ISO 13125: 2013. Fine ceramics (advanced ceramics, advanced technical ceramics). Test method for antifungal activity of semiconducting photocatalytic materials.

Test accredited by ENAC (Spanish National Accreditation Entity).

This standard describes a test method for determining the antifungal activity of materials containing a photocatalyst or having a photocatalytic film on its surface. To evaluate the antifungal activity both the material subjected to the test, and the controls are covered with a suspension containing a known number of fungal spores and exposed to ultraviolet radiation. Subsequently, the number of spores that survive the exposure with ultraviolet radiation is detected.

The standard allows the evaluation of various kinds of materials for various applications in construction, such as flat coatings, sheets, boards or plates. Photocatalytic powdery, granular, fibrous or porous materials are not included in the evaluation.

In the test, the suspension of fungal spores is placed on the test pieces treated with photocatalytic and exposed to photoirradiation. After irradiation, the fungal spores are recovered and cultured in a suitable solid medium, which is incubated to allow the development of fungal colonies from spores that have survived. Subsequently, the number of surviving spores is analyzed by counting colonies developed in culture.

The antifungal activity of the photocatalytic reaction is estimated by calculating the decrease in the number of surviving spores in the sample of the photocatalytic test material, comparing it with what happened in the control of surfaces of the same material that does not contain the photocatalytic treatment.

This standard is an adaptation of the methodological concept of ISO 27447 for bactericidal activity (accredited in our laboratory), using the same devices, parts, a procedure and calculation of similar results, so it is recommended to use that standard as reference.

The standard indicates that spores of two fungal species are used to perform the test: Aspergillus niger (currently named Aspergillus brasiliensis) and Penicillium pinophilum. All tests are carried out at 25ºC ± 5ºC. The exposure time is a minimum of 3 hours and a maximum of 24 hours. The intensity of the exposure is 0.4 and 0.8 mW / cm2.

In the test, pieces of 50 mm ± 2 mm on each side and a maximum of 10 mm in thickness are used. In total, 6 pieces treated with the photocatalytic material and 9 similar pieces without photocatalytic material are required. If it is not possible to have untreated parts, the manufacturer can justify it and supply glass pieces similar in size. If it is not possible to have pieces of the aforementioned size it would be acceptable to use other sizes provided that their surface can be covered with sheets of 400 mm2 to 1600 mm2. The 15 pieces cited, 3 of the treated and 3 of the untreated are used to be irradiated once covered by the suspension of fungal spores. Other 3 pieces treated and other 3 pieces not treated are used as controls not exposed to radiation (kept in darkness). Another 3 untreated pieces are used in the survival control test of the fungal spores after their inoculation. However, should it be necessary to repeat any part of the test, it is recommended to send twice as many pieces of the indicated number, that is, 30 pieces (12 with photocatalytic treatment and 18 without photocatalytic treatment).