ISO/TC 206/WG 9 - Photocatalysis

This document specifies light emitting diodes (LED) for light source and radiometers used in the performance evaluation of semiconducting photocatalytic materials under indoor LED lighting environments in a laboratory. Light sources for indoor lighting environments do not include sunlight passing through window glass. This document does not replace ISO 14605.[1] Either document can apply depending on the lighting environment in which the photocatalytic material is used.

This document specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under irradiation with long-wave ultraviolet (UV) light. This document is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, that are the basic forms of materials for various applications. This document also applies to structured filter materials including honeycomb-form, woven and non-woven fabrics, and to plastic or paper materials if they contain ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the removal of formaldehyde.

This document specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under irradiation with long-wave ultraviolet (UV) light. This document is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, that are the basic forms of materials for various applications. This document also applies to structured filter materials including honeycomb-form, woven and non-woven fabrics, and to plastic or paper materials if they contain ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the removal of methyl mercaptan.

This document establishes a test method for determining the antibacterial activity of materials containing an indoor-light-active photocatalytic material on the surface. The antibacterial reduction rate is determined by measuring the survival of bacteria after illumination with indoor light. This test assumes a surface with high potential of possible person contact with bacteria. This test is designed to evaluate the suppression of contact infection of bacteria using an indoor-light-active photocatalytic material under indoor lighting environment. It is intended for use with different kinds of indoor-light-active photocatalytic materials used in construction, for example, flat sheets, board or plate shapes, which are the basic forms of materials for various applications. It is not applicable to powder, granular, or porous indoor-light-active photocatalytic materials, as well as cloths or textiles. It is applicable to indoor-light-active photocatalytic materials produced for antibacterial application. Other types of indoor-light-active photocatalytic materials applications, i.e. decomposition of water contaminants, self-cleaning, antifogging, and air purification, are non-applicable by this method.

This document specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under irradiation with ultraviolet light (UV-A). This document is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, that are the basic forms of materials for various applications. This document also applies to structured filter materials including honeycomb-form, woven and non-woven fabrics, and to plastic or paper materials if they contain ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the removal of acetaldehyde.

This document specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under irradiation with ultraviolet light (UV-A). This document is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, that are the basic forms of materials for various applications. This document also applies to structured filter materials including honeycomb-form, woven and non-woven fabrics, and to plastic or paper materials if they contain ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the removal of toluene.

This document provides a testing method for testing phenol oxidative decomposition performance of semiconducting photocatalytic materials or made of a material adsorbed with photocatalyst to its surface for the purpose of purifying water polluting substances in water making use of photocatalytic performance as test piece. The test piece can be planar, spherical, flake or block shape. A test piece that can elute hydrocarbon or the like by immersion into water or phenol aqueous solution or by light irradiation, a semiconducting photocatalytic material that cannot maintain its shape or a powdery semiconducting photocatalytic material are excluded from the scope of application, since they cannot be evaluated.

This document specifies a test method for the determination of the antibacterial activity of materials that contain a photocatalyst or have photocatalytic films on the surface, by measuring the enumeration of bacteria under irradiation of ultraviolet light. This document is intended for use with different kinds of semiconducting photocatalytic materials used in construction materials in flat sheet, board, plate shape or textiles that are the basic forms of materials for various applications. It does not include powder, granular or porous photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for antibacterial effect. Other types of performance of photocatalytic materials, i.e. antifungal activity, antiviral activity, decomposition of water contaminants, self-cleaning, antifogging and air purification, are not determined by this method. The values expressed in this document are in accordance with the International System of Units (SI).

This document specifies a test method for the determination of the air-purification performance, with regards to removal of methyl mercaptan, of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination with indoor light. This document is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, which are the basic forms of materials for various applications. This document also applies to materials in honeycomb form, and to plastic or paper materials containing ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions.

This document specifies a test method for the determination of the air-purification performance, with regards to the removal of toluene, of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination from indoor light. This document is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, which are the basic forms of materials for various applications. This document also applies to materials in honeycomb form, and to plastic or paper materials containing ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions.

