ISO 17721-2:2021

Overview - ISO 17721-2:2021 (antibacterial activity of ceramic tile surfaces)

ISO 17721-2:2021 specifies quantitative test methods for evaluating the antibacterial activity of glazed and unglazed ceramic tile surfaces that have incorporated photocatalytic antibacterial agents. The standard defines how to prepare test specimens, inoculate with bacteria, apply UV irradiation (photocatalytic activation) or dark conditions, recover and enumerate survivors, and report validated antibacterial activity results. Results are tied to the specific experimental conditions used and do not imply performance in other environments.

Key topics and technical requirements

• Scope and limits: Applies only to ceramic tiles with incorporated photocatalytic agents. It does not cover secondary effects (chemical resistance, stain resistance, colour differences) or other photocatalytic performances (self‑cleaning, air purification, water contaminant decomposition).
• Test organisms: Standard test bacteria include Escherichia coli and Staphylococcus aureus (specified culture collections). Other strains may be documented if used.
• Specimen preparation: Typical specimen size ~ (50 ± 2) mm × (50 ± 2) mm; six treated specimens are required for a full test. All surfaces must be sterilized before testing.
• Materials and media: Specifies microbiological media and solutions (e.g., nutrient broth, 1/500 nutrient broth, nutrient agar, SCDLP, PBS) and a non‑ionic surfactant (polysorbate 80). Water quality and reagent grade requirements are specified.
• Procedure elements: Preparation of inoculum, use of adhesive film to confine inoculum, inoculation technique, UV irradiation conditions for photocatalytic activation, dark controls, recovery of bacteria and viable count enumeration.
• Validation and calculation: Test validity criteria, calculation of antibacterial activity values and required reporting details are defined to ensure comparability and reproducibility.
• Safety and competence: Emphasises trained personnel and appropriate microbiological laboratory practices.

Applications - who uses this standard

• Ceramic tile manufacturers evaluating or claiming antibacterial performance of tiles with photocatalytic additives.
• Quality assurance and R&D teams developing photocatalytic tile formulations and verifying efficacy.
• Test laboratories performing standardized antibacterial testing under controlled, reproducible conditions.
• Specifiers and procurement professionals who require validated antibacterial performance data for healthcare, food processing, public buildings or sanitary environments.

Related standards

• ISO 17721-1: Quantitative determination of antibacterial activity - Part 1 (general/other incorporated antibacterial agents)
• ISO 10545 series for ceramic tile properties (see ISO 10545-13 for chemical resistance, ISO 10545-14 for stain resistance, ISO 10545-16 for colour differences)

ISO 17721-2:2021 is essential when assessing photocatalytic antibacterial claims on ceramic tiles; results are meaningful only within the tested experimental conditions (temperature, humidity, bacterial species and nutrient state can all influence performance).