ISO/FDIS 10121-1

• Abstract:

  ISO 10121-1:2014 aims to provide an objective laboratory test method, a suggested apparatus, normative test sections and normative tests for evaluation of three different solid gas-phase air cleaning media (GPACM) or GPACM configurations for use in gas-phase air cleaning devices intended for general filtration applications. ISO 10121-1:2014 is specifically intended for challenge testing and not for general material evaluation or pore system characterization. The three different types of GPACM identified in ISO 10121-1:2014 are GPACM-LF (particles of different shape and size intended for e.g. Loose Fill applications), GPACM-FL (FLat sheet fabric intended for e.g. flat one layer, pleated or bag type devices) and GPACM-TS (three dimensional structures that are many times thicker than flat sheet and e.g. used as finished elements in a device). The tests are conducted in an air stream and the GPACM configurations are challenged with test gases under steady-state conditions. Since elevated gas challenge concentrations (relative to general ventilation applications) are used, test data should be used to compare GPACM within the same configuration and not for the purpose of predicting performance in a real situation. It is also not implied that different GPACM configurations can be directly compared. The primary intention is to be able to compare like GPACM configurations to like, not between GPACM configurations. Testing of complete devices is described in ISO 10121‑2. To ensure objectivity for test equipment suppliers, no specific design of the test apparatus is defined: an example is illustrated in an annex. Instead normative demands for media sample holder design, apparatus properties and validation tests are specified.

• Status: Not Published
• ICS: 91.140.30 - Ventilation and air-conditioning systems
• Technical Committee: ISO/TC 142 - Cleaning equipment for air and other gases
• Drafting Committee: ISO/TC 142/WG 8 - Gas-phase air cleaning devices
• Current Stage: 5000 - FDIS registered for formal approval
• Start Date: 13-May-2026
• Completion Date: 28-Feb-2026

• Consolidates: prEN ISO 10121-1 - Test method for assessing the performance of gas-phase air cleaning media and devices for general ventilation - Part 1: Gas-phase air cleaning media (ISO/DIS 10121‑1:2025)
• Effective Date: 12-Feb-2026
• Revises: ISO 10121-1:2014 - Test method for assessing the performance of gas-phase air cleaning media and devices for general ventilation — Part 1: Gas-phase air cleaning media
• Effective Date: 28-Oct-2023

Overview

ISO/FDIS 10121-1:2026 specifies standardized laboratory test methods for evaluating the performance of gas-phase air cleaning media (GPACM) used in general ventilation applications. Developed by the International Organization for Standardization (ISO), this standard outlines objective procedures, required apparatus characteristics, and normative requirements for testing three common types of GPACM. This testing is crucial for ensuring reliable and comparable results among different media configurations, supporting both manufacturers and end-users in selecting and benchmarking gas-phase filtration products.

The document is not intended for whole device assessment or for predicting real-world performance due to the elevated gas challenge concentrations used during testing. Instead, ISO/FDIS 10121-1 enables direct comparison of the same type of GPACM under controlled laboratory conditions, improving communication between media suppliers, device manufacturers, and users.

Key Topics

• Objective Challenge Testing: The standard prescribes precise conditions where GPACM samples are exposed to test gases under steady-state conditions. Four key parameters are measured: pressure drop, capacity, removal efficiency, and retentivity.

• Types of GPACM Covered:

  • GPACM-LF: Loose fill media, composed of particles of various shapes and sizes for bulk fill applications.
  • GPACM-FL: Flat sheet media, typically used in pleated, single-layer, or bag-type filter devices.
  • GPACM-TS: Three-dimensional structured media, thicker than flat sheets and often utilized as finished elements within devices.

• Standardized Apparatus and Sample Holders: The standard provides normative requirements for GPACM sample holders and testing apparatus to eliminate test biases, increase repeatability, and ensure relevant data for the comparison of like configurations.

• Data Collection and Reporting: Comprehensive guidance is provided on test setup, sequence, validation of equipment, and reporting. The aim is to facilitate consistent interpretation and communication of test results.

• Scope Limitations: Not designed for general material evaluation, pore system characterization, or direct comparison between differing GPACM configurations. Testing of complete gas-phase air cleaning devices is addressed separately in ISO 10121-2.

Applications

ISO/FDIS 10121-1 is widely applicable in the air filtration industry, particularly for:

• Media Manufacturers: Enables accurate benchmarking and quality control of gas-phase air cleaning media intended for general ventilation systems.
• Device Producers: Assists in component selection by providing objective performance data for different media under standardized conditions.
• Laboratories & Test Facilities: Establishes required methods and apparatus for consistent assessment of filtration media.
• Quality Assurance & Procurement: Supports technical comparison and informed specification of GPACM products for residential, commercial, and industrial ventilation projects.

Use of the ISO/FDIS 10121-1 testing protocol helps ensure that only high-performing gas-phase air cleaning media are integrated into filtration devices, aligning with growing air quality requirements in residential, public, and workplace environments.

Related Standards

• ISO 10121-2: Test methods for assessing the performance of complete gas-phase air cleaning devices.
• ISO 10121-3: Classification system for GPACDs used in general ventilation for cleaning polluted outdoor air.
• ISO 29464: Definitions related to air filtration and related equipment.
• ASHRAE 145.1 & 145.2: US-based standards for laboratory assessment of gas-phase air cleaning devices and media.
• ASTM D2854-09: Standard method for determining apparent density of activated carbon, often referenced in filtration testing.
• JIS B 9901: Japanese standard relevant to gas-phase filtration.

By referencing ISO/FDIS 10121-1 alongside these related standards, organizations can ensure comprehensive and internationally recognized evaluation of gas-phase air cleaning media for ventilation systems.

For more detailed technical requirements and procedures, access the latest edition of ISO/FDIS 10121-1 from the ISO website or your national standards body.

FINAL DRAFT
International
Standard
ISO/TC 142
Test method for assessing the
Secretariat: UNI
performance of gas-phase air
Voting begins on:
cleaning media and devices for
2026-09-22
general ventilation —
Voting terminates on:
2026-11-17
Part 1:
Gas-phase air cleaning media
(GPACM)
Méthodes d'essai pour l'évaluation de la performance des médias
et des dispositifs de filtration moléculaire pour la ventilation
générale —
Partie 1: Médias de filtration moléculaire (GPACM)
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-
ISO/CEN PARALLEL PROCESSING 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
FINAL DRAFT
International
Standard
ISO/TC 142
Test method for assessing the
Secretariat: UNI
performance of gas-phase air
Voting begins on:
cleaning media and devices for
general ventilation —
Voting terminates on:
Part 1:
Gas-phase air cleaning media
(GPACM)
Méthodes d'essai pour l'évaluation de la performance des médias
et des dispositifs de filtration moléculaire pour la ventilation
générale —
Partie 1: Médias de filtration moléculaire (GPACM)
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
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ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 7
4.1 Symbols .7
4.2 Abbreviated terms .9
5 Testing of different GPACM configurations . 9
5.1 General .9
5.2 Test setup and normative GPACM sample holder .10
5.3 Raw data, sampling accuracy and normative generation parameters . 12
5.4 Test parameters for the standardized benchmark test . 13
5.4.1 General . 13
5.4.2 Challenge test concentration . 13
5.4.3 GPACMs for VOC tested with toluene . 13
5.4.4 GPACMs for acids and bases tested with SO and NH respectively .14
2 3
5.4.5 Retentivity test .14
5.5 Test parameters selected between user and supplier .14
5.5.1 General .14
5.5.2 Face velocity and material thickness .14
5.5.3 Challenge compound . . 15
5.5.4 Challenge concentration . 15
5.5.5 Temperature and relative humidity . 15
5.5.6 Test duration . 15
6 Test sequence .15
6.1 General . 15
6.2 Conditioning and pressure drop determination .16
6.2.1 General .16
6.2.2 Procedure .16
6.2.3 Calculations . .16
6.2.4 Reporting and graphs .16
6.3 Capacity determination .16
6.3.1 General .16
6.3.2 Procedure .17
6.3.3 Calculations . .17
6.3.4 Reporting and graphs .19
6.4 Retentivity determination . 20
6.4.1 General . 20
6.4.2 Procedure . 20
6.4.3 Calculations . . 20
6.4.4 Reporting and graphs .21
7 Validation of test setup.21
7.1 General .21
7.2 Determination of rise time and decay time .21
7.2.1 General .21
7.2.2 Procedure .21
7.2.3 Calculations . . 22
7.2.4 Reporting and graphs . 22
8 Evaluation and report .23
8.1 Test report introduction . 23
8.2 Test report example . 23

