Methyl hydrazine, CH3NHNH2, is a colorless, hygroscopic liquid with an ammonia-like odor. It is soluble in water, with a specific gravity of 0.87, which is lighter than water. Methyl hydrazine is toxic by inhalation and ingestion, and is a suspected human carcinogen. The TLV ceiling is 0.2 ppm in air, and the IDLH is 50 ppm. The target organs are the central nervous system, respiratory system, liver, blood, eyes, and cardiovascular system. The four-digit UN identification number is 1244. The NFPA 704 designation is health 4, flammability 3, and reactivity 2. The primary uses are as a missile propellant and a solvent.