What must be present for a dry chemical extinguishing system to function properly during and after use?

For a dry chemical extinguishing system to function properly during and after use, it is essential to have a method to blow out all system piping. This practice ensures that any residual dry chemical left in the system is cleared effectively, allowing the system to reset and be ready for future use. Proper maintenance and the ability to clear out any blockages or leftover agents are critical to maintaining the reliability and functionality of the extinguishing system.

Clear piping is particularly important because any clogs or blockages can prevent the system from discharging properly in the event of a fire, which could lead to catastrophic failures. Ensuring that the system is clean and fully operational after use helps in maintaining its efficacy and compliance with safety standards.

The other options, while they may serve important roles in various other systems or scenarios, do not specifically address the fundamental requirement of ensuring the system is clear and functional post-use, which is crucial for the continued efficacy of a dry chemical extinguishing system.