iii
Annex A (normative) Test equipment requirements, equipment validation and routine
operation .27
Annex B (informative) Challenge compounds, generation sources and analysis techniques .31
Annex C (informative) Design of a media test rig .36
Annex D (normative) Required sampling procedures and test parameters for different GPACM .37
Bibliography . 41

iv
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 142, Cleaning equipment for air and other gases,
in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC
195, Cleaning equipment for air and other gases, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 10121-1:2014), which has been technically
revised.
The main changes are as follows:
— terms and definitions have been updated to conform with ISO 29464:2024;
— test compounds have been reviewed in Annex B. Challenge concentration recommendations have been
removed for compounds requiring special attention, ozone concentration have been lowered, and all
other challenge concentrations conform with ISO 10121-2 and ISO 10121-3;
— 6.2.1, 6.3.1, 6.4.1, 6.3.3, 6.4.2, 7.2.2 have been reworded and clarified. In addition, challenge gas, species
or compound have been changed to compound unless a specific gas, e.g. SO , is discussed.
A list of all parts in the ISO 10121 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.

v
Introduction
There is an increasing use and need for gas-phase filtration in general filtration applications. This demand
can be expected to increase rapidly due to the increasing pollution problems in the world together with an
increasing awareness that solutions to the problems are available in the form of filtration devices or phrased
more technically: gas-phase air cleaning devices (GPACD). The performance of devices using adsorption for
gas removal relies to a large extent on the performance of a solid gas-phase air cleaning media (GPACM)
incorporated in the device. Still, applications, device performance and media performance are often poorly
understood by the user and supplier of such media and devices. Media tests can also be adequate to offer
data for real applications if actual low concentrations (<100 ppb) and longer exposure times (>weeks) can be
used in the test, provided that the geometrical configuration, packing density and air flow conditions of the
small-scale test specimen are equal to those used in the real applications. Such tests are however not included
in the scope of this document. This document attempts to increase understanding and communication by
supplying a more standardized interface between media suppliers, device suppliers and end users. Other
[1] [2]
standards exist for general ventilation (JIS B 9901), automotive filters by ISO 11155-2, in-duct sorptive
[2] [3]
media gas-phase air-cleaning devices (ASHRAE 145.2) and for adsorptive media (ASHRAE 145.1) and
[5]
ASTM E 300-3. The first edition of the ISO 10121 series was the first International Standard for general
gas phase filtration.
This document provides methods, test equipment, data interpretation and reporting for three different
types of gas-phase air cleaning media (GPACM) intended for use in gas-phase air cleaning devices (GPACDs)
for general ventilation applications.
In addition, information is given in the following annexes:
— Annex A describes the normative validation procedure in detail in a tabulated form;
— Annex B gives a list of possible test compounds, generation sources and suggests proper analysis
equipment for common test compounds;
— Annex C describes the design of the test rig except the normative sample holder;
— Annex D describes the normative test setup and normative section of the test rig for the three different
media configurations.
The ISO 10121 series consist of three parts.
— ISO 10121-1 (this document) covers three different media configurations and provides a standardized
interface between media suppliers and producers of air cleaning devices. It can also be used between
media suppliers and end customers with regards to loose fill media properties.
— ISO 10121-2 provides a standardized interface between suppliers of air cleaning devices and end
customers seeking the most cost-efficient way to employ gas-phase filtration.
— ISO 10121-3 provides a classification system for the specific application of GPACDs in general, ventilation
systems for cleaning of outdoor air polluted by either local urban sources or long-range transboundary
air pollution, or both.
vi
FINAL DRAFT International Standard ISO/FDIS 10121-1:2026(en)
Test method for assessing the performance of gas-phase air
cleaning media and devices for general ventilation —
Part 1:
Gas-phase air cleaning media (GPACM)
1 Scope
This document establishes an objective test method for challenge testing of gas-phase air cleaning media
(GPACM). It covers media utilizing either capture by an adsorption mechanism or a reaction mechanism,
or both. Key requirements for media sample holder design, apparatus properties and validation tests are
specified.
This document applies to three types of GPACM for use in gas-phase air cleaning devices intended for general
filtration applications:
— GPACM-LF (particles of different shape and size intended for e.g. loose fill applications);
— GPACM-FL (flat sheet fabric intended for e.g. flat one layer, pleated or bag type devices);
— GPACM-TS (three-dimensional structures that are many times thicker than flat sheet and, for example,
used as finished elements in a device).
This document does not apply to:
— generation of test data with the purpose of predicting performance in a real situation since elevated
challenge concentrations are used in the test method;
— a direct comparison between different GPACM types;
— testing of complete devices, which is described in ISO 10121-2;
— general material evaluation or pore system characterization.
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.
ASTM D2854-09, Standard Test Method for Apparent Density of Activated Carbon
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
absorption
transport and dissolution of one substance into another to form a mixture having the characteristics of a
solution
[SOURCE: ISO 29464:2024, 3.5.1]
3.2
adsorbate
molecular compound in gaseous or vapour phase that can be retained by the adsorbent medium
[SOURCE: ISO 29464:2024, 3.5.3]
3.3
adsorbent
solid material having the ability to retain gases or vapour on its surface through physical or chemical
processes
[SOURCE: ISO 29464:2024, 3.5.4]
3.4
adsorption isotherm
relationship between the amount of a gas physically adsorbed on a surface and the partial pressure of the
gas at constant temperature
3.5
adsorption
process in which the molecules of a gas or vapour adhere by physical or chemical processes to the exposed
surface of solid substances, both the outer surface and inner pore surface, with which they come into contact
[SOURCE: ISO 29464:2024, 3.5.7]
3.6
breakthrough
amount of gaseous contaminant in the effluent (i.e. downstream) of a gas-phase air cleaning medium sample
under test
Note 1 to entry: See penetration (3.35).
3.7
bypass
proportion of the challenge air stream that passes around or through an air cleaner without interacting with
the air cleaner
[SOURCE: ISO 29464:2024, 3.1.5]
3.8
capacity
m
s
amount (mass or moles) of a selected sorbate that can be contained in the gas-phase air cleaning medium or
device at given test conditions, and a specific end point
Note 1 to entry: Capacity can also be negative during desorption.
3.9
challenge concentration
concentration of the test contaminant(s) of interest in the air stream prior to filtration (challenge air stream)
[SOURCE: ISO 29464:2024, 3.5.16]

3.10
challenge compound
chemical compound that is being used as the contaminant of interest for any given test
[SOURCE: ISO 29464:2024, 3.5.15]
3.11
challenge air stream
test contaminant(s) of interest diluted to the specified concentration(s) of the test prior to filtration
[SOURCE: ISO 29464:2024, 3.5.14]
3.12
channelling
disproportionate or uneven flow of gas through passages of lower resistance due to inconsistencies in the
design or production of a gas-phase air cleaning device, particularly in packed granular beds
[SOURCE: ISO 29464:2024, 3.5.17]
3.13
chemisorption
chemical adsorption
trapping of gaseous or vapour contaminants on an adsorbent involving chemical reaction on the adsorbent
surface
[SOURCE: ISO 29464:2024, 3.5.19]
3.14
concentration
C
n
quantity of one substance dispersed in a defined amount of another
Note 1 to entry: Indice “n” denotes location or origin.
[SOURCE: ISO 29464:2024, 3.1.11, modified — symbol added as admitted term; note 1 to entry has been
added.]
3.15
contaminant
substance (solid, liquid, or gas) that negatively affects the intended use of a gas
[SOURCE: ISO 29464:2024, 3.1.12]
3.16
decay time
t
Dn
time required for the gas contaminant monitoring instrument to record a reduction from an initial
value greater than 95 % of the challenge concentration to a final value of less than 5 % of the challenge
concentration (t - t ) at the downstream sampling point for a specific test (n), challenge gas and gas flow
END VC
rate after stopping the injection of the contaminant with no gas-phase air cleaning media or device present
[SOURCE: ISO 29464:2024, 3.5.21, modified — symbols have been added to the definition.]
3.17
desorption
process in which adsorbate molecules leave the surface of the adsorbent and re-enter the air stream
Note 1 to entry: Desorption is the opposite of adsorption.
[SOURCE: ISO 29464:2024, 3.5.22]

