When zones need to be maintained at a certain pressure with respect to adjacent areas, we can employ two methods of determining these pressures, the absolute pressure method and the relative pressure method. The relative pressure method utilizes a NUCON model PD-C Pressure Detector and measures the relative differential pressure between zones and is useful for large zones or applications where pressures change quickly. The absolute pressure method utilizes two or more absolute pressure gauges and is often used in simpler zones, or zones where portable equipment is not feasible.
