ISO 17168-4:2018

Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for air-purification performance of semiconducting photocatalytic materials under indoor lighting environment - Part 4: Removal of formaldehyde

This document specifies a test method for the determination of the air-purification performance, with regards to the removal of formaldehyde, 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 from indoor light. This document is intended 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 4: Titre manque

General Information

• Status: Published
• Publication Date: 18-Sep-2018
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: ISO/TC 206 - Fine ceramics
• Drafting Committee: ISO/TC 206/WG 9 - Photocatalysis
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 07-Nov-2025
• Completion Date: 13-Dec-2025

Relations

• Revised: ISO 17168-4:2025 - Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for air-purification performance of semiconducting photocatalytic materials under indoor lighting environment - Part 4: Removal of formaldehyde
• Effective Date: 16-Mar-2024
• Revised: ISO 22197-4:2013 - Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for air-purification performance of semiconducting photocatalytic materials - Part 4: Removal of formaldehyde
• Effective Date: 01-Jun-2013

Overview

ISO 17168-4:2018 specifies a laboratory test method for the air‑purification performance of semiconducting photocatalytic materials under indoor lighting conditions, focusing on the removal of formaldehyde (HCHO). The standard applies to materials that contain a photocatalyst or have photocatalytic films-typically semiconducting metal oxides (e.g., titanium dioxide) or ceramic-based composites-exposed continuously to a model formaldehyde pollutant while illuminated by indoor light. It is intended for flat construction materials, boards, plates, honeycomb structures and plastic/paper substrates containing ceramic microcrystals. Powder or granular photocatalysts are excluded.

Key topics and technical requirements

• Test principle: Flow‑type photoreactor exposure of a test piece to a controlled formaldehyde concentration under indoor light; measurement of formaldehyde removed by the material and comparison with dark (non‑illuminated) adsorption to separate photocatalytic activity from simple adsorption.
• Apparatus and setup: Requirements for test gas supply, humidification, gas mixing and flow control (thermal mass‑flow controllers), a photoreactor with defined geometry (air gap between sample and optical window), airtight optical window, indoor light source (cool white lamp) and a UV sharp cut‑off filter as per ISO 14605, plus an analytical system for formaldehyde measurement.
• Test piece specifications: Dimensions and holder configurations for flat and filter‑type samples; special guidance for honeycomb and composite materials; exclusion of powders/granules.
• Operational controls: Flow rate accuracy (within 5%), stable formaldehyde concentration sourcing (standard gas or generator free of impurities), illuminance control and warm‑up/shutter procedures for light sources.
• Data and calculations: Determination of removal quantity (µmol) and removal percentage; separate dark tests to quantify adsorption; special procedures for low‑performance samples.
• Scope limits: Not applicable to other photocatalytic functions such as water contaminant decomposition, self‑cleaning, antifogging or antibacterial performance.

Practical applications and users

• Who uses it: Test laboratories, manufacturers of photocatalytic construction materials and indoor air‑purification products, R&D teams, quality assurance personnel, conformity assessors and spec writers.
• Why use it: To evaluate, compare and certify indoor‑light‑active photocatalytic materials for formaldehyde removal; to support product development, quality control, regulatory claims and performance labeling for building interiors and air‑purifying surfaces.
• Use cases: Performance benchmarking of façade panels, interior wall materials, coatings and honeycomb purifiers; establishing lab test data for product datasheets and third‑party verification.

Related standards

• ISO 17168-1 (Part 1: removal of nitric oxide) - shared test system concepts
• ISO 14605 - light source specification for indoor photocatalyst testing
• ISO 16000-3 - formaldehyde sampling and analysis methods
• ISO 22197 series - related photocatalytic test methods for pollutant removal
• ISO/IEC 17025 - laboratory competence and quality requirements

Keywords: ISO 17168-4:2018, photocatalytic materials, formaldehyde removal, indoor-light-active, fine ceramics, test method, photoreactor, air purification, titanium dioxide.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 17168-4
First edition
2018-09
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Test method for air-purification
performance of semiconducting
photocatalytic materials under indoor
lighting environment —
Part 4:
Removal of formaldehyde
Reference number
©
ISO 2018
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Principle . 2
6 Apparatus . 2
6.1 Test equipment . 2
6.2 Test gas supply . 3
6.3 Photoreactor . 4
6.4 Light source . 6
6.5 UV sharp cut-off filter . 6
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 Preparation for the test . 7
8.4 Pretest . 8
8.5 Removal test . 8
9 Calculation . 8
10 Test method for test pieces with lower performance . 9
11 Test report . 9
Bibliography .11
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
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electrotechnical standardization.
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described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
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URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2018 – All rights reserved

Introduction
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 22197-1, ISO 22197-2 and ISO 22197-3 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 formaldehyde, one of the most interesting aromatic volatile organic compound
(VOC)-caused sick-house syndromes, enabling swift distribution of photocatalytic products and thus
contributing to a safe and clean environment.
INTERNATIONAL STANDARD ISO 17168-4:2018(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for air-purification performance
of semiconducting photocatalytic materials under indoor
lighting environment —
Part 4:
Removal of formaldehyde
1 Scope
This document specifies a test method for the determination of the air-purification performance, with
regards to the removal of formaldehyde, 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
from indoor light.
This document is intended 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 6145-7, Gas analysis — Preparation of calibration gas mixtures using dynamic volumetric methods —
Part 7: Thermal mass-flow controllers
ISO 14605, Fine ceramics (advanced ceramics, advanced technical ceramics) — Light source for testing
semiconducting photocatalytic materials used under indoor lighting environment
ISO 16000-3, Indoor air — Part 3: Determination of formaldehyde and other carbonyl compounds in indoor
air and test chamber air — Active sampling method
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 80000-1, Quantities and units — Part 1: General
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 17168-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Symbols
f flow rate of test gas converted into that at the standard state (0 °C, 101,3 kPa)
ϕ formaldehyde volume fraction at the reactor exit (µl/l)
F
ϕ formaldehyde volume fraction at the reactor exit under dark conditions (µl/l)
FD
ϕ supply volume fraction of formaldehyde (µl/l)
F0
n removal quantity, by test piece, of formaldehyde (µmol)
F
R removal percentage, by test piece, of formaldehyde (%)
F
5 Principle
This document deals with the development, comparison, quality assurance, characterization,
[1]
reliability and 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. Formaldehyde (HCHO) is chosen because it is a
[2]
typical indoor air pollutant that causes the so-called sick building syndrome . The test piece, placed
in a flow-type photoreactor, is activated by indoor light illumination, and adsorbs and oxidizes gas-
phase formaldehyde to form carbon dioxide (CO ) and other oxidation products. The air purification
performance is determined from the amount of formaldehyde removed by the test piece (μmol). The
simple adsorption of HCHO by the test piece (not due to photocatalysis) is evaluated by tests in the dark.
However, some test pieces are very absorbent, and a stable concentration of formaldehyde may not be
attained in the designated test time. The photocatalytic activity may 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 tested, the system shall be constructed
with materials of low absorption and resistant to ultraviolet (UV) radiation, for example acrylic resin,
stainless steel, glass and f
...