This document specifies a test method for the determination of the air-purification performance, with regards to the removal of formaldehyde, of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination from indoor light. This document is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, which are the basic forms of materials for various applications. This document also applies to materials in honeycomb form, and to plastic or paper materials containing ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions.

This document specifies a method, the Resazurin (Rz) ink test, for the qualitative assessment of the activity of a photocatalytic surface, and its classification as below, within, or above the applicable range of the test. The method then allows for the subsequent semiquantitative evaluation of the activities of photocatalytic surfaces that are within the applicable range of the test. In all cases, artificial ultraviolet (UV) radiation is used. The test method specified is appropriate for use with all flat, smooth, photocatalytic surfaces, which are not macroporous, examples of which include: commercial photocatalytic glass, paint, tiles and awning materials. The method is not applicable to assessing the visible-light activity of photocatalytic surfaces, nor their ability to effect: air purification, water purification, self-cleaning or disinfection, although some relevant correlations have been reported[4][5].

This document specifies a test method for the determination of the air purification performance, with regards to removal of nitric oxide, of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination from indoor light. This document is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, which are the basic forms of materials for various applications. This document also applies to materials in honeycomb form and to plastic or paper materials containing ceramic microcrystals and composites. This document does not apply to certain test pieces that contain a large amount of adsorbent, due to unattained adsorption equilibrium. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions.

This document specifies a test method for the determination of the air-purification performance, with regards to removal of acetaldehyde, of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination from indoor light. This document is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, which are the basic forms of materials for various applications. This document also applies to materials in honeycomb form, and to plastic or paper materials containing ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions.

ISO 19652:2018 specifies a test method for the determination of complete decomposition performance of indoor light-active photocatalytic materials under an indoor lighting environment using acetaldehyde. In this document, photocatalytic materials are usually made from semiconducting metal oxides, such as titanium dioxide, tungsten trioxide or other ceramic materials, and they are treated in powder form. This document does not apply to film, flat sheet, board and other plate-shape materials. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions.

ISO 19722:2017 specifies the test method for determination of concentration of dissolved oxygen consumed due to photocatalytic oxidation of phenol in aqueous phase by semiconducting photocatalytic substances. The method is applicable to powder test sample or film test piece of semiconducting photocatalystic material targeting water contaminants. This test method is not applicable for evaluating the materials conjugated with other base material, such as organic binder which can also be decomposed by the photocatalytic activity. ISO 19722:2017 is applicable to the test method for the activity of powder test sample or film test piece of semiconducting photocatalystic material targeting water contaminants.

ISO 22197-1:2016 specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination with ultraviolet light. This document is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, that are the basic forms of materials for various applications. This document also applies to materials in honeycomb-form and to plastic or paper materials if they contain ceramic microcrystals and composites. This document does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the removal of nitric oxide.

ISO 18071:2016 specifies the determination of the antiviral activity of materials that contain indoor-light-active photocatalytic materials or have indoor-light-active photocatalytic films on the surface by a test method that measures the infectivity titre of bacteriophage Q-beta after illumination with indoor light. NOTE In the test method, the surrogate microbe is bacteriophage Q-beta, intended as a model for influenza viruses. It is intended for use with different kinds of indoor-light-active photocatalytic materials used in construction materials, in flat sheet, board or plate shape that are the basic forms of materials for various applications. It does not include powder, granular or porous indoor-light-active photocatalytic materials. It is applicable to indoor-light-active photocatalytic materials produced for an antiviral applications. Other types of performance of indoor-light-active photocatalytic materials, i.e. antibacterial activity, antifungal activity, decomposition of water contaminants, self-cleaning, antifogging and air purification, are not determined by this method.

ISO 19635:2016 specifies a test method for evaluating anti-algal activities in outdoor structures, specifically flat photocatalytic materials (for example, window panes and water tank glasses, films, guardrails, etc.) under irradiation of ultraviolet light. It does not include powder, granular or porous photocatalytic materials.

