By far the most hazardous material chemically in the uranium fuel cycle is uranium hexafluoride (UF6). Uranium hexafluoride is an extremely dangerous material due to the compounds it forms when it reacts with moisture in the air. These compounds are hydrogen fluoride (HF) and uranyl fluoride (UO2F2). Both of these compounds are extremely toxic as well as corrosive. Being a gas the hazard of uranium hexafluoride is due to inhalation.