The content of water vapor of gift wraping environment can also influence zip lock bag product quality, especially to pharmaceutical and precise electronic components. Water vapor is the medium of chemical printed bag reaction. On the one hand, the extremely big humidity can cause chemical to absorb moisture and subsequently result in deliquescence, dilution, decomposition, mildew, and distortion of drugs. On the other hand, the too small humidity will accelerate the efflorescence of medicines. Medicine is a kind of special gift wraping product, the quality of which must be secured within quality guarantee period. Therefore, materials with excellent barrier property must be used in their zip lock bag package.The preservation of different gift wraping products also varies in their requirements. For example, the content of carbon dioxide should be controlled in the zip lock bag packing of carbonic acid drink. Therefore, there are certain requirements for carbon dioxide permeability through such packing materials. When optimal preservation condition of product is determined according to their specific characteristics, corresponding packing method and packing materials can be selected to prolong quality guaranteed period of products to the maximum extent. In some cases where quality guarantee period is decided by market requirement, barrier property of material can be reversely calculated to design reasonable printed bag packaging structure so as to save packaging. http://www.niceindustry.co.uk/about.asp