ISO 25081:2026

Nonwovens — Test methods for filtration of particulate matter

This document specifies a method to test filtration performance of particulate matter of nonwovens. This document is applicable to nonwovens for air filtration.

Nontissés — Méthodes d'essai de filtration de matière particulaire

General Information

• Status: Published
• Publication Date: 18-May-2026
• ICS: 59.080.30 - Textile fabrics
• Technical Committee: ISO/TC 38 - Textiles
• Drafting Committee: ISO/TC 38/WG 9 - Nonwovens
• Current Stage: 6060 - International Standard published
• Start Date: 19-May-2026
• Due Date: 15-Apr-2027
• Completion Date: 19-May-2026

Overview

ISO 25081:2026 – Nonwovens - Test Methods for Filtration of Particulate Matter is an international standard developed by ISO for the evaluation of nonwoven materials used in air filtration. This standard establishes a harmonized methodology for measuring the filtration performance of nonwovens when capturing particulate matter. It addresses inconsistencies in national and regional test methods, offering uniform criteria for laboratory testing, ensuring reliability, and supporting technical exchange in the filtration industry.

The standard applies to nonwovens intended for air filtration applications, such as face masks, air purifiers, and industrial filtration systems. It covers procedures for sample preparation, apparatus requirements, test conditions, and calculation of key filtration performance metrics.

Key Topics

ISO 25081:2026 specifies several critical areas:

• Filtration Efficiency: Provides definitions and procedures for measuring both initial and load filtration efficiency, representing a material’s ability to remove particulate matter under various conditions.
• Aerosol Generation and Sampling: Outlines requirements for generating test aerosols (solid and liquid phase) using substances such as sodium chloride (NaCl) and oils (DEHS, DOP).
• Test Apparatus: Details essential equipment including filter testers, photometers, flow meters, pressure gauges, and specimen clamps, with specifications for accuracy and calibration.
• Sample Preparation and Pretreatment: Describes mandatory pretreatment steps (temperature, humidity, washing) and sampling criteria to ensure valid and reproducible results.
• Test Conditions and Procedures: Sets required environmental parameters (temperature and humidity), specifies airflow rates, and describes the step-by-step testing process.
• Results Calculation and Reporting: Provides guidance on calculating filtration efficiency, airflow resistance, filter time, and dust-hold capacity, as well as detailed reporting requirements.
• Terminology: Establishes definitions for key terms such as aerosol, particulate matter, filtration efficiency, airflow rate, and dust-hold capacity, ensuring consistent communication.

Applications

The practical value of ISO 25081:2026 is its ability to standardize the assessment of nonwoven filtration materials in a diverse range of air filtration products, including:

• Personal Protective Equipment (PPE): Critical for manufacturers of face masks and respirators, where consistent particulate filtration performance is essential for user safety.
• HVAC Systems and Air Purifiers: Supports the reliable assessment of commercial and residential air filters, ensuring product quality and regulatory compliance.
• Industrial Dust Collection: Enables manufacturers of industrial filtration products to benchmark material performance under controlled and repeatable conditions.
• Research and Development: Provides a baseline for R&D teams to compare new nonwoven materials and optimize product formulations for enhanced filtration efficiency.
• Quality Control and Certification: Assists testing laboratories and certifying bodies in verifying compliance with performance specifications, facilitating global trade and procurement.
• Technical Exchange: Promotes technical harmonization across borders, reducing barriers to international trade and fostering innovation in filtration technology.

Related Standards

ISO 25081:2026 references and aligns with several key international standards for terminology, testing conditions, and material preparation:

• ISO 139 – Textiles: Standard atmospheres for conditioning and testing
• ISO 3696 – Water for analytical laboratory use: Specification and test methods
• ISO 6330 – Domestic washing and drying procedures for textile testing
• ISO 29464 – Cleaning of air and other gases: Vocabulary
• ISO 15900 – Determination of particle size distribution: Differential electrical mobility analysis for aerosol particles
• ISO 16972 – Respiratory protective devices: Vocabulary and graphical symbols

These related standards ensure that ISO 25081:2026 is embedded within the broader framework of recognized practices in filtration and textile testing.

