Urea Formaldehyde Foam Insulation

An effective insulating material that can be injected into a wall through a small opening. The foam expands within the cavity to fill it. However, the insulation may release formaldehyde gas, which may be hazardous.
Example: Testing kits are available to sense the presence of urea formaldehyde foam insulation. Once thought to be an effective product, it became known as "shrink and stink" and is now generally considered undesirable. At one time it was banned for use in homes and schools, but the ban was lifted because assertions of health threats were not proved.