For how long must water extinguishers discharge at least?

Water extinguishers are designed to effectively combat fires involving ordinary combustibles such as wood, paper, and textiles. The requirement for these extinguishers specifies a minimum discharge time to ensure that users have adequate time to tackle a fire effectively. A discharge time of at least 40 seconds is considered the standard minimum because it allows enough time for the operator to direct the water stream at the base of the fire and suppress the flames adequately.

A discharge time that meets or exceeds this minimum is critical to ensure the extinguishing agent is delivered effectively and can reach the seat of the fire. With a 40-second discharge time, it ensures that there’s sufficient capacity for getting closer to the fire while still allowing for safety measures.

This standard is also in line with safety codes and regulations, which dictate the performance characteristics necessary for various types of fire extinguishers, thereby ensuring they are fit for purpose in emergency situations. The other choices offer longer discharge times, which exceed the established minimum but do not constitute the minimum requirement for water extinguishers.