What does the term "static pressure" refer to in HVAC systems?

Static pressure in HVAC systems refers to the pressure exerted by the air within the ductwork when the air is stationary. It is a critical parameter for the proper functioning of the ventilation system, as it affects how air moves through ducts and how well it can reach various areas within a building.

Static pressure is often measured in inches of water column (in. WC) and is used to assess the resistance encountered by the airflow as it travels through ducts, alterations, and fittings. Understanding static pressure helps HVAC technicians diagnose issues related to airflow, such as blockages or duct design inefficiencies, which can significantly impact system performance and energy efficiency.

The other options refer to different aspects of HVAC systems; airflow is a measure of how much air is being moved, temperature relates to the thermal characteristics of the air, and velocity refers to the speed at which the air is traveling through the ducts. However, none of these concepts directly describe the pressure created by stationary air in the ducts, which is the essence of static pressure.