What is a necessary condition for the safe use of flexible connectors?

The safe use of flexible connectors is primarily dependent on how they are installed. When flexible connectors are installed properly, it ensures that there is no undue strain on the connections that could lead to failures or leaks. Proper installation allows for movement and vibration absorption without putting excessive force on the joints or fittings. This is critical in maintaining a safe and reliable gas system, as any strain or misalignment can compromise the integrity of the connections and pose safety hazards.

Other options, while they may have importance, do not address the primary safety consideration for flexible connectors. For instance, using non-combustible materials or painting connectors for corrosion prevention may provide benefits but do not directly influence the installation process. Similarly, replacing connectors every year without context does not inherently ensure safety and could lead to unnecessary waste and costs, as the actual condition of the connectors should dictate the need for replacement.