Spiral duct refers to a type of HVAC (Heating, Ventilation, and Air Conditioning) ductwork that is constructed in a spiral shape. Instead of being rectangular or square like traditional ducts, spiral ducts are cylindrical and are typically made from metal such as galvanized steel or aluminum.

The main advantages of spiral ducts include:

1. Efficiency: Spiral ducts have smooth interiors that reduce air resistance, allowing air to flow more efficiently compared to rectangular ducts. This can lead to energy savings.
2. Installation: They are easier and quicker to install compared to rectangular ducts, as they often require fewer joints and fittings.
3. Durability: Made from metal, spiral ducts are durable and resistant to damage, ensuring a longer lifespan.
4. Aesthetic Appeal: Some consider spiral ducts to have a more modern and attractive appearance compared to traditional ductwork.
5. Maintenance: They are easier to clean and maintain due to their smooth surface and fewer joints.

Spiral ducts are commonly used in commercial and industrial HVAC systems where efficient airflow, durability, and ease of installation are important considerations.