What unit is used to express the minimum flow for an initial attack line under NFPA 1410?

• A. Liters per minute (lpm)
• B. Gallons per second (gps)
• C. Gallons per minute (gpm)
• D. Liters per hour (lph)

Answer: (C)

Flow rate is what matters for an initial attack, and NFPA 1410 specifies that this rate be expressed in gallons per minute. Using gallons per minute aligns with how pump discharge, nozzle performance, and hose friction losses are routinely calculated in fireground operations in the U.S., making it the practical and standard unit for describing the minimum line flow. Other units aren’t used in this standard because they don’t match how firefighting equipment delivers water: liters per minute would be used in metric contexts, gallons per second would be an unnecessarily fine rate for typical fireground calculations, and liters per hour measures total volume over time rather than the delivery rate. Therefore, the correct unit is gallons per minute.