When air is forced through a duct system, which pressure is likely to decrease?

When air is forced through a duct system, static pressure is likely to decrease due to various factors such as friction and turbulence within the ductwork. As air moves, it encounters resistance against the duct surfaces, which leads to a drop in static pressure. This pressure is defined as the potential energy of the air within the duct system, and when that energy is converted into kinetic energy as the air accelerates, the static pressure decreases.

In contrast, velocity pressure, which is associated with the speed of the air flow, typically increases due to the same driving force of the air being forced through the system. Dynamic pressure is a term that refers to the energy per unit volume of the moving air and is directly related to velocity pressure; hence, this pressure does not inherently decrease during the system operation under the same conditions.

Therefore, in the context of a duct system experiencing airflow, it is the static pressure that is most directly affected and likely to decrease as the air travels through the duct, owing to the losses created by the system's resistance to flow.