ISO 17168-2:2018

INTERNATIONAL ISO
STANDARD 17168-2
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 2:
Removal of acetaldehyde
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
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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

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 . 3
6.1 Test equipment . 3
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 for acetaldehyde . 6
6.7 Analytical system for CO . 7
7 Test piece . 7
8 Procedure. 7
8.1 General aspects . 7
8.2 Pretreatment of test piece . 8
8.3 Preparation for the test . 8
8.4 Pretest . 8
8.5 Test of acetaldehyde removal and CO conversion . 8
8.6 Test of acetaldehyde removal (when CO concentration cannot be measured). 9
9 Calculation .10
9.1 Calculation method .10
9.2 Removal percentage and removed quantity of acetaldehyde .11
9.3 Conversion to CO .11
10 Test method for test pieces with lower performance .12
11 Test report .12
Annex A (informative) Results of an interlaboratory test .14
Bibliography .16
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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
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 the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
A list of all parts in the ISO 17168 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.
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 17168-1 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
acetaldehyde, a representative lower aliphatic volatile organic compound (VOC), enabling swift
distribution of photocatalytic products and thus contributing to a safe and clean environment.
INTERNATIONAL STANDARD ISO 17168-2:2018(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for air-purification performance
of semiconducting photocatalytic materials under indoor
lighting environment —
Part 2:
Removal of acetaldehyde
1 Scope
This document specifies a test method for the determination of the air-purification performance, with
regards to removal of acetaldehyde, 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 4224, Ambient air — Determination of carbon monoxide — Non-dispersive infrared spectrometric method
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 air-flow rate converted into that at the standard state (0 °C and 101,3 kPa) (l/min)
ϕ acetaldehyde volume fraction at the reactor exit (µl/l)
A
ϕ acetaldehyde volume fraction at the reactor exit under dark conditions (µl/l)
AD
ϕ volume fraction of acetaldehyde in the test gas (µl/l)
A0
ϕ CO volume fraction generated by indoor-light irradiation (µl/l)
CO2 2
ϕ CO volume fraction at the reactor exit under indoor-light irradiation (µl/l)
CO2,L 2
ϕ CO volume fraction at the reactor exit under dark conditions (µl/l)
CO2,D 2
ϕ CO volume fraction in the dark before indoor-light irradiation (µl/l)
CO2,Dpost 2
ϕ CO volume fraction in the dark after indoor-light irradiation (µl/l)
CO2,Dpre 2
n quantity of acetaldehyde removed by the test piece (µmol)
A
n quantity of CO converted from acetaldehyde per hour (μmol/h)
CO2 2
R removal percentage, by test piece, of acetaldehyde (%)
A
R conversion from acetaldehyde to CO (%)
CO2 2
5 Principle
This document deals with the development, comparison, quality assurance, characterization, reliability
[1]
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. Acetaldehyde (CH CHO) is chosen as a typical volatile
[2]
organic compound (VOC) with lower molecular mass and offensive odour . The test piece, placed
in a flow-type photoreactor, is activated by indoor-light illumination, and adsorbs and oxidizes gas-
[3]
phase acetaldehyde to form carbon dioxide (CO ) and other oxidation products . The air-purification
performance is determined from the amount of acetaldehyde removed by the test piece (μmol). The
simple adsorption by the test piece (not due to photocatalysis) is evaluated by the tests in the dark.
However, some test pieces are very absorbent, and a stable volume fraction of acetaldehyde may not
be attained in the designated test time. The photocatalytic activity may depend on the physical and
chemical properties of pollutants, mainly due to the adsorption process involved. For a better evaluation
of the 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.
The results of an interlaboratory test are given in Annex A to demonstrate the validity of this test method.
2 © ISO 2018 – All rights reserved

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 a 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-volume fractions of pollutants are to be tested, the system shall be constructed
with materials of low adsorption and resistant to ultraviolet (UV) radiation. An example of a testing
system is shown in Figure 1.
Key
1 test gas supply 9 four-way valve
2 air compressor 10 photoreactor
3 air-purification system 11 test piece
4 standard gas (pollutant) 12 airtight optical window
5 pressure regulator with a gauge 13 light source
6 mass-flow controller 14 sharp cut-off filter
7 humidifier 15 analyser
8 gas mixer 16 vent
Figure 1 — A schematic of the testing equipment
6.2 Test gas supply
The test gas supply provides air polluted with model contaminant at a predetermined concentration,
temperature and humidity, and supplies it continuously to the photoreactor. It consists of flow
regulators, a humidifier, gas mixers and so on. The flow rate of each gas should be within 5 % of the
designated value, which is easily attained by using thermal mass-flow controllers with knowledge of
temperature and gas type at calibration in accordance with ISO 6145-7. The expression of gas flow rate
in this document is that converted to the standard state (0 °C, 101,3 kPa). Typical capacities of flow
controller for pollutant gas, dry air and wet air are 100, 1 000 and 1 000 ml/min, respectively. The
standard acetaldehyde gas before dilution, normally balanced with nitrogen in a cylinder, shall have a
volume fraction of 50 µl/l to 250 µl/l. Synthetic air (N + O , such as supplied in cylinders) shall be used
2 2
for dilution when the CO from acetaldehyde is also measured.
6.3 Photoreactor
The photoreactor holds a planar test piece within a 50 mm-wide trough, with its surface parallel to an
airtight optical window for photoirradiation. The reactor shall be fabricated from materials that adsorb
little test gas and withstand irradiation of near-UV light. The test piece shall be separated from the
window by a 5,0 mm ± 0,5 mm-thick air layer. The test gas shall pass only through the space between
the test piece and the window. This gap shall be accurately set up according to the thickness of the
test piece, for example by using height-adjusting plates with different thicknesses, as shown in Figure 2
a). When a filter-type material is tested, an alternative type of test-piece holder shall be used, which
holds the test piece while allowing the test gas to pass through the cells of the filter under illumination
[Figure 2 b)]. Quartz or borosilicate glass that absorbs minimal light at wavelengths longer than 300 nm
should be used for the window.

4 © ISO 2018 – All rights reserved

a) For flat test pieces
b) For filter-type test pieces
Test piece length Test piece width Air layer thickness
l l l
1 2 g
99,0 ± 1,0 mm 49,0 ± 1,0 mm 5,0 ± 0,5 mm
Key
1 test gas inlet 6 auxiliary plate
2 baffle 7 test piece (flat-type)
3 airtight optical window 8 test gas outlet
4 flow channel 9 test piece holder
5 height-adjusting plate 10 test piece (filter-type)
Figure 2 — Cross-sectional views of photoreactor
6.4 Light source
A cool white halophosphate fluorescent lamp and a UV sharp cut-off filter as specified in ISO 14605
shall be used. The test piece shall be illuminated uniformly through the window by the light source.
When testing honeycomb-form photocatalysts, the light source shall illuminate one face of the test
piece. A light source that requires warming up shall be equipped with a shutter. The distance between
the light source and the reactor shall be adjusted so that the illuminance at the test piece surface is
6 000 lx ± 300 lx. The illuminance along the length of the test piece shall also be constant within ± 5 %.
The illuminance shall be measured with an illuminance meter which conforms to ISO 14605. The
reactor and light source shall be shielded from external light. The parts around the light source, such
as luminaire and shielding device, shall have small reflectance, or
...