ISO 18560-1:2014 specifies a test method for the determination of the air-purification performance of materials that contain a indoor-light-active photocatalyst or have indoor-light-active photocatalytic films on the surface, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination with indoor light. Formaldehyde (HCHO) is chosen because it is a typical indoor air pollutant that causes the so-called sick building syndrome. This part of ISO 18560 is intended to evaluate the photocatalytic performance for building materials, such as boards, wallpapers. This part of ISO 18560 does not apply to powder or granular photocatalytic materials. This test method is usually applicable to indoor-light-active photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attribute of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. This test method is based on ISO 16000‑23 and is adjusted for the measurement of indoor-light-active photocatalytic materials. NOTE Another test method for the determination of air-purification performance of photocatalytic materials by using formaldehyde is described in ISO 22197‑4. The test methods comprising of ISO 22197 are prepared for evaluation of material-based air-purification performance under irradiation of ultraviolet light, while this part of ISO 18560 is intended for providing a direct index to the improvement of indoor air quality by the indoor-light-active photocatalytic materials under the simulated conditions. Approximate correlation between the results by ISO 22197‑4 and this part of ISO 18560 has been confirmed.

ISO 18061:2014 specifies a test method for the determination of the antiviral activity of materials that contain photocatalytic materials or have photocatalytic films on the surface, by enumerating the destruction of bacteriophage Q-beta after irradiation of ultraviolet light. It is intended for use with different kinds of semiconducting photocatalytic materials used in construction materials, in flat sheet, board, or plate shape that are the basic forms of materials for various applications. It does not include powder, granular, or porous photocatalytic materials. It is applicable to photocatalytic materials produced for an antiviral application. Other types of performance of photocatalytic materials, i.e. antibacterial activity, antifungal activity, decomposition of water contaminants, self-cleaning, antifogging, and air purification, are not determined by the test method.

ISO 17094:2014 presents a test method for determining the antibacterial activity of materials that contain an indoor-light-active photocatalytic material or have indoor-light-active photocatalytic films on the surface by measuring the survival of bacteria after illumination with indoor light. It is intended for use with different kinds of indoor-light-active photocatalytic materials used in construction materials in flat sheet, board or plate shape that are the basic forms of materials for various applications. It does not include powder, granular, or porous indoor-light-active photocatalytic materials, nor is it applicable to cloth or textiles. It is applicable to indoor-light-active photocatalytic materials produced for antibacterial application. Other types of performance of indoor-light-active photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging, and air purification, cannot be determined by this method.

ISO 14605:2013 specifies the light source and radiometer used in the performance evaluation of semiconducting photocatalytic materials used under an indoor lighting environment in a laboratory. A light source of an indoor lighting environment does not include the sunlight passing through the window glass.

ISO 13125:2013 specifies a test method covering the determination of the antifungal activity of materials that contain a photocatalyst or have photocatalytic films on their surface, by counting the number of pre-incubated fungal spores that survive exposure to ultraviolet (UV-A) light. ISO 13125:2013 provides for the assessment of different kinds on materials used in various applications, such as construction materials in flat coating, sheet, board or plate form, etc. Powder, granular, fibrous or porous photocatalytic materials are not included. Values expressed in ISO 13125:2013 are in accordance with the International System of Units (SI).

ISO 10677:2011 describes an ultraviolet (UV) light source and specifies a method of measuring the radiation intensity which is used in testing the performance of semiconducting photocatalytic materials in a laboratory.

ISO 10676:2010 describes a test method covering photocatalytic materials formed on, or attached to, another material surface for the purpose of decomposing, and thus eliminating, the pollutants in water, using photocatalytic performance. This test method is applicable to photocatalytic materials under UV irradiation, and not under visible light irradiation.

ISO 10678:2010 specifies a method for the determination of the photocatalytic activity of surfaces by degradation of the dye molecule methylene blue (MB) in aqueous solution using artificial ultraviolet (UV) radiation, and characterizes the ability of photoactive surfaces to degrade dissolved organic molecules on ultraviolet radiation. The test method specified is also applicable to evaluation of the specific photocatalytic self-cleaning activity of surfaces covered with respective coatings. This method is not applicable to characterizing the photoactivity of surfaces on visible illumination, regarding direct soiling, degradation of gaseous molecules and the determination of antimicrobial photoactivity of surfaces.

