Formalin has other name alias formaldehyde, have chemical formula of HCHO. Formaldehyde is the simplest member of the class of organic compounds known as Aldehyde. At room temperature formaldehyde is an extremely reactive colorless gas with a suffocating odor. It is commonly solid as an aqueous solution called as formalin or in solid polymeric forms called as paraformaldehyde and trioxane. Formaldehyde often used as preservative agent, people often use on food that actually have poison properties and carcinogenic. Formalin is used in manufacture of dyes, in the production of synthetic resins, and as a preservative agent for biological specimens. In India formalin many use to sterilize media on cultivation mushroom. Before they spread the spawn into the media they sterilize the cultivation media using small amount of formalin that is diluted into the water. Media then dipped on this solution and then let it dry before spread the spawn. In Indonesia to buy formalin from shop is diffic