3.18
diffusor
device that forces the air stream to achieve an even face velocity over the entire cross-sectional area of a test
duct
Note 1 to entry: The device can be a perforated plate.
3.19
downstream
area or region into which air flows on leaving an air cleaner
[SOURCE: ISO 29464:2024, 3.1.16]
3.20
removal efficiency versus time curve
plot of the gas-phase air cleaning medium or device removal efficiency against time over the duration of a
challenge test for a particular challenge concentration and air flow rate
[SOURCE: ISO 29464:2024, 3.5.58, modified — the word "rate" has been added.]
3.21
removal efficiency versus capacity curve
plot of the gas-phase air cleaning device removal efficiency against the integrated capacity over the duration
of a challenge test for a particular challenge concentration and air flow rate
[SOURCE: ISO 29464:2024, 3.5.56, modified — the word "rate" has been added.]
3.22
face velocity
volumetric air flow rate divided by the nominal air cleaner face area
Note 1 to entry: Air cleaner face velocity is expressed in m/s (fpm).
[SOURCE: ISO 29464:2024, 3.1.20]
3.23
gas
substance whose vapour pressure is greater than the ambient pressure at ambient temperature
[SOURCE: ISO 29464:2024, 3.1.34]
3.24
gas-phase air cleaning device
GPACD
assembly of a fixed size enabling the removal of specific gas- or vapour-phase contaminants
Note 1 to entry: It is normally box shaped or fits into a box of dimensions between 290 mm × 290 mm × 290 mm up to
approximately 610 mm × 610 mm × 610 mm or 2 feet × 2 feet × 2 feet.
[SOURCE: ISO 29464:2024, 3.5.34]
3.25
GPAC medium or device face area
cross-sectional area of the gas-phase air cleaning (GPAC) medium or device also including a header frame or
other support structures if so equipped when viewed from the direction of air flow using exact dimensions
[SOURCE: ISO 29464:2024, 3.5.36]

3.26
gas-phase air cleaning medium
GPACM
solid medium or medium configuration used for filtering a contaminant
EXAMPLE A porous film or fibrous layer; a bead shaped, granular or pelletized adsorbent (or chemisorbent); a
support structure of fabric, foam or monoliths containing adsorbent in the form of small sized particles, granules,
spheres or powder; a woven or nonwoven fabric completely made from an adsorbent material.
[SOURCE: ISO 29464:2024, 3.5.37]
3.27
gas-phase air cleaning medium – loose filled
GPACM-LF
adsorbent in the form of particles of different shape and size intended for loose fill applications, for example
[SOURCE: ISO 29464:2024, 3.5.39]
3.28
gas-phase air cleaning medium – flat sheet layer
GPACM-FL
adsorbent in the form of flat sheet that is flexible, thin, and nominally two-dimensional
EXAMPLE Woven or nonwoven fabrics, wet laid papers, smooth pads, felts etc. normally handled as roll goods.
[SOURCE: ISO 29464:2024, 3.5.38]
3.29
gas-phase air cleaning medium – three-dimension structure
GPACM-TS
adsorbent in the form of a three-dimensional structure that is many times thicker than flat sheet and used
as a finished element in a device
EXAMPLE Flexible open cell structures, i.e. of thicker impregnated foam, corrugated pads etc. and air permeable
rigid structures, i.e. of bonded particles, honeycomb trays, extruded monoliths, etc.
[SOURCE: ISO 29464:2024, 3.5.40]
3.30
initial efficiency
E
i
efficiency calculated as the intersection of vertical efficiency axis by extrapolation of a linear fit of efficiency
versus time from the values between 2 min to 12 min of the removal efficiency (E) versus time graph
generated during testing of a gas-phase air cleaning medium or device
3.31
molecular contamination
contamination present in gas or vapour phase in an air stream and excluding compounds in particulate
(solid) phase regardless of their chemical nature
[SOURCE: ISO 29464:2024, 3.5.43]
3.32
ppb(v)
parts per billion by volume concentration measure normally used to record ambient levels of outdoor
pollution
3 3
Note 1 to entry: Units are mm /m .
[SOURCE: ISO 29464:2024, 3.5.46]

3.33
ppm(v)
parts per million by volume concentration measure normally used to record pollution levels in, for example,
work place safety
3 3 3
Note 1 to entry: Units are cm /m and ml/m .
[SOURCE: ISO 29464:2024, 3.5.47]
3.34
penetration
P
ratio of contaminant concentration downstream of an air cleaner to the upstream (challenge) concentration
Note 1 to entry: Sometimes expressed as a percentage.
Note 2 to entry: Penetration (P) related to removal efficiency (E) by the expression: E = (1 – P) × 100 %.
Note 3 to entry: Penetration is related to the decontamination factor (DF) by the expression: DF = 1/penetration.
[SOURCE: ISO 29464:2024, 3.1.41]
3.35
physisorption
physical adsorption
attraction of an adsorbate to the surface, both outer surface and inner pore surface, of an adsorbent by
physical forces (Van der Waals forces)
[SOURCE: ISO 29464:2024, 3.5.48]
3.36
pore
minute passageway through which gas can pass or that exposes to the gas stream the internal surfaces of an
adsorbent medium
[SOURCE: ISO 29464:2024, 3.5.49]
3.37
pressure drop
Δp
difference in pressure between two points in an air flow system at specified conditions, especially when
measured across a gas-phase air cleaning medium or device
3.38
removal efficiency
E
fraction or percentage of a challenge contaminant that is removed by an air cleaner
[SOURCE: ISO 29464:2024, 3.1.17]
3.39
retentivity
m
r
measure of the ability of an adsorbent or gas-phase air cleaning device to resist desorption of an adsorbate
Note 1 to entry: Computed as the residual capacity (fraction remaining) after purging the adsorbent with clean,
conditioned air only, following challenge breakthrough.
[SOURCE: ISO 29464:2024, 3.5.63]

