Galvanized spiral duct refers to the air supply, exhaust, and smoke exhaust ducts used in hotels, shopping malls, textiles, chemical fibers, petrochemicals, machinery manufacturing, instrumentation, electronics, pharmaceuticals, tobacco, food, medical, warehousing, office buildings, as well as subway, civil air defense, basements, and other engineering projects. https://www.wsduct.com/galvanized-spiral-air-duct.html