ISO 17168-4:2018

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.