3.40
residence time
t
r
relative time that an increment of gas (or contaminant) is within the boundaries of the medium volume
Note 1 to entry: An example of the medium volume is a bed of granules or a non-woven sheet.
Note 2 to entry: In typical use and in this document, this value neglects the fact that the medium and possible support
structures occupy a significant portion of the volume of the bed (residence time is calculated as total bed volume/air
flow rate).
[SOURCE: ISO 29464:2024, 3.5.62]
3.41
rise time
t
Rn
time between initial injection of contaminant and reaching 95 % of the challenge concentration for an empty
duct (t - t ) measured at the downstream sampling location
0 VO
Note 1 to entry: Rise time is specific to a particular test, challenge gas and gas flow rate.
[SOURCE: ISO 29464:2024, 3.5.42, modified — symbol "(t - t )" has been added to the definition; "lag time"
0 VO
has been removed as an admitted term.]
3.42
sorbate
molecular compounds that are retained in the adsorbent of the device
Note 1 to entry: The sorbate will refer to both intended compounds like the selected challenge gas in a test or pollution
in real service but also any other compounds present in the air stream, e.g. gases and vapours.
[SOURCE: ISO 29464:2024, 3.5.65]
3.43
vapour
substance whose vapour pressure is less than the ambient pressure at ambient temperature, but is present
in the gas phase through evaporation or sublimation
[SOURCE: ISO 29464:2024, 3.5.71]
4 Symbols and abbreviated terms
4.1 Symbols
C concentration
C downstream concentration [ppb, ppm] measured at a position Y mm after the media sample or
D
device
C upstream concentration [ppb, ppm] measured at a position X mm before the media sample or device
U
d average particle diameter of a loose fill adsorbent
pa
E removal efficiency [%] for the device measured at the challenge concentration selected during
C
the capacity test
E efficiency recorded at stop test time or value agreed between user and supplier [%]
END
m retentivity; [g],[mol] the amount withheld by the media or device after ventilating with clean
r
air at the same air flow rate selected during the capacity test until C reaches a specified value
D
close to zero.
m total integrated amount [g], [mol] of challenge compound accumulated by the GPAC media or
s
device during the whole challenge test
m integrated amount in moles or gram of challenge compound accumulated during measurement
sD
at the downstream position
m integrated amount in moles or gram of challenge compound accumulated during measurement
sU
at the upstream position
n number of pores along the (shortest) diameter of a GPACM-TS sample
p
p downstream pressure [Pa] measured at a position Y mm after the media sample or device
D
p upstream pressure [Pa] measured at a position X mm before the media sample or device
U
Q air flow rate; used in test (given by 5.4 or 5.5) [m /h] measured at a position Z mm from the
media sample or device
Q average air flow rate calculated from individual measurements evenly distributed over the test
A
period.
φ downstream relative humidity [%] measured at a position Y mm after the media sample or device
D
φ upstream relative humidity [%] measured at a position X mm before the media sample or device
U
t time
t start time. The time when c (contamination concentration upstream) equals the selected chal-
0 u
lenge concentration for an empty sample holder or duct
t decay time for challenge concentration used in the capacity measurement
DC
t time when a test is stopped. The time when a desired concentration or other termination criteria
END
have been met in any of the prescribed test procedures. (The termination criteria are agreed
between user and supplier)
t rise time for challenge concentration used in the capacity measurement
RC
t time noted at challenge gas valve closure
VC
t time noted at challenge gas valve opening
VO
T downstream temperature [°C] measured at a position Y mm after the media sample or device
D
T upstream temperature [°C] measured at a position X mm before the media sample or device
U
v face velocity [m/s] calculated from air flow rate and cross-sectional area of media sample or device
f
X a position X positioned sufficiently far ahead of the sample to allow undisturbed measurements,
verified in the validation Annex A. At the position X the challenge compound is sufficiently mixed
and represents the upstream concentration that is subjected to the GPACM sample.
x minimum recommended distance from the highest part of the sample holder with the same di-
ameter as the upstream side of the sample

Y a position Y positioned sufficiently far after the sample to allow undisturbed measurements,
verified in the validation Annex A. At the position Y the penetrating challenge compound is suf-
ficiently mixed and represents the average downstream concentration after the GPACM sample
y minimum recommended distance from the downstream side of the sample to the lowest part of
the sample holder with the same diameter as the sample
Z a position Z positioned sufficiently far from the media or device to permit a reliable air flow rate
measurement using an orifice device, verified in the Annex A
Δp pressure drop measured over the tested media sample or device [Pa]
4.2 Abbreviated terms
ASHRAE American Society of Heating Refrigerating and Air-conditioning Engineers
ASTM ASTM International, formerly known as the American Society for Testing and Materials (ASTM)
GPAC gas-phase air cleaning
GPACD gas-phase air cleaning device
GPACM gas-phase air cleaning medium/media
HEPA high efficiency particulate air (filter)
JIS Japanese Industrial Standards
JSA Japanese Standards Association
MFC mass flow controller
MSDS material safety data sheet
NMP N-Methyl-2-pyrrolidone
VOC volatile organic compound
5 Testing of different GPACM configurations
5.1 General
This document shows how to measure four key parameters that reflect the performance of a GPACM. The
four parameters are:
— pressure drop, Δp;
— capacity, m ;
s
— removal efficiency, E;
— retentivity, m .
r
These parameters are:
— linked to each other;
— different for different challenge compounds (exception; Δp is not affected);
— different for different concentrations of the same challenge compound (exception; Δp is not affected);
— affected by other gases present, by temperature, by humidity and by the air flow rate;

— different for different particle sizes of loose fill samples occupying the same volume;
— different for identical materials subjected to different face velocities and/or material thicknesses.
The tests are conducted in an air stream and the GPACM configurations are challenged with test compounds
under steady-state conditions. In order to perform tests at sufficiently short test times the concentration is
strongly increased to accelerate the test. In 5.4, two concentration levels are suggested for the determination
of capacity.
Clause 5 describes the required part of the test rig and the required sample holder for different GPACM,
the required parameters for generation of the challenge air stream and test compounds for benchmark
purposes. Clause 6 describes in detail the test sequence for conditioning and for determination of pressure
drop, removal efficiency, capacity and retentivity in this order.
5.2 Test setup and normative GPACM sample holder
The GPACM sample holder shall be installed without leakages or bypass. The air stream should be uniformly
mixed and with equal velocity and upstream concentration over the cross-section. A schematic view of the
sample holder is shown in Figure 1. Recorded parameters are concentration C, pressure p, temperature T and
relative humidity φ in two positions. The air flow rate is recorded at a third position that can be upstream
or downstream of the sample holder. The sample holders should be vertical, and the air flow direction is
most logically from top to bottom as indicated in Figure 1. In this way, bed disturbances e.g. channelling
due to the air flow can be minimized. However, if spring loaded screens are used to hold the material, the air
flow direction can be from bottom to top as well. This document exemplifies the procedure of measuring a
single sample. A test rig with multiple parallel sample holders is often used and can be advantageous. The
procedure can easily be expanded to work with multiple measurements as described in 6.1.

Key
1 example of air flow rate measurement device location at point Z
2 upstream sampling point for T , φ , p and C at point X
U U U U
3 diffusor at a distance x from the media sample surface
4 GPAC media sample of diameter D and thickness h (see Annex D)
5 diffusor at a distance y from the media sample surface
6 downstream sampling point for T , φ , p and C at point Y
D D D D
NOTE Required parameters are given in Annex D.
Figure 1 — Schematic view of a sample holder showing ducting, measurement parameters and
sampling points
Media are used in different configurations depending on the configuration and construction of the intended
device. To cover most applications, three different GPACM configurations are defined. The three different
types identified in this document are:
— GPACM-LF (particles of different shape and size intended for e.g. loose fill applications);
— GPACM-FL (flat sheet fabric intended for e.g. flat one layer, pleated or bag type devices);
— GPACM-TS (three dimensional structures that are many times thicker than flat sheets and e.g. used as
finished elements in a device).
For each of these three GPACM configurations, required dimensions of the sample holder shall be in
accordance with Annex D. Annex D also specifies the sample (bed) thickness, sample face velocity, the
prescribed sampling and filling procedure, which shall be used for each sample holder.

It is also common to test parts of devices e.g. cut out sections from a complete GPACD. These can be tested
according to ISO 10121-2 with the air flow rate adjusted to the remaining cross-section of the sample to
arrive at the same face velocity as for the complete GPACD. Since a unique adaptor plate is used depending
on size and type of GPACD, no specific test configuration can be defined. This test is therefore not part of this
document.
The test equipment supporting the required sample holder can be designed in various ways and it is
not the purpose of this document to enforce a particular engineering solution or analysis technique. A
schematic design is however shown in Annex C. Challenge compound generation and analysis techniques are
recommended in Annex B. The user of this document should select the most appropriate solution with regard
to equipment availability and other technical concerns e.g. single or multiple parallel sample capacity. There
are some key parameters that can severely skew the data or make benchmark testing impossible unless
they are controlled wit
...

