You have heard of Formalin immersed in which the biological samples are kept? It is nothing but Formaldehyde diluted in water. It is used as an embalming agent in Biological Specimen and is one of the best preservatives. read more
In Paints, Plastics and Adhesives for wood and plywood, Resins of Urea Formaldehyde, Phenol Formaldehyde, and Melamine Formaldehyde are extensively used. Formaldehyde was earlier used in Emulsion Paints and Water thinnable Paints, for prevention of infection and growth in microorganisms. read more
For the record, formaldehyde shows up in only one group of finishes we woodworkers use: the so-called catalyzed and pre-cat lacquers and conversion varnishes. It is not in shellac, lacquer, oil varnish, water-based lacquers, oil- or water-based polyurethane or even two-part automotive polyurethanes or polyesters. read more