)-based measurements for air quality results, including mass, volume, temperature, pressure, and concentration.
• Symbols and Terms: Recommends specific symbols and terms for a range of measurement quantities such as mass (m, g), temperature (T, K, °C), pressure (p, Pa), mass concentration (cm, g/m³), and more.
• Application-Specific Quantities: Defines suitable units for different contexts, including stationary source emissions, workplace atmospheres, ambient air, meteorology, and indoor air quality.
• Prefixes: Encourages the use of decimal prefixes (such as kilo (k), milli (m), micro (μ)) to express measurements conveniently and avoid large or small numerical values.
• Clarity and Consistency: Provides guidance on avoiding ambiguous symbols and the use of indices for distinction. Advises on the proper handling of dimensionless units and discourages the use of language-specific terms like “ppm” without clear explanation.
• Measurement Uncertainty: Details statistical quantities relevant to expressing measurement uncertainty, standard deviation, sample size, confidence levels, and coverage factors in air quality reporting.

Applications

ISO 4226 is crucial in diverse practical settings, including:

• Environmental Monitoring: Ensures consistent reporting of air pollution levels by governmental agencies tracking ambient air quality.
• Workplace Air Assessment: Standardizes units when evaluating exposure to airborne contaminants in occupational environments, critical for health and safety regulations.
• Industrial Emission Reporting: Facilitates clear communication of emissions data from stationary sources, supporting regulatory compliance and pollution abatement initiatives.
• Indoor Air Quality Studies: Provides a common reference for measurements in homes, offices, and public spaces, informing ventilation and air purification strategies.
• Scientific Research: Enables comparability in studies measuring gases, particulates, and other atmospheric parameters, promoting harmonized data analysis and sharing.
• Meteorological Reporting: Supports meteorologists by defining units for parameters such as humidity, wind speed, irradiance, and altitude, important for air quality modeling.

Related Standards

• ISO 80000 Series: Offers comprehensive guidance on quantities and units, serving as a reference for SI units across scientific disciplines, including those specified in ISO 4226.
• Other ISO Air Quality Standards: ISO/TC 146 develops related standards covering specific measurement methods for gases, particles, and vapors, complementing the foundational guidance in ISO 4226.
• IEC Electropedia & ISO Online Browsing Platform: Authoritative sources for terminology and further standardization documentation.

ISO 4226’s structured approach to air quality measurement reporting supports international harmonization, accurate data interpretation, and effective environmental management. Adhering to this standard enhances the quality and reliability of air quality information used by policymakers, scientists, and industry professionals worldwide.

SLOVENSKI STANDARD
oSIST ISO/DIS 4226:2026
01-junij-2026
Kakovost zraka - Splošni vidiki - Merske enote
Air quality - General aspects - Units of measurement
Qualité de l'air - Aspects généraux - Unités de mesurage
Ta slovenski standard je istoveten z: ISO/DIS 4226
ICS:
01.060 Veličine in enote Quantities and units
13.040.01 Kakovost zraka na splošno Air quality in general
oSIST ISO/DIS 4226:2026 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST ISO/DIS 4226:2026
oSIST ISO/DIS 4226:2026
DRAFT
International
Standard
ISO/DIS 4226
ISO/TC 146/SC 4
Air quality — General aspects —
Secretariat: DIN
Units of measurement
Voting begins on:
ICS: 01.060; 13.040.01
2025-11-24
Voting terminates on:
2026-02-16
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
This document is circulated as received from the committee secretariat.
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
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 SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 4226:2025(en)
oSIST ISO/DIS 4226:2026
DRAFT
ISO/DIS 4226:2025(en)
International
Standard
ISO/DIS 4226
ISO/TC 146/SC 4
Air quality — General aspects —
Secretariat: DIN
Units of measurement
Voting begins on:
ICS: 01.060; 13.040.01
Voting terminates on:
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
This document is circulated as received from the committee secretariat. BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 4226:2025(en)
ii
oSIST ISO/DIS 4226:2026
ISO/DIS 4226:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Quantities and associated units . 1
4.1 General .1
4.2 Use of quantities and units .1
4.3 Use of prefixes .2