ISO/TC 142
Secretariat: UNI
Date: 2026-05-1109-08
Test methodsmethod for assessing the performance of gas-phase air
cleaning media and devices for general ventilation —
Part 1:
Gas-phase air cleaning media (GPACM)
Méthodes d'essai pour l'évaluation de la performance des médias et des dispositifs de filtration moléculaire
pour la ventilation générale — Partie 1: Médias de filtration moléculaire (GPACM)
Partie 1: Médias de filtration moléculaire (GPACM)
FDIS stage
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ISO #####-#:####(X/FDIS 10121-1:2026(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
© ISO #### 2026 – All rights reserved
ii
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 8
4.1 Symbols . 8
4.2 Abbreviated terms . 9
5 Testing of different GPACM configurations . 10
5.1 General. 10
5.2 Test setup and normative GPACM sample holder . 11
5.3 Raw data, sampling accuracy and normative generation parameters . 14
5.4 Test parameters for the standardized benchmark test . 15
5.5 Test parameters selected between user and supplier . 17
6 Test sequence . 18
6.1 General. 18
6.2 Conditioning and pressure drop determination . 18
6.3 Capacity determination . 19
6.4 Retentivity determination . 24
7 Validation of test setup . 25
7.1 General. 25
7.2 Determination of rise time and decay time . 25
8 Evaluation and report . 28
8.1 Test report introduction . 28
8.2 Test report example . 28
Annex A (normative) Test equipment requirements, equipment validation and routine
operation . 34
Annex B (informative) Challenge compounds, generation sources and analysis techniques . 38
Annex C (informative) Design of a media test rig . 44
Annex D (normative) Required sampling procedures and test parameters for different GPACM47
Bibliography . 54

iii
ISO #####-#:####(X/FDIS 10121-1:2026(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 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 142, Cleaning equipment for air and other gases,
in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 195,
Cleaning equipment for air and other gases, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 10121-1:2014), which has been technically
revised.
The main changes are as follows:
— — terms and definitions have been updated to conform with ISO 29464:2024;
— — test compounds have been reviewed in Annex BAnnex B. Challenge concentration recommendations
have been removed for compounds requiring special attention, ozone concentration have been lowered,
and all other challenge concentrations conform with ISO 10121-2 and ISO 10121-3;
— 6.2.1, 6.3.1, 6.4.1, 6.3.3, 6.4.2— 6.2.1, 6.3.1, 6.4.1, 6.3.3, 6.4.2, 7.2.1, 7.2.2 have been reworded
and clarified. In addition, challenge gas, species or compound have been changed to compound unless a
specific gas, e.g. SO , is discussed.
A list of all parts in the ISO 10121 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.

© ISO #### 2026 – All rights reserved
iv
Introduction
There is an increasing use and need for gas-phase filtration in general filtration applications. This demand can
be expected to increase rapidly due to the increasing pollution problems in the world together with an
increasing awareness that solutions to the problems are available in the form of filtration devices or phrased
more technically: gas-phase air cleaning devices (GPACD). The performance of devices using adsorption for
gas removal relies to a large extent on the performance of a solid gas-phase air cleaning media (GPACM)
incorporated in the device. Still, applications, device performance and media performance are often poorly
understood by the user and supplier of such media and devices. Media tests can also be adequate to offer data
for real applications if actual low concentrations (<100 ppb) and longer exposure times (>weeks) can be used
in the test, provided that the geometrical configuration, packing density and air flow conditions of the small-
scale test specimen are equal to those used in the real applications. Such tests are however not included in the
scope of this document. This document attempts to increase understanding and communication by supplying
a more standardized interface between media suppliers, device suppliers and end users. Other standards exist
[1] [1] [2]
for general ventilation in Japan by (JIS B 9901), , Automotive automotive filters by ISO, 11155-2, in-duct
[ ] [2] [3]
sorptive media gas-phase air-cleaning devices by (ASHRAE 145.2 ) and for adsorptive media by (ASHRAE
[3] [5] [5]
145.1) and ASTM . E 300-3. The first edition of the ISO 10121 series was the first international
standardInternational Standard for general gas phase filtration.
This document provides methods, test equipment, data interpretation and reporting for three different types
of gas-phase air cleaning media (GPACM) intended for use in gas-phase air cleaning devices (GPACDGPACDs)
for general ventilation applications.
In addition, information is given in a number of Annexesthe following annexes:
— Annex A— Annex A describes the normative validation procedure in detail in a tabulated form.;
— Annex B— Annex B gives a list of possible test compounds, generation sources and suggests proper
analysis equipment for common test compounds;
— Annex C— Annex C describes the design of the test rig except the normative sample holder.;
— Annex D— Annex D describes the normative test setup and normative section of the test rig for the three
different media configurations.
A general introduction to molecular filtration and molecular filtration testing can be found in the scientific
literature.
The ISO 10121 series consist of three parts.
— — ISO 10121-1 (this document) covers three different media configurations and provideprovides a
standardized interface between media suppliers and producers of air cleaning devices. It can also be used
between media suppliers and end customers with regards to loose fill media properties.
— — ISO 10121-2 provides a standardized interface between suppliers of air cleaning devices and end
customers seeking the most cost-efficient way to employ gas-phase filtration.
— — ISO 10121-3 provides a classification system for the specific application of GPACDs in general,
ventilation systems for cleaning of outdoor air polluted by either local urban sources or long-range
transboundary air pollution, or both.
v
DRAFT International Standard ISO/FDIS 10121-1:2026(Ed.2)

Test methodsmethod for assessing the performance of gas-phase air
cleaning media and devices for general ventilation —
Part 1:
Gas-phase air cleaning media (GPACM)
1 Scope
This document establishes an objective test method for challenge testing of gas-phase air cleaning media
(GPACM). It covers media utilizing either capture by an adsorption mechanism or a reaction mechanism, or
both. Key requirements for media sample holder design, apparatus properties and validation tests are
specified.
This document applies to three types of GPACM for use in gas-phase air cleaning devices intended for general
filtration applications.:
— — GPACM-LF (particles of different shape and size intended for e.g. loose fill applications),);
— — GPACM-FL (flat sheet fabric intended for e.g. flat one layer, pleated or bag type devices) and,);
— — GPACM-TS (three-dimensional structures that are many times thicker than flat sheet and, for example,
used as finished elements in a device).
This document does not apply to:
— — generation of test data with the purpose of predicting performance in a real situation since elevated
challenge concentrations are used in the test method.;
— — a direct comparison between different GPACM types.;
— — testing of complete devices, which is described in ISO 10121-2.;
— — general material evaluation or pore system characterization.
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.
ASTM D 2854-9D2854-09, Standard Test Method for Apparent Density of Activated Carbon
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
ISO #####-#:####(X/FDIS 10121-1:2026(en)
— — IEC Electropedia: available at https://www.electropedia.org/
3.1 3.1
absorption
transport and dissolution of one substance into another to form a mixture having the characteristics of a
solution
[SOURCE: ISO 29464:2024;, 3.5.1]
3.2 3.2
adsorbate
molecular compound in gaseous or vapour phase that can be retained by the adsorbent medium
[SOURCE: ISO 29464:2024;, 3.5.3]
3.3 3.3
adsorbent
solid material having the ability to retain gases or vapour on its surface through physical or chemical processes
[SOURCE: ISO 29464:2024;, 3.5.4]
3.4 3.4
adsorption isotherm
relationship between the amount of a gas physically adsorbed on a surface and the partial pressure of the gas
at constant temperature
3.5 3.5
adsorption
process in which the molecules of a gas or vapour adhere by physical or chemical processes to the exposed
surface of solid substances, both the outer surface and inner pore surface, with which they come into contact
[SOURCE: ISO 29464:2024;, 3.5.7]
3.6 3.6
breakthrough
amount of gaseous contaminant in the effluent (i.e. downstream) of a GPACMgas-phase air cleaning medium
sample under test
Note 1 to entry: See penetration (3.35(3.35).).

