Ducts (or conduits) offer a highly protective environment for fiber-optic cables. They are typically buried outside, and then the cables are air-blown, jetted, pulled, or pushed into the duct. Fiber optic cables for outdoor applications are engineered to withstand the more demanding conditions seen outside, from environmental extremes to mechanical forces. Each type is designed with specific features to ensure optimal performance under varying conditions. Indoor fiber optic cables are commonly used in buildings, offices. Fiber optic cable may be installed indoors or outdoors using several different installation processes. Outdoor cable may be direct buried, pulled or blown into conduit or innerduct, or installed aerially between poles. Indoor cables can be installed in raceways, cable trays above ceilings or under. A conduit is a protective tube or channel that houses the fiber optic cables, shielding them from moisture, dust, physical stress, and other environmental factors.