Toluene diisocyanate (TDI), 〖(OCN)〗_2 C_(6 ) H_3 〖CH〗_3, is water-white to pale-yellow liquid with a sharp pungent odor. It reacts with water to release carbon dioxide. The specific gravity is 1.22 which is heavier than water. TDI is toxic by inhalation and ingestion and is a strong irritant to skin and other tissue particularly the eyes. The TLV is 0.005 ppm in air and the IDLH is 10 ppm. The target organs are the respiratory system and the skin. The four-digit UN identification number is 2078. The NFPA 704 designation is health 3 flammability 1 and reactivity 3. The white section at the bottom of the diamond has with a slash through it indicating water reactivity. The primary uses of TDI are in the manufacture of polyurethane foams elastomers and coatings. The structure and molecular formula for TDI are shown in Figure 8.17.