ISO 22197-4:2021

Overview

ISO 22197-4:2021 specifies a laboratory test method for evaluating air‑purification performance of semiconducting photocatalytic materials with respect to the removal of formaldehyde. The standard covers materials that contain or are coated with photocatalysts (typically semiconducting metal oxides such as titanium dioxide), including flat construction panels, honeycomb and filter structures, woven/non‑woven fabrics, and composite plastics or papers that incorporate ceramic microcrystals. It is a flow‑type photoreactor test under long‑wave UV irradiation (300–400 nm) and quantifies formaldehyde removal as the net amount oxidized by the test piece.

Key topics and technical requirements

• Scope and exclusions: Applies to planar and structured materials (not to powder or granular photocatalysts) and is specific to formaldehyde removal (not for water contaminant degradation, self‑cleaning, antifogging or antibacterial properties).
• Photoreactor design: Test piece placed parallel to an optical window with an air gap of 5.0 mm ± 0.5 mm; typical flat test piece dimensions are about 99.0 mm × 49.0 mm. Filter‑type holders are provided for through‑flow materials.
• Light source and irradiance: UV source (BL/BLB per ISO 10677) in the 300–400 nm range; irradiance at the sample surface set to 10 W/m² ± 0.5 W/m² (uniformity ±5%).
• Test gas and flow control: Continuous supply of model test gas (formaldehyde) prepared from a standard cylinder (≈20 µl/l) or zero‑calibration air; flow rates are reported at standard state (0 °C, 101.3 kPa) and controlled within ±5% using mass‑flow controllers. Typical controller capacities and humidification equipment are specified.
• Sampling and analysis: Formaldehyde concentration is measured using active sampling methods referenced to ISO 16000‑3; adsorption is assessed by dark‑condition tests and photocatalytic removal by UV‑irradiated tests.
• Quality & reporting: Procedures for pretreatment, pretest, removal test, calculations (removal quantity in µmol and removal percentage) and reporting are defined to support reproducible performance comparisons.

Applications and users

ISO 22197-4 is used by:

• Materials and coatings manufacturers (photocatalytic tiles, panels, filters) for product development and quality control.
• Independent testing laboratories and certification bodies validating air‑purification claims.
• Indoor air quality specialists, architects and building product specifiers assessing materials for formaldehyde mitigation.
• R&D teams studying photocatalytic formulations and reactor designs.

Keywords: ISO 22197-4, photocatalytic materials, formaldehyde removal, air purification performance, photoreactor, titanium dioxide, UV irradiation, fine ceramics.

Related standards

• ISO 22197 series (other pollutant test methods)
• ISO 10677 (UV light source for photocatalyst testing)
• ISO 16000-3 (formaldehyde sampling and analysis)
• ISO/IEC 17025 (laboratory competence)