Colorless combustible gas, with a strong irritating, asphyxiating odor, human eyes, nose and other stimulating effects.
 

Formaldehyde is used as a tissue preservative in medical laboratories and as an embalming fluid in mortuaries. It is also used as a preservative in some foods and as an antibacterial ingredient in cosmetics, household antiseptics, medicines, dishwashing liquids, fabric softeners, carpet cleaners, lacquers, and wood products. It is used as a preservative in some paints, paper coatings, and cosmetics; in the permanent press coating on fabrics; in carpets; and in some foam insulation materials.
 

Formaldehyde (systematic name methanal) is a naturally occurring organic compound with the formula CH2O (H−CHO). It is the simplest of the aldehydes (R−CHO).
Formaldehyde is more complicated than many simple carbon compounds in that it adopts several different forms. As a gas, formaldehyde is colorless and has a characteristic pungent, irritating odor. Upon condensation, the gas converts to various other forms of formaldehyde (with different chemical formulas) that are of more practical value. One derivative is the cyclic trimer metaformaldehyde (1,3,5-trioxane) with the formula (CH2O)3. There is also a linear polymer called paraformaldehyde. These compounds have similar chemical properties and are often used interchangeably.

When dissolved in water, formaldehyde also forms a hydrate, methanediol, with the formula H2C(OH)2. This compound also exists in equilibrium with various oligomers (short polymers), depending on the concentration and temperature. A saturated water solution, of about 40% formaldehyde by volume or 37% by mass, is called "100% formalin". A small amount of stabilizer, such as methanol, is usually added to suppress oxidation and polymerization. A typical commercial grade formalin may contain 10-12% methanol in addition to various metallic impurities. "Formaldehyde" was first used as a generic trademark in 1893 following a previous trade name, "formalin".
 

We normally list 2 years as the shelf life in our COA, the real shelf life is actually much longer than 2 years if it's stocked in good condition (bags are sealed enough, away from direct sun-light, moisture and other incompatible chemical materials).