ISO 21025:2026

• Abstract:

  This document specifies the test method for evaluating the formaldehyde purification performance of interior wall coatings using the bag method. This document is applicable to the measurement and evaluation of formaldehyde purification performance of various types of interior wall coatings. This document can also apply to other indoor decoration materials with formaldehyde purification performance, such as wallpaper, carpets and decorative panels. Additionally, the method can be extended to the evaluation of the purification performance of other carbonyl compounds, such as acetaldehyde, propionaldehyde and butyraldehyde.

• Status: Published
• Publication Date: 02-Aug-2026
• ICS: 87.040 - Paints and varnishes
• Technical Committee: ISO/TC 35/SC 16 - Chemical analysis
• Drafting Committee: ISO/TC 35/SC 16 - Chemical analysis
• Current Stage: 6060 - International Standard published
• Start Date: 03-Aug-2026
• Due Date: 31-May-2026
• Completion Date: 03-Aug-2026

Overview

ISO 21025: Paints and Varnishes - Assessment of Formaldehyde Purification Effect of Interior Wall Coatings by Bag Method is an international standard published by ISO. It provides a rigorous methodology for evaluating the formaldehyde purification performance of interior wall coatings using the bag method. This standard is relevant for manufacturers, testing laboratories, and quality assurance professionals to ensure that wall coatings reduce formaldehyde levels, enhancing indoor air quality and supporting occupant health.

Key Topics

• Scope and Applicability:
  ISO 21025 applies to the measurement and evaluation of formaldehyde purification in a range of interior wall coatings. The method can also be adapted for other indoor materials such as wallpaper, carpets, and decorative panels.

• Bag Method Principle:
  The evaluation uses an inert, airtight sampling bag in which a prepared specimen panel is exposed to a controlled formaldehyde environment. The change in formaldehyde concentration is then measured over time.

• Key Definitions:

  • Natural reduction ratio: Compares the decrease in formaldehyde in a blank bag over time.
  • Initial and long-term purification efficiency: Quantifies the sample’s capability to purify formaldehyde after single and repeated exposures.

• Test Conditions & Procedures:

  • Use of analytical-grade reagents, defined substrate materials, and high-purity gases.
  • Standardized temperature (23 ± 2 °C) and humidity (50 ± 5 %) settings.
  • Triplicate determinations with required blank tests to ensure accuracy.

• Equipment and Materials:

  • Inert sampling bags, microinjectors, sampling and vacuum pumps, mass flow controllers, and standard substrates such as PVC.
  • Adherence to other ISO reference methods for sample preparation, analysis, and reporting.

Applications

• Product Certification:
  Ensures that wall coatings marketed as formaldehyde-reducing are tested and validated according to internationally recognized protocols.

• Building Materials Evaluation:
  Enables accurate comparison of the air purification performance of paints, varnishes, and other decorative products used in interior environments.

• Quality Assurance & Research:
  Provides a repeatable testing process for product development, regulatory compliance, and interlaboratory comparisons.

• Indoor Air Quality Improvement:
  Assists architects, builders, and facility managers in selecting materials that contribute to healthier building environments by minimizing formaldehyde exposure.

• Extension to Other Compounds:
  The bag method described may be applied to assess the purification effect on additional carbonyl compounds such as acetaldehyde, broadening its utility in indoor air quality assessments.

Related Standards

To ensure comprehensive testing and alignment with best practices, ISO 21025 refers to several key international documents:

• ISO 1513: Paints and varnishes - Examination and preparation of test samples
• ISO 3696: Water for analytical laboratory use - Specification and test methods
• ISO 5725-1 and ISO 5725-2: Accuracy (trueness and precision) of measurement methods and results
• ISO 15528: Paints, varnishes and raw materials for paints and varnishes - Sampling
• ISO 16000-3: Indoor air - Determination of formaldehyde and other carbonyl compounds in indoor air and test chamber air - Active sampling method

These references ensure robust precision, repeatability, and reproducibility of formaldehyde purification assessments, supporting both regulatory and market-driven requirements.

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By adhering to ISO 21025, stakeholders can reliably assess the formaldehyde purification effect of wall coatings, contributing to safer and healthier indoor environments and supporting claims of air purification performance in building materials.