3.7
breakthrough versus time curve
plot of contaminant penetration versus time for a particular challenge concentration and air flow rate
[SOURCE: ISO 29464:2024; 3.5.12]
3.7 3.8
bypass
proportion of the challenge air stream that passes around or through an air cleaner without interacting with
the air cleaner
[SOURCE: ISO 29464:2024;, 3.1.5]
© ISO #### 2026 – All rights reserved
3.8 3.9
capacity
m
s
amount (mass or moles) of a selected sorbate that can be contained in the GPAC Mediagas-phase air cleaning
medium or Devicedevice at given test conditions, and a specific end point
Note 1 to entry: Capacity can also be negative during desorption.
3.9 3.10
challenge concentration
concentration of the test contaminant(s) of interest in the air stream prior to filtration (challenge air stream)
[SOURCE: ISO 29464:2024;, 3.5.16]
3.10 3.11
challenge compound
chemical compound that is being used as the contaminant of interest for any given test
[SOURCE: ISO 29464:2024;, 3.5.15]
3.11 3.12
challenge air stream
test contaminant(s) of interest diluted to the specified concentration(s) of the test prior to filtration
[SOURCE: ISO 29464:2024;, 3.5.14]
3.12 3.13
channelling
disproportionate or uneven flow of gas through passages of lower resistance due to inconsistencies in the
design or production of a GPACDgas-phase air cleaning device, particularly in packed granular beds
[SOURCE: ISO 29464:2024;, 3.5.17]
3.13 3.14
chemisorption
chemical adsorption
trapping of gaseous or vapour contaminants on an adsorbent involving chemical reaction on the adsorbent
surface
[SOURCE: ISO 29464:2024;, 3.5.19]
3.14 3.15
concentration
C
n
quantity of one substance dispersed in a defined amount of another
Note 1 to entry: Indice “n” denotes location or origin.
[SOURCE: ISO 29464:2024;, 3.1.11 – Modified:, modified — symbol added as admitted term; note 1 to entry
has been added].]
3.15 3.16
contaminant
substance (solid, liquid, or gas) that negatively affects the intended use of a gas
[SOURCE: ISO 29464:2024;, 3.1.12]
ISO #####-#:####(X/FDIS 10121-1:2026(en)
3.16 3.17
decay time
tDn
time required for the gas contaminant monitoring instrument to record a reduction from an initial value
greater than 95 % of the challenge concentration to a final value of less than 5 % of the challenge concentration
(t - t ) at the downstream sampling point for a specific test (n), challenge gas and gas flow rate after
END VC
stopping the injection of the contaminant with no GPACgas-phase air cleaning media or device present
[SOURCE: ISO 29464:2024;, 3.5.21], modified — symbols have been added to the definition.]
3.17 3.18
desorption
process in which adsorbate molecules leave the surface of the adsorbent and re-enter the air stream
Note 1 to entry: Desorption is the opposite of adsorption.
[SOURCE: ISO 29464:2024;, 3.5.22]
3.18 3.19
diffusor
device that forces the air stream to achieve an even face velocity over the entire cross-sectional area of a test
duct
Note 1 to entry: The device can be a perforated plate.
3.19 3.20
downstream
area or region into which air flows on leaving an air cleaner
[SOURCE: ISO 29464:2024;, 3.1.16]
3.20 3.21
removal efficiency versus time curve
plot of the GPACgas-phase air cleaning medium or device removal efficiency against time over the duration of
a challenge test for a particular challenge concentration and air flow rate
[SOURCE: ISO 29464:2024;, 3.5.58 – Modified:, modified — the word "rate" has been added].]
3.21 3.22
removal efficiency versus capacity curve
plot of the GPACDgas-phase air cleaning device removal efficiency against the integrated capacity over the
duration of a challenge test for a particular challenge concentration and air flow rate
[SOURCE: ISO 29464:2024;, 3.5.56– Modified:, modified — the word "rate" has been added].]
3.22 3.23
face velocity
volumetric air flow rate divided by the nominal air cleaner face area
Note 1 to entry: Air cleaner face velocity is expressed in m/s (fpm).
[SOURCE: ISO 29464:2024;, 3.1.20]
3.23 3.24
gas
substance whose vapour pressure is greater than the ambient pressure at ambient temperature
© ISO #### 2026 – All rights reserved
[SOURCE: ISO 29464:2024;, 3.1.34]
3.24 3.25
gas-phase air cleaning device
GPACD
assembly of a fixed size enabling the removal of specific gas- or vapour-phase contaminants
Note 1 to entry: It is normally box shaped or fits into a box of dimensions between 290 mm × 290 mm × 290 mm up to
approximately 610 mm × 610 mm × 610 mm or 2 feet × 2 feet × 2 feet.
[SOURCE: ISO 29464:2024;, 3.5.34]
3.25 3.26
GPAC medium or device face area
cross-sectional area of the gas-phase air cleaning (GPAC) medium or device also including a header frame or
other support structures if so equipped when viewed from the direction of air flow using exact dimensions
[SOURCE: ISO 29464:2024;, 3.5.36]
3.26 3.27
gas-phase air cleaning medium
GPACM
solid medium or medium configuration used for filtering a contaminant
EXAMPLE : A porous film or fibrous layer; a bead shaped, granular or pelletized adsorbent (or chemisorbent); a
support structure of fabric, foam or monoliths containing adsorbent in the form of small sized particles, granules, spheres
or powder; a woven or nonwoven fabric completely made from an adsorbent material.
[SOURCE: ISO 29464:2024;, 3.5.37]
3.28
3.27
gas-phase air cleaning medium – loose filled
GPACM-LF
adsorbent in the form of particles of different shape and size intended for loose fill applications, for example
[SOURCE: ISO 29464:2024;, 3.5.39]
3.29
3.28
gas-phase air cleaning medium – flat sheet layer
GPACM-FL
adsorbent in the form of flat sheet that is flexible, thin, and nominally two-dimensional
EXAMPLE : Woven or nonwoven fabrics, wet laid papers, smooth pads, felts etc. normally handled as roll goods.
[SOURCE: ISO 29464:2024;, 3.5.38]
3.30
3.29
gas-phase air cleaning medium – three-dimension structure
GPACM-TS
adsorbent in the form of a three-dimensional structure that is many times thicker than flat sheet and used as
a finished element in a device
ISO #####-#:####(X/FDIS 10121-1:2026(en)
EXAMPLE : Flexible open cell structures, i.e. of thicker impregnated foam, corrugated pads etc. and air permeable
rigid structures, i.e. of bonded particles, honeycomb trays, extruded monoliths, etc.
[SOURCE: ISO 29464:2024;, 3.5.40]
3.273.30 3.31
initial efficiency
E
i
efficiency calculated as the intersection of vertical efficiency axis by extrapolation of a linear fit of efficiency
versus time from the values between 2 min to 12 min of the removal efficiency (E) versus time graph
generated during testing of a GPAC mediagas-phase air cleaning medium or device
3.283.31 3.32
molecular contamination
contamination present in gas or vapour phase in an air stream and excluding compounds in particulate (solid)
phase regardless of their chemical nature
[SOURCE: ISO 29464:2024;, 3.5.43]
3.293.32 3.33
ppb(v)
parts per billion by volume concentration measure normally used to record ambient levels of outdoor
pollution
3 3
Note 1 to entry: Units are mm /m .
[SOURCE: ISO 29464:2024;, 3.5.46]
3.303.33 3.34
ppm(v)
parts per million by volume concentration measure normally used to record pollution levels in, for example,
work place safety
3 3 3
Note 1 to entry: Units are cm /m and ml/m .
[SOURCE: ISO 29464:2024;, 3.5.47]
3.313.34 3.35
penetration
P
ratio of contaminant concentration downstream of an air cleaner to the upstream (challenge) concentration
Note 1 to entry: Sometimes expressed as a percentage.
Note 2 to entry: Penetration (P) related to removal efficiency (E) by the expression: E = (1 – P) × 100 %.
Note 3 to entry: Penetration is related to the decontamination factor (DF) by the expression: DF = = 1/penetration.
[SOURCE: ISO 29464:2024;, 3.1.41]
3.323.35 3.36
physisorption
physical adsorption
attraction of an adsorbate to the surface, both outer surface and inner pore surface, of an adsorbent by physical
forces (Van der Waals forces)
© ISO #### 2026 – All rights reserved
[SOURCE: ISO 29464:2024;, 3.5.48]
3.37
pores
3.36
pore
minute passagewayspassageway through which gas can pass or that exposeexposes to the gas stream the
internal surfaces of an adsorbent medium
[SOURCE: ISO 29464:2024;, 3.5.49]
3.333.37 3.38
pressure drop
Δp
difference in pressure between two points in an air flow system at specified conditions, especially when
measured across a GPACgas-phase air cleaning medium or device
3.343.38 3.39
removal efficiency
E
fraction or percentage of a challenge contaminant that is removed by an air cleaner
