For closed foam-water systems, how is foam concentration verified?

• A. By visual observation
• B. By flow tests at those two conditions
• C. By colorimetric test
• D. By manufacturer data sheet only

Answer: (B)

In a closed foam-water system, you’re testing that the foam concentrate is being blended with water at the correct proportion when the system is in use. The amount of foam concentrate delivered depends on flow rate and operating conditions, and those factors can shift as pumps start, valve positions change, or flow rates vary. Because of that, the most reliable way to confirm the delivered foam concentration is to perform flow tests at two specified flow conditions and measure the actual foam-concentration at the discharge. This direct, quantitative check shows whether the proportioning device maintains the intended ratio across the system’s operating range.

Visual observation isn’t dependable for determining concentration, and colorimetric tests, while possible in some contexts, don’t replace the need to verify performance under real operating conditions in a closed system. Relying solely on the manufacturer data sheet ignores field variables and operating realities, so it wouldn’t ensure the system actually delivers the correct concentration during a fire scenario.