Which of the following items must be verified before conducting foam solution concentration tests?

The verification of the flushing of piping systems and the operational status of water and foam systems is essential before conducting foam solution concentration tests. This step ensures that the testing environment is not contaminated by residual substances from previous operations and that the water and foam delivery systems are functioning correctly. Contaminants could hinder accurate testing results or lead to incorrect concentrations of foam solution.

Additionally, confirming the operational status of the systems is critical because if the systems are improperly functioning or not primed correctly, the test results will be unreliable. A successful foam concentration test relies on the integrity and cleanliness of the equipment being used, making this verification necessary to ensure safety and effectiveness during actual firefighting operations. Thus, focusing on the flushing of the systems and the operational readiness of both water and foam systems is fundamental in preparing for accurate foam solution concentration tests.