[SOURCE: ISO 29464:2024;, 3.1.17]
3.353.39 3.40
retentivity
m
r
measure of the ability of an adsorbent or GPACDgas-phase air cleaning device to resist desorption of an
adsorbate
Note 1 to entry: Computed as the residual capacity (fraction remaining) after purging the adsorbent with clean,
conditioned air only, following challenge breakthrough.
[SOURCE: ISO 29464:2024;, 3.5.63]
3.363.40 3.41
residence time
t
r
relative time that an increment of gas (or contaminant) is within the boundaries of the medium volume
Note 1 to entry: An example of the medium volume is a bed of granules or a non-woven sheet.
Note 2 to entry: In typical use and in this document, this value neglects the fact that the medium and possible support
structures occupy a significant portion of the volume of the bed (residence time is calculated as total bed volume/air flow
rate).
[SOURCE: ISO 29464:2024;, 3.5.62]
3.373.41 3.42
rise time
t
Rn
time between initial injection of contaminant and reaching 95 % of the challenge concentration for an empty
duct (t - t ) measured at the downstream sampling location
0 VO
Note 1 to entry: Rise time is specific to a particular test, challenge gas and gas flow rate.
ISO #####-#:####(X/FDIS 10121-1:2026(en)
[SOURCE: ISO 29464:2024;, 3.5.42], modified — symbol "(t - t )" has been added to the definition; "lag time"
0 VO
has been removed as an admitted term.]
3.383.42 3.43
sorbate
molecular compounds that are retained in the adsorbent of the device
Note 1 to entry: The sorbate will refer to both intended compounds like the selected challenge gas in a test or pollution
in real service but also any other compounds present in the air stream, e.g. gases and vapours.
[SOURCE: ISO 29464:2024;, 3.5.65]
3.44
sorption
process in which gas or liquid molecules are removed by the GPACM by absorption or adsorption
[SOURCE: ISO 29464:2024; 3.5.66]
3.393.43 3.45
vapour
substance whose vapour pressure is less than the ambient pressure at ambient temperature, but is present in
the gas phase through evaporation or sublimation
[SOURCE: ISO 29464:2024;, 3.5.71]
4 Symbols and abbreviated terms
4.1 Symbols
C concentration
C downstream concentration [ppb, ppm] measured at a position Y mm after the media sample or
D
device
C upstream concentration [ppb, ppm] measured at a position X mm before the media sample or
U
device
d average particle diameter of a loose fill adsorbent
pa
E removal efficiency [%] for the device measured at the challenge concentration selected during
C
the capacity test
E efficiency recorded at stop test time or value agreed between user and supplier [%]
END
m retentivity; [g],[mol] the amount withheld by the media or device after ventilating with clean air
r
at the same air flow rate selected during the capacity test until C reaches a specified value close
D
to zero.
m total integrated amount [g], [mol] of challenge compound accumulated by the GPAC media or
s
device during the whole challenge test
m integrated amount in moles or gram of challenge compound accumulated during measurement
sD
at the downstream position
m integrated amount in moles or gram of challenge compound accumulated during measurement
sU
at the upstream position
n number of pores along the (shortest) diameter of a GPACM-TS sample
p
p downstream pressure [Pa] measured at a position Y mm after the media sample or device
D
© ISO #### 2026 – All rights reserved
p upstream pressure [Pa] measured at a position X mm before the media sample or device
U
Q air flow rate; used in test (given by 5.45.4 or 5.55.5)) [m /h] measured at a position Z mm from
the media sample or device
Q average air flow rate calculated from individual measurements evenly distributed over the test
A
period.
φ downstream relative humidity [%] measured at a position Y mm after the media sample or
D
device
φ upstream relative humidity [%] measured at a position X mm before the media sample or
U
device
t time
t start time. The time when c (contamination concentration upstream) equals the selected
0 u
challenge concentration for an empty sample holder or duct
t decay time for challenge concentration used in the capacity measurement
DC
t time when a test is stopped. The time when a desired concentration or other termination
END
criteria have been met in any of the prescribed test procedures. (The termination criteria are
agreed between user and supplier)
t rise time for challenge concentration used in the capacity measurement
RC
t time noted at challenge gas valve closure
VC
t time noted at challenge gas valve opening
VO
T downstream temperature [°C] measured at a position Y mm after the media sample or device
D
T upstream temperature [°C] measured at a position X mm before the media sample or device
U
v face velocity [m/s] calculated from air flow rate and cross-sectional area of media sample or
f
device
X a position X positioned sufficiently far ahead of the sample to allow undisturbed measurements,
verified in the validation Annex AAnnex A. At the position X the challenge compound is
sufficiently mixed and represents the upstream concentration that is subjected to the GPACM
sample.
x minimum recommended distance from the highest part of the sample holder with the same
diameter as the upstream side of the sample
Y a position Y positioned sufficiently far after the sample to allow undisturbed measurements,
verified in the validation Annex AAnnex A. At the position Y the penetrating challenge
compound is sufficiently mixed and represents the average downstream concentration after the
GPACM sample
y t minimum recommended distance from the downstream side of the sample to the lowest part
of the sample holder with the same diameter as the sample
Z a position Z positioned sufficiently far from the media or device to permit a reliable air flow rate
measurement using an orifice device, verified in the Annex Anormative Annex A
Δp pressure drop measured over the tested media sample or device [Pa]
4.2 Abbreviated terms
ASHRAE American Society of Heating Refrigerating and Air-conditioning Engineers
ASTM ASTM International, formerly known as the American Society for Testing and Materials
(ASTM)
ISO #####-#:####(X/FDIS 10121-1:2026(en)
GPAC gas-phase air cleaning
GPACD gas-phase air cleaning device
GPACM gas-phase air cleaning medium/media
HEPA Highhigh efficiency particulate air (filter)
JIS Japanese industrial standardsIndustrial Standards
JSA Japanese standards associationStandards Association
Mass Flow Controller
MFC
MSDS
Materialmass flow controller
material safety data sheet
NMP nN-Methyl −-2-pyrrolidone
VOC Volatilevolatile organic compound
5 Testing of different GPACM configurations
5.1 General
This document shows how to measure four key parameters that reflect the performance of a GPACM. The four
parameters are:
— — pressure drop, Δp;
— — capacity, m ;
s
— — removal efficiency, E;
— — retentivity, m .
r
These parameters are:
— — linked to each other;
— — different for different challenge compounds (exception; Δp is not affected);
— — different for different concentrations of the same challenge compound (exception; Δp is not affected);
— — affected by other gases present, by temperature, by humidity and by the air flow rate;
— — different for different particle sizes of loose fill samples occupying the same volume;
— — different for identical materials subjected to different face velocities and/or material thicknesses.
The tests are conducted in an air stream and the GPACM configurations are challenged with test compounds
under steady-state conditions. In order to perform tests at sufficiently short test times the concentration is
strongly increased to accelerate the test. In 5.4this document, two concentration levels are suggested for the
determination of capacity in 5.4.
Clause 5Clause 5 describes the normativerequired part of the test rig and normativethe required sample
holder for different GPACM, normativethe required parameters for generation of the challenge air stream and
test compounds for benchmark purposes. Clause 6Clause 6 describes in detail the test sequence for
conditioning and for determination of pressure drop, removal efficiency, capacity and retentivity in this order.
© ISO #### 2026 – All rights reserved
NOTE This document does not purport to address all of the safety concerns, if any, associated with its use. The user of
this document should investigate any possible hazard and to take the necessary precautions.

