Formaldehyde (https://zh.wikipedia.org/wiki/%E7%94%B2%E9%86%9B) is the gas of colorless and sensory irritant effects, its main harm is done to the skin mucous membrane irritation, when the content of formaldehyde in room reaches to a certain concentration, people will feel a sense of discomfort. When the concentration of formaldehyde is greater than 0.08 mg/m³, it will cause eye irritation, throat discomfort or pain, chest tightness, asthma, dermatitis, and so on; in addition, it has the bad influences like mutagenicity, carcinogenicity. In the year of 2011, the National Toxicology Program of United States described formaldehyde as the "known human carcinogen".

 

Moreover, the decoration board, paint furniture and automotive accessories and decorative objects, etc., which carry the harmful gases of formaldehyde can cause all kinds of chronic respiratory diseases. In foreign, people have very strict standard on the formaldehyde content controlling. Recently, an export of wood products in Taizhou, Zhejiang is sent back by the foreign for the first time, because of the content of formaldehyde and volatile substances is beyond the standard. We say, if they would spary the tungsten trioxide photocatalyst coating on the surface of building materials or formaldehyde-containing substrate, such a problem should not occur. Of course, the manufacturer cutting off the source of formaldehyde pollution is the key.

 

The principle that photocatalyst removes formaldehyde from building materials is: when exposure to ultraviolet light, the hydroxyl ions on the surface of photocatalyst will be oxidized to the hole "hydroxyl radical" by the electronic holes, the hydroxyl radicals will grab electrons from other organic compounds (formaldehyde and various of volatile organic compounds), and the organic compounds which are taken away electrons will be degraded into smaller molecules (such as carbon dioxide and water ect.) due to the loss of electronic bonding ability. Compare to the formaldehyde remover, the photocatalytic decomposition will not generate subsequent harmful organic compounds, thus to avoid a secondary pollution.

 

In addition, since tungsten trioxide photocatalyst has a wider optical response band of visible light, it can effectively take advantage of visible light and artificial lighting in indoor, no longer depend on the sun's ultraviolet rays, therefore, they can also play a very good decomposition effect of the formaldehyde in the internal of cupboard which can not often be irradiated by the bright light. Thus, the photocatalyst is considering as the most ideal material for removing formaldehyde, because its safety, small energy consumption, safe and harmless of the final product (carbon dioxide and water), etc..