ISO 27448:2009 deals with fine ceramics. ISO 27448:2009 specifies a test method for the determination of the self-cleaning performance of materials that contain a photocatalyst or have photocatalytic films on the surface, and which are usually made from semiconducting metal oxides such as titanium dioxide. This method is used to measure the water contact angle under illumination with ultraviolet light, which is one of the indices influencing the self-cleaning performance of photocatalytic materials. ISO 27448:2009 does not include water-permeable substrates, rough surfaces which do not have exposed water droplets, highly hydrophobic, powder or granular materials, or visible light-sensitive photocatalysts.

ISO 19810:2017 specifies a test method for the determination of the self-cleaning performance of sheet-form materials that contain an indoor-light-active photocatalyst or have indoor-light-active photocatalytic films on the surface, under indoor lighting environment. This method is used to measure the change of water contact angle under indoor lighting environment, which is one of the indices reflecting the self-cleaning performance of semiconducting photocatalytic materials. ISO 19810:2017 is not applicable to permeable materials on which water droplets cannot hold and rough materials which obscure water droplets. This document is not applicable to materials of which the changes in the water contact angle due to decomposition of adhered organic matter cannot be evaluated because even if the surface is clean the water contact angle is remarkably large or the water contact angle cannot be sufficiently increased by attaching organic matter to the surface.

ISO 22197-5:2013 specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination with ultraviolet light (UV-A). ISO 22197-5:2013 is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, that are the basic forms of materials for various applications. ISO 22197-5:2013 also applies to structured filter materials including honeycomb-form, woven and non-woven fabrics, and to plastic or paper materials if they contain ceramic microcrystals and composites. ISO 22197-5:2013 does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the removal of methyl mercaptan.

ISO 22197-4:2013 specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination with ultraviolet light (UV-A). ISO 22197-4:2013 is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, that are the basic forms of materials for various applications. ISO 22197-4:2013 also applies to structured filter materials including honeycomb-form, woven and non-woven fabrics, and to plastic or paper materials if they contain ceramic microcrystals and composites. ISO 22197-4:2013 does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the removal of formaldehyde.

ISO 22197-2:2011 specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination with ultraviolet light (UV-A). ISO 22197-2:2011 is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, that are the basic forms of materials for various applications. ISO 22197-2:2011 also applies to structured filter materials including honeycomb-form, woven and non-woven fabrics, and to plastic or paper materials if they contain ceramic microcrystals and composites. ISO 22197-2:2011 does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the removal of acetaldehyde.

ISO 22197-3:2011 specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination with ultraviolet light (UV-A). ISO 22197-3:2011 is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, that are the basic forms of materials for various applications. ISO 22197-3:2011 also applies to structured filter materials including honeycomb-form, woven and non-oven fabrics, and to plastic or paper materials if they contain ceramic microcrystals and composites. ISO 22197-3:2011 does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the removal of toluene.

ISO 27447:2009 specifies a test method for the determination of the antibacterial activity of materials that contain a photocatalyst or have photocatalytic films on the surface, by measuring the enumeration of bacteria under irradiation of ultraviolet light. ISO 27447:2009 is intended for use with different kinds of semiconducting photocatalytic materials used in construction materials, in flat sheet, board, plate shape or textiles that are the basic forms of materials for various applications. It does not include powder, granular or porous photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for an antibacterial effect. Other types of performance of photocatalytic materials, i.e. decomposition of water contaminants, self-cleaning, antifogging and air purification, are not determined by this method. The values expressed in ISO 27447:2009 are in accordance with the International System of Units (SI).

ISO 22197 -1:2007 specifies a test method for the determination of the air-purification performance of materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of a test piece to the model air pollutant under illumination with ultraviolet light. ISO 22197 -1:2007 is intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate shape, that are the basic forms of materials for various applications. ISO 22197 -1:2007 also applies to materials in honeycomb-form, and to plastic or paper materials if they contain ceramic microcrystals and composites. ISO 22197 -1:2007 does not apply to powder or granular photocatalytic materials. This test method is usually applicable to photocatalytic materials produced for air purification. This method is not suitable for the determination of other performance attributes of photocatalytic materials, i.e., decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the removal of nitric oxide.