What is the definition of a PD HVAC? PD HVAC stands for Pressure Dependent Heating, Ventilation, and Air Conditioning. It is a system that is designed to regulate the amount of pressure within an enclosed space, usually a building. This type of system is typically used in industrial settings, as the fluctuations in pressure can be used to trigger certain processes. Pressure Dependent HVAC systems are composed of multiple components, such as ductwork, fans, and filters. The main purpose of a PD HVAC is to maintain a certain pressure level within the building. This is accomplished by the use of pressure sensors that detect any changes in pressure within the building and adjust the air flow accordingly. This ensures that the building remains pressurized, which helps to maintain the desired temperature. Additionally, PD HVACHVAC systems are designed with safety features, such as pressure relief valves, to protect the building from significant pressure fluctuations. In essence, PD HVACHVAC systems