Formaldehyde ( for-MAL-di-hide, fər-) (systematic name methanal) is an organic compound with the chemical formula CH2O and structure H2C=O. It is a pungent, colorless gas that spontaneously polymerizes into paraformaldehyde. It is stored as a ~37% aqueous solution (formalin), which consists mainly of the hydrate CH2(OH)2. It is the simplest of the aldehydes (R−CHO). As a precursor to many other materials and chemical compounds, in 2024 the global production of formaldehyde was estimated at 26 million tons per year. It is mainly used in the production of industrial resins, e.g., for particle board and coatings, plastics, pulp, paper, synthetic fibers, and textiles. A ~5% solution of formaldehyde is used as a disinfectant and fumigant in industrial, agricultural, and healthcare settings, and formalin is used to preserve tissue samples.