What is the term for the distance an airstream travels where its velocity falls below a specified terminal level?

The term for the distance an airstream travels where its velocity falls below a specified terminal level is referred to as "throw." This concept is crucial in air distribution systems, particularly in determining how far air can be effectively delivered from a diffuser, grille, or register before its velocity decreases to a level that is no longer adequate for proper circulation or comfort.

Understanding throw is essential for HVAC professionals as it influences the design and placement of air distribution devices to ensure that conditioned air reaches all areas of a room efficiently. The distance of throw is affected by factors such as the supply air temperature, the velocity of the air exiting the diffuser, and the configuration of the space being conditioned.

Other terms, such as drop, velocity zone, or draft, do not accurately describe this specific phenomenon of distance traveled by air before its velocity diminishes.