Nihon Dempa Kogyo  Nihon Dempa Kogyo Co., Ltd. or is one of the world's largest quartz crystal companies, based in Shibuya, Tokyo, Japan. Using its synthetic quartz crystals, NDK produces crystal-related products such as crystal devices (e.g. crystal units, crystal oscillators, crystal filters) and ultrasonic transducers for medical use. In recent years, the company has begun to develop frequency synthesizers and low-power wireless modules. Nihon Dempa Kogyo has developed a prototype crystal-based disease detector which diagnoses disease from breath. The system works by detecting trace amounts of odor-causing substances found in a person's breath. NDK has sales offices in Japan, China, France, Germany, Italy, Malaysia, Singapore, United Kingdom, and United States. NDK has production and engineering facilities in Japan, China, Germany, Malaysia, and the United States. NDK's Belvidere, Illinois facility was heavily damaged in 2009 when one of the crystal autoclaves ruptured violently, causing an explosion. A beam from the NDK building killed a man at a nearby gas station, and a shard of the ruptured autoclave's wall injured two others and caused heavy damage in a nearby office building. The rupture was in a crystal-growth autoclave that had undergone stress corrosion cracking and was inadequately inspected; recommendations from a previous incident were ignored. As a result, the autoclave became overstressed and failed completely. Demolition of the facility began in March 2015.