What is the purpose of fusible plugs in chlorine cylinders?

Fusible plugs in chlorine cylinders are safety devices designed to prevent explosive situations in the event of overheating. Their primary purpose is to provide a controlled means for the release of gas or liquid chlorine as a pressure-relief measure before the pressure inside the cylinder becomes dangerously high enough to cause an explosion. When exposed to excessive heat, the fusible plug melts, which allows the chlorine gas to escape in a safe manner and thus helps to maintain cylinder integrity while minimizing the risk of catastrophic failure.

Other choices relate to different functions but do not accurately capture the primary safety role of fusible plugs. For instance, preventing gas from escaping and maintaining pressure are actually contrary to the intention of the plugs. The indication of chlorine remaining in the cylinder is typically not a function of fusible plugs, which are intended purely for safety under extreme conditions.