In a compressed air system, which unit is commonly used to quantify leak rate per unit time?

• A. PSI
• B. CFM (cubic feet per minute)
• C. J/s
• D. Pa

Answer: (B)

Leak rate is about how much air volume escapes each minute, i.e., a flow rate. In compressed air systems, that volume-per-time measure is commonly expressed as cubic feet per minute, or CFM, because it directly reflects how much air is being lost relative to the system’s capacity and energy use. Pressure units like PSI or Pa tell you how pressurized the air is, not how fast it’s leaking, and J/s denotes power, not volume flow. So expressing the leak rate in CFM provides a practical, comparable way to quantify and manage leaks.