Formaldehyde

Formaldehyde is a colorless, flammable gas at room temperature and has a strong odor. Exposure to formaldehyde may cause adverse health effects.

Sources

• resins used in the manufacture of composite wood products (i.e., hardwood plywood, particleboard and medium-density fiberboard)
• building materials and insulation
• household products such as glues, permanent press fabrics, paints and coatings, lacquers and finishes, and paper products

It is a byproduct of combustion and certain other natural processes, and so is also found in:

• combustion byproduct such as tobacco smoke and fuel-burning appliances (gas stoves, kerosene space heaters and fireplaces)

More facts about formaldehyde, here.