Formaldehyde is an organic compound with the formula CH₂O and structure H−CHO. The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as aqueous solutions, which consists mainly of the hydrate CH₂₂. It is the simplest of the aldehydes. As a precursor to many other materials and chemical compounds, in 2006 the global production of formaldehyde was estimated at 12 million tons per year. It is mainly used in the production of industrial resins, e.g., for particle board and coatings.