In what unit are duct air pressures typically expressed?

Duct air pressures are typically expressed in inches of water gauge because this measurement accurately reflects the small pressures found in HVAC systems. The inches of water gauge allows for the representation of low-pressure differences effectively, which is essential for understanding airflow and performance in ducts.

This unit provides an appropriate scale for the pressures that are common in ventilation systems, where slight variations can have significant impacts on system efficiency and air distribution. Additionally, this unit is sensitive enough to measure the modest pressure changes that occur, making it the preferred choice in the HVAC industry.

Other units such as Pascals, inches of mercury, or pounds per square inch are either too broad or too large for the specific pressure ranges typically encountered in ductwork, thereby making inches of water gauge the most relevant and practical choice.