The general area related to water supply, drainage, cold and hot air supply and purification. A variety of valves and fittings are used. Anti-rust measures must be taken for valves made of metals while containment treatment is necessary for those made of copper-based materials. Valves and fittings are used for Air-conditioner air ducts and hot and cold plumbing. The facilities that control temperature, humidity, volume, velocity, and purity of the air indoors.