Which design feature describes flexible ducts?

Which design feature describes flexible ducts?

• A. A rigid metal tube with no insulation
• B. An insulated outer jacket surrounding a plastic film coil spring inner liner.
• C. A hollow plastic bag
• D. A solid stone shell

Answer: (B)

Flexible ductwork is built to bend and route airflow while still controlling heat transfer and keeping the air contained. The key is a structure that can flex without losing integrity: an inner liner through which the air travels, a supporting coil or spring to hold the shape, and insulation with an outer jacket to reduce heat loss and protect the liner. The correct description captures this setup—an insulated outer jacket surrounding a plastic film liner that’s kept in shape by a coil or spring—precisely how flexible ducts are designed. The other options describe rigid, non-insulated tubing, an unusable hollow bag, or an unrelated solid shell, which don’t match flexible duct construction.

Flexible ductwork is built to bend and route airflow while still controlling heat transfer and keeping the air contained. The key is a structure that can flex without losing integrity: an inner liner through which the air travels, a supporting coil or spring to hold the shape, and insulation with an outer jacket to reduce heat loss and protect the liner. The correct description captures this setup—an insulated outer jacket surrounding a plastic film liner that’s kept in shape by a coil or spring—precisely how flexible ducts are designed. The other options describe rigid, non-insulated tubing, an unusable hollow bag, or an unrelated solid shell, which don’t match flexible duct construction.