ISO 17168-5:2025

Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for air-purification performance of semiconducting photocatalytic materials under indoor lighting environment - Part 5: Removal of methyl mercaptan

This document specifies a test method for the determination of the air-purification performance, with regards to removal of methyl mercaptan, of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination with indoor light. This document is applicable for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, which are the basic forms of materials for various applications. This document also applies to materials in honeycomb form, and to plastic or paper materials containing ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions.

Titre manque — Partie 5: Titre manque

General Information

• Status: Published
• Publication Date: 06-Nov-2025
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: ISO/TC 206 - Fine ceramics
• Drafting Committee: ISO/TC 206/WG 9 - Photocatalysis
• Current Stage: 6060 - International Standard published
• Start Date: 07-Nov-2025
• Due Date: 12-Mar-2026
• Completion Date: 07-Nov-2025

Relations

• Revises: ISO 17168-5:2018 - Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for air-purification performance of semiconducting photocatalytic materials under indoor lighting environment - Part 5: Removal of methyl mercaptan
• Effective Date: 16-Mar-2024

Overview

ISO 17168-5:2025 specifies a standardized test method for assessing the air‑purification performance of semiconducting photocatalytic materials under indoor lighting, with a specific focus on the removal of methyl mercaptan (methanethiol). The standard applies to materials that contain a photocatalyst or have photocatalytic films on surfaces (commonly semiconducting metal oxides such as titanium dioxide and related fine ceramics) in flat sheet, board, plate or honeycomb forms, and to plastic/paper composites with ceramic microcrystals. It does not apply to powder or granular photocatalytic materials and is not intended for evaluating other photocatalytic attributes (self‑cleaning, antifogging, antibacterial).

Key topics and technical requirements

• Test principle: Continuous exposure of a test piece in a flow‑type photoreactor to a model pollutant (methyl mercaptan) under controlled indoor‑light illumination; performance derived from net pollutant removal and removal rate. Dark tests distinguish adsorption from photocatalytic oxidation.
• Apparatus & setup:
  • Test gas supply with flow controllers (flow rate accuracy ±5.0 %).
  • Photoreactor holding a planar test piece with a 5.0 mm ±0.5 mm air layer between piece and airtight optical window.
  • Light source: cool white fluorescent lamp with UV sharp cut‑off filter (per ISO 14605) or LED light source (per ISO 24448). Illuminance at sample: 6 000 lx ±300 lx, uniform within ±5 %.
  • Analytical measurement system for low pollutant concentrations and gas‑handling materials resistant to UV and adsorption (acrylic, stainless steel, glass, fluoropolymers).
• Test gases & concentrations: Standard methyl mercaptan cylinders typically balanced in nitrogen with volume fractions in the 100–1 000 µl/l range.
• Test piece dimensions and reactor geometry are specified (e.g., 99.0 mm × 49.0 mm test piece).
• Reporting & quality: Includes calculation of removal quantity and percentage, procedures for low‑performance samples, and requirements consistent with laboratory competence (ISO/IEC 17025 referenced).

Applications and users

• Who uses it: photocatalytic material manufacturers, product developers, independent testing laboratories, certification bodies, architects and specifiers, indoor air quality consultants, and regulatory agencies.
• Practical uses:
  • Product development and R&D for indoor‑active photocatalysts.
  • Quality control and batch comparison of air‑purifying materials.
  • Comparative performance claims and lab‑based certification for odor removal (sulfurous compounds).
  • Material selection for building interiors, ventilation components, and consumer products targeting odor control.

Related standards

• ISO 17168‑1 (Removal of nitric oxide) - foundational test methodology for indoor photocatalytic performance.
• ISO 14605 - light source for indoor testing (fluorescent + UV cut‑off).
• ISO 24448 - LED light source specification for indoor photocatalytic testing.
• ISO/IEC 17025 - laboratory competence and calibration requirements.

Keywords: ISO 17168-5:2025, fine ceramics, photocatalytic materials, air‑purification performance, methyl mercaptan, indoor lighting, titanium dioxide, photoreactor, ISO 14605, ISO 24448.

Standards Content (Sample)

International
Standard
ISO 17168-5
Second edition
Fine ceramics (advanced ceramics,
2025-11
advanced technical ceramics) —
Test method for air-purification
performance of semiconducting
photocatalytic materials under
indoor lighting environment —
Part 5:
Removal of methyl mercaptan
Reference number
© ISO 2025
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
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or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 2
5 Principle . 2
6 Apparatus . 2
6.1 Test equipment .2
6.2 Test gas supply .2
6.3 Photoreactor .3
6.4 Lighit source .5
6.5 UV sharp cut-off filter .5
6.6 Analytical system.6
7 Test piece . 6
8 Procedure . 6
8.1 General aspects .6
8.2 Pretreatment of test piece .7
8.3 Pollutant removal test . .7
9 Calculation . 8
10 Test method for test pieces with lower performance . 9
11 Test report . 9
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
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
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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 206, Fine ceramics.
This second edition cancels and replaces the first edition (ISO 17168-5:2018), which has been technically
revised.
The main changes are as follows:
— normative reference ISO 24448 added to Clause 2 and 6.4.
A list of all parts in the ISO 17168 series can be found on the ISO website.

