How are fan airflow pressures typically measured?

Fan airflow pressures are typically measured in inches of water column (WC) because this unit provides a clear measure of pressure in a fluid system, specifically air in this context. The measurement in inches of water column reflects the pressure differential created by fans, which relates to how effectively they can move air through a system.

When assessing airflow in HVAC systems, pressure measurements are crucial for determining how well air is being circulated and whether it meets design specifications. Inches of water column specifically helps quantify the airflow pressures as they relate to the resistance air encounters, allowing engineers and technicians to adjust systems appropriately to ensure efficient operation.

Other units listed do not apply to airflow pressure measurements in the same context. For example, pounds per square inch (psi) is a standard unit for measuring pressure but is generally used for gases and liquids under higher pressure scenarios, not specifically airflow in HVAC applications. Gallons per minute (GPM) measures flow rate, typically of liquids, while cubic feet per minute (CFM) measures the volume of airflow, not pressure. Hence, the correct choice reflects the most relevant unit for measuring the pressures related to fan airflow.