International
Standard
ISO 21025
First edition
Paints and varnishes — Assessment
2026-08
of formaldehyde purification effect
of interior wall coatings by bag
method
Peintures et vernis — Évaluation de l’effet de purification du
formaldéhyde des revêtements muraux intérieurs par la méthode
du sac
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
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Reagents and materials . 2
7 Experimental system validation . 3
7.1 Test equipment .3
7.2 Cleaning of sampling bags .3
7.3 Measurement of natural reduction ratio of formaldehyde in sampling bag .4
8 Analysis of formaldehyde concentration . 4
9 Sampling . 4
10 Standard test conditions . 4
11 Test procedures . 4
11.1 General .4
11.2 Preparation and condition of specimen panel .5
11.3 Measurement of initial formaldehyde purification efficiency .5
11.4 Measurement of long-term formaldehyde purification efficiency .5
11.4.1 Specimen panel saturation test .5
11.4.2 Test on long-term formaldehyde purification efficiency .5
11.4.3 Determination of formaldehyde emission from specimen panel .6
12 Precision . 6
12.1 General .6
12.2 Repeatability limit, r . .6
12.3 Reproducibility limit, R .6
13 Test report . 6
Annex A (informative) Results of the interlaboratory test . 7
Bibliography . 9

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
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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
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ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
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rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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this may not represent the latest information, which may be obtained from the patent database available at
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Any trade name used in this document is information given for the convenience of users and does not
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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 35, Paints and varnishes.
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
International Standard ISO 21025:2026(en)
Paints and varnishes — Assessment of formaldehyde
purification effect of interior wall coatings by bag method
WARNING — The use of this document can involve hazardous materials, operations and equipment.
This document does not purport to address all of the safety problems associated with its use. It is
the responsibility of users of this document to take appropriate measures to ensure the safety and
health of personnel prior to the application of the document, and to determine the applicability of
any other restrictions for this purpose.
1 Scope
This document specifies the test method for evaluating the formaldehyde purification performance of
interior wall coatings using the bag method.
This document is applicable to the measurement and evaluation of formaldehyde purification performance
of various types of interior wall coatings.
This document can also apply to other indoor decoration materials with formaldehyde purification
performance, such as wallpaper, carpets and decorative panels. Additionally, the method can be extended
to the evaluation of the purification performance of other carbonyl compounds, such as acetaldehyde,
propionaldehyde and butyraldehyde.
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 1513, Paints and varnishes — Examination and preparation of test samples
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling
ISO 16000-3, Indoor air — Part 3: Determination of formaldehyde and other carbonyl compounds in indoor air
and test chamber air — Active sampling method
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
natural reduction ratio of formaldehyde in sampling bag
ratio of the reduced concentration of formaldehyde in the blank sampling bag to the initial concentration of
formaldehyde within a certain period of time

3.2
initial formaldehyde purification efficiency
ability of the coating test panel in the bag to purify formaldehyde after applying a single specified
concentration of formaldehyde, under the specified test conditions
3.3
long-term formaldehyde purification efficiency
ability of the coating test panel in the bag to maintain formaldehyde purification performance after repeated
application of formaldehyde at a specified concentration, under the specified test conditions
4 Principle
The specimen panel is prepared according to the theoretical application amount and application method
provided by the coatings product manufacturer.
Then the specimen panel is conditioned under standard test conditions for a specific period of time and put in
a sampling bag. A certain amount of formaldehyde solution is injected, or a certain amount of formaldehyde
solution is injected several times until certain saturation state has been reached.
The change of formaldehyde concentration in the bag within a specific period of time is analysed, and the
initial formaldehyde purification efficiency and long-term formaldehyde purification efficiency of the sample
are calculated.
5 Apparatus
5.1 Sampling bag, with the following characteristics:
— material and capacity: the sampling bag material shall be inert, impermeable, and non-sorbing [e.g.
fluorinated resins, such as poly (vinyl fluoride) (PVF) or fluoroethylene/fluoropropylene copolymer
(FEP) plastic]. The bag capacity shall be at least 50 l.
— airtightness: sampling bags shall be sealed securely with low-emitting tape or sealing strip or heat
bonded so as to be isolated from the uncontrolled ambient air.
— background concentration: the background concentration shall be as low as possible (e.g. below 7,5 µg/
m for formaldehyde) so that it does not interfere with the test results.
5.2 Micro syringe, with a volume of 10 μl and division value of 0,2 μl.
5.3 Sampling pump, which shall meet the requirements of ISO 16000-3. The flow shall be stable during
the sampling process. The flow range shall be 0 ml/min to 1 200 ml/min, and the flow fluctuation shall not
exceed ± 5 % of the sampling flow. Gas flow meters should be regularly used to calibrate the sampling pump.
5.4 Gas mass flow controller for filling the sampling bag with carrier gas. The response time should be
less than 100 ms and the repeatability should be ≤ 0,1 % (full scale). Gas flow meters should be regularly
used to calibrate gas mass flow controllers.
5.5 Vacuum pump, empty the gas in the sampling bag quickly.
...