Air flow testing of duct systems are important to assist the CFM being delivered and returned. The air handler is designed to deliver specific amount of CFM and receive back. Static pressures will reduce air flow. With every turn in a supply line restricts air flow as well. We test and balance air flow in commercial systems gauge the CFM. Incorrect flow or balancing is costing you money and efficiency. In many cases duct systems were designed and installed incorrectly. Either undersized or over sized. Dampers were not installed to control and balance air flow. In some cases duct board or flex material was used. These materials breakdown over time causing leakage, bad air and building pressure changes.
The air handler in your place of business is designed to deliver a measured amount of cubic feet per minute of air flow. When the system was first installed it was designed by how many square feet of space it was to heat and cool. Factored in was heat loads, windows, occupancy, R-value in walls and ceilings. Air handler air flow declines over the years due to several reasons. The fan "squirrel cage" that drives air flow becomes dirty over time, duct work is broken due to rodents or poor craftsmanship during install. The duct system designed was undersized in many cases. Or simply because the system's air flow was not tested after being commissioned.
The square feet of an office must receive required CFM to properly heat and cool. Under size or over size systems will not efficiently do its job. With proper balancing, if 250 CFM is delivered to an office then 250 CFM should be returned. Duct leakage and static pressures greatly reduce efficiency. With accurate testing by a trained professional can correct these issues.