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Keywords: ISO 25081, nonwovens, particulate filtration, air filtration test, filtration efficiency, nonwoven test methods, air filter standards, PPE testing, ISO air filtration, textile standards, particulate matter filtration, laboratory test methods, aerosol filtration, industrial filtration testing.

Standards Content (Sample)

International
Standard
ISO 25081
First edition
Nonwovens — Test methods for
2026-05
filtration of particulate matter
Nontissés — Méthodes d'essai de filtration de matière
particulaire
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 Principle . 2
5 Apparatus . 3
5.1 Filter tester .3
5.1.1 General .3
5.1.2 Aerosol generating system .3
5.1.3 Test system .3
5.2 Balance .4
5.3 Timer .4
6 Materials and reagents . 5
7 sample preparation . 6
7.1 General .6
7.2 Temperature and humidity pretreatment .6
7.3 Washing pretreatment .6
7.4 Sampling requirements .6
7.4.1 Sampling .6
7.4.2 Number of test specimens . . .6
8 Test conditions . 7
9 Test procedure . 7
9.1 Apparatus preparation .7
9.2 Set the airflow rate .7
9.3 Start the test .7
10 Calculation and expression of results . 8
10.1 Filtration efficiency .8
10.2 Initial airflow resistance .8
10.3 Filter time .8
10.4 Final airflow resistance .8
10.5 Dust-hold capacity .8
11 Test report . 8
Bibliography .10

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
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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).
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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
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This document was prepared by Technical Committee ISO/TC 38 Textiles.
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
Nonwovens are important raw materials for protective products, such as masks and air purifiers. The
performance of nonwovens has a significant impact on the quality of protective products. Among them, the
particulate matter filtration performance is the core indicator for evaluating the performance of nonwovens.
However, there is currently no independent filtration performance test method standard to uniformly
regulate the definition of terms, instrument equipment, test parameters, test procedures and result
calculation. Different countries and regions adopt different detection methods, which is not conducive
to technical comparison and exchange, and also has a certain impact on the detection and technological
development of nonwovens filtration performance. It is necessary to establish a separate method standard
for testing the filtration performance of nonwovens.

v
International Standard ISO 25081:2026(en)
Nonwovens — Test methods for filtration of particulate
matter
1 Scope
This document specifies a method to test filtration performance of particulate matter of nonwovens. This
document is applicable to nonwovens for air filtration.
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 139, Textiles — Standard atmospheres for conditioning and testing
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 6330, Textiles — Domestic washing and drying procedures for textile testing
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
aerosol
suspension of solid and/or liquid particulate matter in a gas
[SOURCE: ISO 29464:2024, 3.2.1, modified— without Note 1]
3.2
liquid phase aerosol
liquid particles suspended in a gas
[SOURCE: ISO 29464:2024, 3.2.2]
3.3
solid phase aerosol
solid particles suspended in a gas
[SOURCE: ISO 29464:2024, 3.2.9]
3.4
particulate matter
PM
solid and/or liquid particles
[SOURCE: ISO 29464:2024, 3.2.123]

3.5
count median diameter
CMD
particle size of a particle distribution for which one-half the total number of particles are larger and one-half
are smaller
[SOURCE: ISO 16972:2020, 3.61]
3.6
filtration efficiency
ratio of the difference between the concentration of particulate matter before and after nonwoven filtration
and the concentration of particulate matter before nonwoven filtration
3.7
initial filtration efficiency
filtration efficiency of the nonwoven which is calculated as soon as possible after the start of test
3.8
load filtration efficiency
lowest value of filtration efficiency of the nonwoven in the process of filtration from clean state to when the
filtration of nonwoven reaches a certain dust-hold capacity or a certain airflow resistance
3.9
airflow rate
volume of air flowing through the nonwoven per unit time
3.10
airflow resistance
static pressure difference before and after nonwoven filtration
3.11
initial airflow resistance
static pressure difference of the nonwoven which is calculated as soon as possible after the start of test
3.12
final airflow resistance
static pressure difference of the nonwoven which needs to be replaced or regenerated after filtration
3.13
dust-hold capacity
quality of particula
...