ISO 4226:2026

• Abstract:

  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.

• Status: Published
• Publication Date: 14-Sep-2026
• 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: 6060 - International Standard published
• Start Date: 15-Sep-2026
• Due Date: 25-Sep-2026
• Completion Date: 15-Sep-2026
• Ref Project: SIST ISO 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

ISO 4226:2026 is an International Standard from ISO for reporting results of air quality measurements. It specifies the terms, symbols, quantities and associated units to use, so measurement reports can be written in a consistent way and compared within and between countries.

What does ISO 4226:2026 specify?

ISO 4226:2026 specifies the notation used when reporting air quality measurement results. It is organized into four clauses - Scope, Normative references, Terms and definitions, and Quantities and associated units - and supported by Table 1 and Table 2.

Clause 4 groups the reporting quantities by field of use. It covers general quantities, stationary source emissions, workplace atmospheres, ambient air quality, meteorology, indoor air, statistical quantities linked to measurement uncertainty, and other statistical quantities. That structure matters in practice because the right symbol or unit can depend on whether the result comes from an emission test, an indoor survey, or an ambient monitoring program.

What are the key requirements of ISO 4226:2026?

ISO 4226:2026 focuses on consistent reporting, not on how to make the measurements. The main requirement is to use the terms and symbols listed in Table 1 when reporting air quality results, and to keep other quantities and units in line with ISO 80000.

Use the listed quantities and units

Clause 4.1 says the terms and symbols in Table 1 should be used for reporting results of air quality measurements. Table 1 covers quantities such as mass, temperature, pressure, concentration, fractions, flowrate, density, humidity, wind velocity, air change rate, uncertainty terms, and detection limits. In practice, this gives report authors a common language and reduces confusion when results move between laboratories, clients, and regulators.

Apply the right quantity for the application area

Clause 4.2 separates the reporting quantities by area of use. It identifies general quantities, then specific quantities for stationary source emissions, workplace atmospheres, ambient air quality, meteorology, indoor air, and statistical treatment of data. This matters because the same measurement campaign can involve different types of results, and the document ties each type to an appropriate quantity and unit.

Report uncertainty in a controlled way

Clause 4.2 states that measurement uncertainty shall always be expressed in the unit of the measurand, and that relative measurement uncertainty is usually given as a percentage of the measured value. For users, that means uncertainty should match the reported quantity instead of being written in a separate or incompatible unit.

Distinguish identical symbols by unit or index

Clause 4.2 notes that some different quantities share the same symbol. ISO 4226:2026 relies on the unit, or on a suitable index, to avoid ambiguity. In practice, that helps readers tell whether a symbol refers to, for example, mass concentration or volume concentration, without changing the broader notation system.

Avoid confusing language-specific units

Clause 4.2 allows dimensionless quantities such as fractions or sample size, and it warns that language-specific units like ppm or ppb can cause confusion. If such units are used, the report has to explain what they mean. That is important for international exchange of data, where local shorthand may not be understood the same way everywhere.

Use prefixes when they improve readability

Clause 4.3 allows decimal multiples and submultiples of units, and Table 2 lists typical prefixes used in air quality measurements. This helps avoid awkward very large or very small numbers and makes results easier to read and compare. The clause also explains that a prefix is attached directly to a single unit symbol to form a new unit symbol.

Who uses ISO 4226:2026?

ISO 4226:2026 is used by people who report, review, compare or specify air quality measurement results. Typical users include environmental laboratories, air monitoring organizations, workplace hygiene teams, emissions testing teams, indoor air assessors, meteorological services, regulators and technical writers.

In practice, they use it to choose the correct symbol, unit, prefix and uncertainty expression for reports, data sheets, monitoring summaries and technical documents. It is especially useful when the same reporting system has to work across gases, vapours and particles in different measurement settings.

What changed in ISO 4226:2026 from the previous edition?

ISO 4226:2026 replaces ISO 4226:2007 and is technically revised. The stated changes are:

• Clause 3 has been added.
• Clause 4 now includes more information on the use of quantities, units and prefixes.
• Table 1 has been reorganized and symbols for quantities have been added.
• Table 2 on prefixes has been added.

Which standards are used with ISO 4226:2026?

ISO 80000 (all parts), Quantities and units, is the normative reference in ISO 4226:2026. It provides the general principles for units and quantities that apply whenever ISO 4226:2026 refers beyond its own tables. The note in the Scope also points readers to the ISO 80000 series for general guidance on the International System of Units.

What does the ISO 4226:2026 document contain?

ISO 4226:2026 contains a structured list of quantities and associated units for air quality reporting, plus a table of prefixes for decimal multiples and submultiples. Table 1 organizes the material by application area, including general use, emissions, workplace atmospheres, ambient air, meteorology, indoor air, statistics and other quantities.

The document also explains how to use the symbols, when to use prefixes, how to handle repeated symbols, and how to express measurement uncertainty and dimensionless results. In practice, it is a reporting and notation reference for designing forms, writing test reports, checking data consistency and standardizing technical communication.

SLOVENSKI STANDARD
01-oktober-2026
Nadomešča:
SIST ISO 4226:2013
Kakovost zraka - Splošni vidiki - Veličine in enote za poročanje o rezultatih
meritev kakovosti zraka
Air quality - General aspects - Quantities and associated units for reporting results of air
quality measurements
Qualité de l'air - Aspects généraux - Grandeurs et unités associées pour consigner les
résultats des mesurages de la qualité de l'air
Ta slovenski standard je istoveten z: ISO 4226:2026
ICS:
01.060 Veličine in enote Quantities and units
13.040.01 Kakovost zraka na splošno Air quality in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

International
Standard
ISO 4226
Fourth edition
Air quality — General aspects —
2026-09
Quantities and associated units
for reporting results of air quality
measurements
Qualité de l'air — Aspects généraux — Grandeurs et unités
associées pour consigner les résultats des mesurages de la qualité
de l'air
Reference number
© ISO 2026
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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
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
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
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
International St
...

International
Standard
ISO 4226
Fourth edition
Air quality — General aspects —
2026-09
Quantities and associated units
for reporting results of air quality
measurements
Qualité de l'air — Aspects généraux — Grandeurs et unités
associées pour consigner les résultats des mesurages de la qualité
de l'air
Reference number
© ISO 2026
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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
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
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
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
International Standard ISO 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 unda
...