iii
oSIST ISO/DIS 4226:2026
ISO/DIS 4226:2025(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 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).
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. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received (see www.iso.org/patents).
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 146, Air quality, Subcommittee SC 4, General
aspects.
This fourth edition cancels and replaces the third edition (ISO 4226:2007), which has been technically
revised.
The main changes are as follows:
— Clause 3 (Terms and definitions) has been added
— Information regarding use of quantities, units, and prefixes has been added to Clause 4
— Table 1 has been reorganized, and symbols for quantities have been added
— Table 2, Prefixes, has been added.
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
oSIST ISO/DIS 4226:2026
ISO/DIS 4226:2025(en)
Introduction
The series of International Standards on air quality includes the standardization of methods for the
measurement of gases, vapours and particles. In order to enable results to be compared either within or
between countries, it is essential to use agreed symbols and units of quantities for reporting of results of
measurements and oth
...

FINAL DRAFT
International
Standard
ISO/FDIS 4226
ISO/TC 146/SC 4
Air quality — General aspects —
Secretariat: DIN
Quantities and associated units
Voting begins on:
for reporting results of air quality
2026-06-22
measurements
Voting terminates on:
2026-08-17
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 4226:2026(en) © ISO 2026

FINAL DRAFT
ISO/FDIS 4226:2026(en)
International
Standard
ISO/FDIS 4226
ISO/TC 146/SC 4
Air quality — General aspects —
Secretariat: DIN
Quantities and associated units
Voting begins on:
for reporting results of air quality
measurements
Voting terminates on:
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.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 4226:2026(en) © ISO 2026

ii
ISO/FDIS 4226:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Quantities and associated units . 1
4.1 General .1
4.2 Use of quantities and units .1
4.3 Use of prefixes .2

iii
ISO/FDIS 4226:2026(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 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 146, Air quality, Subcommittee SC 4, General
aspects.
This fourth edition cancels and replaces the third edition (ISO 4226:2007), which has been technically
revised.
The main changes are as follows:
— Clause 3 has been added;
— information regarding the use of quantities, units and prefixes has been added to Clause 4;
— Table 1 has been reorganized and symbols for quantities have been added;
— Table 2 on prefixes has been added.
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 4226:2026(en)
Introduction
The International Standards on the general aspects of air quality include the standardization of methods for
the measurement of gases, vapours and particles. In order to enable results to be compared either within or
between countries, it is reasonable to use only a minimal number of symbols and units that have been agreed
upon to report the results of measurements and other relevant information so that sound conclusions can be
drawn.
v
...

ISO/DISFDIS 4226:2026(en)
ISO/TC 146/SC 4/WG 1 N 104
Secretariat: DIN
Date: 2026-04-2106-08
Air quality — General aspects — Quantities and associated units for
reporting results of air quality measurements
Qualité de l'air — Aspects généraux — Quantités et unités associées pour la communication des résultats des
mesures de la qualité de l'air
FDIS stage
ISO/FDIS 4226:2026(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: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO/FDIS 4226:2026(en)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Quantities and associated units . 1
4.1 General . 1
4.2 Use of quantities and units . 1
4.3 Use of prefixes . 2

iii
ISO/FDIS 4226:2026(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 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 146, Air quality, Subcommittee SC 4, General
aspects.
This fourth edition cancels and replaces the third edition (ISO 4226:2007), which has been technically revised.
The main changes are as follows:
— Clause 3— Clause 3 has been added;
— — Informationinformation regarding the use of quantities, units and prefixes has been added to
Clause 4Clause 4;;
— Table 1— Table 1 has been reorganized and symbols for quantities have been added;
— Table 2— Table 2 on prefixes has been added.
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.
Field Code Changed
iv
ISO/FDIS 4226:2026(en)
Introduction
The International Standards on the general aspects of air quality developed by ISO TC 146 include the
standardization of methods for the measurement of gases, vapours and particles. In order to enable results to
be compared either within or between countries, it is reasonable to use only a minimal number of symbols
and units that have been agreed upon to report the results of measurements and other relevant information
so that sound conclusions can be drawn.
v
ISO/FDIS 4226:2026(en)
Air quality — General aspects — Quantities and associated units for
reporting results of air quality measurements
1 Scope
This document establishes the terms and symbols used to report the results of air quality measurements.
NOTE General guidance on the International System of Units is given in the ISO 80000 series.
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 80000 (all parts), Quantities and units
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databased 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
4 Quantities and associated units
4.1 General
The namesterms and symbols for both the quantities and associated units specified in Tab
...