5.2 Test setup and normative GPACM sample holder
The GPACM sample holder shall be installed without leakages or bypass. The air stream should be uniformly
mixed and with equal velocity and upstream concentration over the cross-section. A schematic view of the
sample holder is shown in Figure 1Figure 1. Recorded parameters are concentration C, pressure p,
temperature T and relative humidity φ in two positions. The air flow rate is recorded at a third position that
can be upstream or downstream of the sample holder. The sample holders should be vertical, and the air flow
direction is most logically from top to bottom as indicated in Figure 1Figure 1. In this way, bed disturbances
like e.g. channelling due to the air flow can be minimized. However, if spring loaded screens are used to hold
the material, the air flow direction can be from bottom to top as well. This document exemplifies the procedure
of measuring a single sample. A test rig with multiple parallel sample holders is often used and can be
advantageous. The procedure can easily be expanded to work with multiple measurements as described in
6.16.1.
ISO #####-#:####(X/FDIS 10121-1:2026(en)

© ISO #### 2026 – All rights reserved
Key
1 example of air flow rate measurement device location at point Z
2 upstream sampling point for TU, φU, pU and CU at point X
3 diffusor at a distance x from the media sample surface
4 GPAC media sample of diameter D and thickness h, see the normative Annex D
Key
1 example of air flow rate measurement device location at point Z
2 upstream sampling point for TU, φU, pU and CU at point X
3 diffusor at a distance x from the media sample surface
4 GPAC media sample of diameter D and thickness h (see Annex D)
5 diffusor at a distance y from the media sample surface
6 downstream sampling point for TD, φD, pD and CD at point Y
NOTE Required parameters are given in Annex Dthe normative Annex D.
Figure 1— — Schematic view of a sample holder showing ducting, measurement parameters and
sampling points
Media are used in different configurations depending on the configuration and construction of the intended
device. To cover most applications, three different GPACM configurations are defined. The three different
types identified in this document are:
— GPACM-LF (particles of different shape and size intended for e.g. Loose Fillloose fill applications), );
— GPACM-FL (Flatflat sheet fabric intended for e.g. flat one layer, pleated or bag type devices) and );
ISO #####-#:####(X/FDIS 10121-1:2026(en)
— GPACM-TS (three dimensional structures that are many times thicker than flat sheets and e.g. used as
finished elements in a device). For each of these three GPACM configurations normative measures of the
sample holder are given in the normative Annex D. Annex D also contain specific normative information
for the use of each sample holder including sample (bed) thickness and sample face velocity as well as the
prescribed sampling and filling procedure.
For each of these three GPACM configurations, required dimensions of the sample holder shall be in
accordance with Annex D. Annex D also specifies the sample (bed) thickness, sample face velocity, the
prescribed sampling and filling procedure, which shall be used for each sample holder.
It is also common to test parts of devices e.g. cut out sections from a complete GPACD. These can be tested
according to ISO 10121--2 with the air flow rate adjusted to the remaining cross-section of the sample to arrive
at the same face velocity as for the complete GPACD. Since a unique adaptor plate is used depending on size
and type of GPACD, no normativespecific test sectionconfiguration can be defined. This test is therefore not
part of this document.
The test equipment supporting the normativerequired sample holder can be designed in various ways and it
is not the purpose of this document to enforce a particular engineering solution or analysis technique. A
schematic design is however shown in Annex CAnnex C. Challenge compound generation and analysis
techniques are suggestedrecommended in Annex BAnnex B. It is the. The user of this document that should
select the most appropriate solution best fitted with regard to equipment availability and other technical
concerns e.g. single or multiple parallel sample capacity. There are some key parameters that willcan severely
skew the data or make benchmark testing impossible unless they are controlled within specified limits. These
parameters are displayed in the normativerequired test section in Figure 1Figure 1 and Table 1Table 1. The
adherence to these levels shall be demonstrated by the tests provided in the validation section in Clause 7.
5.3 Raw data, sampling accuracy and normative generation parameters
Ideally, all measurement parameters in Figure 1Figure 1 should be measured continuously with a
computerisedcomputerized logging system. The sampling frequency should be fast enough to produce
sufficient resolution in the adsorption and desorption data. Table 1Table 1 gives required generation
parameters in addition to prescribed accuracy.
Table 1 — Required generation parameters, measurement frequency and demands on accuracy
during test
Paramete Required Unit Range Accuracy Permissi Permissi Measurem
r generation ble mean ble ent
parameter value oscillatio frequency
d
s during n mean
test value
short-
term
(10 min)
CU selected in
5 000 – 5 min, 1 h,
5.45.4 or ppb(v) ±2,0 % ±3 % ±3 %
a, b
100 000 4 h, 12 h
5.55.5
C ±10 ppb
D
(0 – 500 ppb)
b
n.a. ppb(v) 100 – 100 000 n.a. n.a. 1 min
±2,0 %
(500 –
100 000 ppb)
© ISO #### 2026 – All rights reserved
Paramete Required Unit Range Accuracy Permissi Permissi Measurem
r generation ble mean ble ent
parameter value oscillatio frequency
d
s during n mean
test value
short-
term
(10 min)
T 23 or
U
selected in ±0,5 °C ±1 °C
c
°C n.a. ±0,5 °C same as C
D
5.55.5
TD n.a. n.a. n.a.
φ 50 or
U
e e
selected in ±1,5 % ±3 %
c e
% n.a. ±2,0 %
same as CD
5.55.5
φ n.a. n.a. n.a.
D
pU, pD - Pa - ±5 % n.a n.a. same as CD
Δp ±2 Pa
specific for
(0 – 100 Pa)
media and
Pa - ± ± 2 % na. n.a. same as CD
sample
(100 –
holder
10 000 Pa)
Q, air flow givenspecifie
m /h n.a.
d in
rate
±2 % ±1,5 % ±3 % same as CD
Annex Dnor
vf, face m/s n.a.
mative
velocity
Annex D for
5.4 or user
residence s n.a. n.a. n.a. n.a. n.a.
selected in
time
5.55.5
a Upstream concentration needshall be measured, at a minimum to be measured, before and after an individual test sequence.
b A longer interval may be used if at least 100 data points can be generated down to 50 % efficiency. A longer measurement
duration can be neededrequired for concentration to permit low level detection using ex situ equipment e.g. Tenaxspecific
adsorption tubes, resulting in less frequent measurements than every 5 min.
c Useful informative ranges of T and φ are 15 °C to 45 °C and 30 % to 95 % respectively.
d Oscillation referrefers here to a deviation upstream or downstream of a distinct mean value that returns to the mean value. A
ramp-like steady increase or decrease is not permitted. Mean value during test is calculated during the entire test. A short-term
mean value is calculated during an event being maximum 10 min long. More than one short-term event can be permitted.
e The ±% ± % value here refers to percentage points of relative humidity and not to a calculated percentage of a value.
5.4 Test parameters for the standardized benchmark test
5.4.1 General
For generally applicable benchmark purposes, two concentration levels and three gases are suggested and
common for all the GPACM configurations defined in this document. The levels and gases are given in
Table 2Table 2. All other parameters are normativelyrequired as specified in Table 1 but different for
different GPACM configurations given in Annex DAnnex D. The whole test setup is selected as a best
compromise between measurement errors, the resolution of available measurement techniques and
acceptable testing times.
ISO #####-#:####(X/FDIS 10121-1:2026(en)
5.4.2 Challenge test concentration
To ensure that the challenge test can be performed with a test time between 1 h and 12 h, two high
concentrations are given,: 9 ppm(v) and 90 ppm(v). The higher concentration can be needed in order to
ensure that the media is challenged enough to show a decaying efficiency. To ensure that the test is challenging
the media enough to produce useful data, a minimum permissible end efficiency is also given. Data obtained
can be used for comparison of different samples within the same GPACM configuration, providing that the
compared data for both samples were measured at either 9 ppm(v) or 90 ppm(v) with the same challenge gas,
same sample holder and with the same test option i.e. the same face velocity and material height.
5.4.3 GPACMs for VOC tested with toluene
The goal is to select the lower concentration for toluene whenever possible, since the data produced from this
concentration approximate the actual application better. At higher concentrations, the adsorption isotherms
from different adsorbents can change ranking due to pore volume and show an “empty” and easily desorbed
capacit
...