ISO 27447-Antibacterial activity of semiconducting photocatalytic materialsISO 27447: 2019.

Accredited by ENAC (National Accreditation Entity)

This standard determines the activity and antimicrobial efficacy of photocatalytic products containing materials or photocatalytic films on its surface causing oxidation and reduction reactions under the action of ultraviolet radiation. For this, the reduction in the number of various species of bacteria deposited as inoculum at the surface of the test material is assayed. There are two ways test: method covering with a glass sheet once inoculated test material with the bacterial suspensions intended for testing fabrics and textile products, and a method covering with adhesive transparent sheet intended for testing flat sheets, boards and other materials with flat surface. The method of covering with glass sheet use Staphylococcus aureus and Klebsiella pneumoniae, and the method of covering with transparent adhesive film use Staphylococcus aureus and Escherichia coli. In both methods, the test material is placed inside a petri dish base on a carrier, it is inoculated with a bacterial suspension (0.2 mL 1 x 10^5 cells / mL for method glass sheet, and 0.15 mL with 6.7 x 10^5 to 2.6 x 10^6 cells/mL for the adherent film method). In both methods of test pieces 50 mm +/- 2 mm x 50 +/- 2 mm x 10 mm thickness are used. The number of test pieces is 15, designed in groups of 3 without photocatalytic product units to quantify the inoculum control; 3 photocatalytic product units and other units without photocatalytic product 3 to keep in the same test chamber without exposure to UV radiation; and 3 units photocatalytic product and other three units without photocatalytic product to keep in the same test chamber with ultraviolet radiation exposure. Once made the exposure of the test material inocula and radiation existing in each of the surfaces, bacteria are quantitated by comparing the number of bacteria in the surfaces exposed to ultraviolet radiation compared to the inoculated surfaces but not exposed to ultraviolet radiation. For this count the bacteria should be collected from each surface (total 15 for each bacteria), perform five dilutions at base 10, and make the seeding of each dilution in duplicate (in total 300 cultures: 15 samples of test x 2 bacteria x 5 x dilutions to count duplicate cultures). The number of pieces of material would be at least 30 (15 x 2 bacteria), 18 of them without active ingredient, and 12 with the test product, although it would be necessary to receive 60 (36 without the product and with the same type of + 24 finish with the product) to have enough in case be necessary to repeat any step of the test. The customer must specify the circumstances where materials are used, to irradiate the material with an intensity of ultraviolet radiation or another.
 
UV intensity Example
0.25 mW / cm2 * By the window during the day along the lamp for the photocatalytic reaction (eg BLB)
0.10 mW / cm2 In the room (within about 1.5 m away from the window) during the day, out the window early in the morning or before sunset
0.01 mW / cm2 In the room (inside, about 3 meters from the window) during the day
0,001 mW / cm2 In the windowless room (interior light only) in the room at night (interior light only).

 

The time of exposure to ultraviolet light can be 4 to 8 hours, so that the applicant must choose it as what are the conditional use.