What is a common safety feature on propane tanks designed for operation?

The correct answer is the overfill prevention device (OPD). This safety feature is specifically designed to prevent propane tanks from being filled beyond their maximum capacity, which is crucial for preventing potential overpressure situations that can lead to leaks or hazardous conditions. The OPD operates by using a float mechanism that restricts the fill valve when the tank reaches a predetermined level, ensuring proper operation within safe limits.

In the context of propane safety, this feature is essential as it not only helps in preventing overfilling but also contributes to the overall safety of transporting and storing propane. The OPD is now a standard requirement for most propane tanks, emphasizing its importance in maintaining safe operational standards.

While other features like the pressure gauge, flow restrictor, and emergency shut-off switch enhance safety in various ways, they do not specifically address the critical concern of preventing the overfilling of tanks, which can lead to dangerous circumstances. Instead, they serve different purposes such as monitoring pressure levels, controlling the flow of propane, and allowing for rapid shutdown in emergencies, respectively.