With the upsizing of wafers and substrates, the scale of clean room factories in the semiconductor/LCD industry is also expanding. Capital investment is as high as ¥500 billion (US$5 billion), boosting the asset value significantly. To secure a stable supply, suspension of production due to fire must never happen. The INERGEN gas fire control equipment , which sprays gas over the entire building to reduce the oxygen concentration to less than 15%, has been developed and installed at some universities and corporations. It is not harmful to people because there is carbon dioxide (CO2) in the gas to prevent breathing difficulties . However, since the plant cost is enormous, it is suitable for relatively small facilities only. An efficient and low-cost system adopting Ar-CO2 gas has been newly developed for quickly extinguishing fires in large factories.