iv
Introduction
A photocatalyst is a substance that performs decomposition and removal of contaminants, self-cleaning,
antifogging, deodorization and antibacterial actions under photoirradiation. Its application has expanded
considerably in recent years. The application of photocatalysts for indoor spaces has increasingly been
sought as a solution to indoor environmental problems. Since conventional photocatalysts are responsive
only to ultraviolet light, studies have been made to develop an indoor-light-active photocatalyst that makes
effective use of indoor light, which room lights mainly emit, and thus demonstrates high photocatalytic
performance indoors. The development has recently led to the commercialization of various indoor-light-
active photocatalytic products, and there has been demand for the establishment of test methods to evaluate
the performance of this type of photocatalyst.
This document, with ISO 17168-1 and ISO 22197-5 as the basis, is intended to provide a testing method to
determine the performance of indoor-light-active photocatalytic materials with regards to the removal of
methyl mercaptan, enabling swift distribution of photocatalytic products and thus contributing to a safe
and clean environment.
v
International Standard ISO 17168-5:2025(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for air-purification performance
of semiconducting photocatalytic materials under indoor
lighting environment —
Part 5:
Removal of methyl mercaptan
WARNING — The use of this document can involve hazardous materials, operations and equipment.
It is necessary to check that there are no leaks from the gas flow paths, and to properly dispose
of exhaust gas and wastewater. This document does not purport to address all of the safety or
environmental problems associated with its use.
1 Scope
This document specifies a test method for the determination of the air-purification performance, with
regards to removal of methyl mercaptan, of materials that contain a photocatalyst or have photocatalytic
films on the surface, usually made from semiconducting metal oxides such as titanium dioxide or other
ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination with
indoor light.
This document is applicable for use with different kinds of materials, such as construction materials
in flat sheet, board or plate shape, which are the basic forms of materials for various applications. This
document also applies to materials in honeycomb form, and to plastic or paper materials containing
ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic
materials.
This test method is usually applicable to photocatalytic materials produced for air purification. This
method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e.
decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions.
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 14605, Fine ceramics (advanced ceramics, advanced technical ceramics) — Light source for testing
semiconducting photocatalytic materials used under indoor lighting environment
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO 17168-1, Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for air purification
performance of semiconducting photocatalytic materials under indoor lighting environment — Part 1: Removal
of nitric oxide
ISO 24448, Fine ceramics (advanced ceramics, advanced technical ceramics) — LED light source for testing
semiconducting photocatalytic materials used under indoor lighting environment

3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 17168-1 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/
4 Symbols
f flow rate of test gas converted into that at the standard state (0 °C, 101,3 kPa) (l/min)
ϕ methyl mercaptan volume fraction at the reactor exit (µl/l)
M
ϕ supply volume fraction of methyl mercaptan (µl/l)
M0
n removal quantity, by test piece, of methyl mercaptan (µmol)
M
R removal percentage, by test piece, of methyl mercaptan (%)
M
5 Principle
This document deals with the development, comparison, quality assurance, characterization, reliability and
[1]
design data generation of photocatalytic materials . The method described is intended to obtain the air-
purification performance of photocatalytic materials by exposing a test piece to model polluted air under
illumination by indoor light. Methyl mercaptan (methanethiol, CH SH) is chosen as a typical malodorous
[2]
substance . The test piece, placed in a flow-type photoreactor, is activated by indoor-light illumination,
and adsorbs and oxidizes gas-phase methyl mercaptan. The air-purification performance is determined
from the amount of the net removal of methyl mercaptan and removal rate of methyl mercaptan. The simple
adsorption and desorption of CH SH by the test piece (not due to photocatalysis) is evaluated by tests in
the dark. However, this document cannot be applied to test pieces which do not give a stable concentration
of methyl mercaptan in the designated test time. The photocatalytic activity can depend on physical and
chemical properties of pollutants, mainly due to the adsorption process involved. For a better evaluation of
air purification performance of photocatalytic materials, it is recommended that one or more suitable test
methods are combined, as provided in other parts of the ISO 17168 series.
6 Apparatus
6.1 Test equipment
The test equipment enables a photocatalytic material to be examined for its pollutant-removal capability by
supplying the test gas continuously, while providing photoirradiation to activate the photocatalyst. It is the
same as that used in the test method for the removal of nitric oxide (see ISO 17168-1) and consists of a test
gas supply, a photoreactor, a light source, a UV sharp cut-off filter and pollutant measurement equipment.
Since low concentrations of pollutants are to be test
...