When the photocatalyst, TiO2, captures ultraviolet light it forms activated oxygen from water or oxygen in the air. Because of its catalytic nature photocatalyst properties are not consumed during this chemical reaction. The treated surface regenerates its photo-catalytic effect by reacting with oxygen in the air. This process is similar to photosynthesis that plants use, in which the chlorophyll captures sunlight to turn water and carbon dioxide into oxygen and glucose. This process can revolutionize air qualities emitted by buildings. Photocatalytic treated surfaces break down any organic compound and other harmful substances back into its original chemical form of carbon dioxide (CO2) and water (H2O) creating a cleaner and safer indoor environment. The most notable properties of photocatalyst is undoubtedly the self-cleaning ability. The powerful self cleaning effect of photocatalyst is based on a 0.2 to 0.5 micron thin film of titanium dioxide (TiO2), which is a photo-catalyst material applied on the treated surface. Within 1-2 hours this thin film chemically bonds to the surface and starts to absorb ultraviolet ray in the sunlight or artificial light to react with water vapor to form a strong oxidizing agent known as the hydroxyl radical. By adding self-cleaning properties for building windows cleaning cycles can be significantly reduced and extended. Other additional benefits can also be realized, such as control of mildew and bacterial levels, thanks to optimized formulations and choice of photocatalytic TiO2. Titanium dioxide is a safe substance, which is harmless to humans. It has been approved by the food-testing laboratory of the United States Food and Drug Administration (FDA).