What type of safety control must be used that will shut off the flow of gas in case of current failure?

A fail-safe type safety control is essential in gas systems because it is designed to automatically shut off the gas flow in the event of a current failure. This mechanism is crucial for preventing potentially hazardous situations, such as gas leaks, that could arise from a loss of power or failure in the system.

The fail-safe design ensures that when power is lost, the control system defaults to a safe condition, stopping the flow of gas. This proactive approach enhances safety by minimizing the risk of accidents that could lead to explosions or fires caused by unmonitored gas leaks.

In contrast, other types of safety controls such as manual shutoff or emergency valves require human intervention to operate or are not specifically designed to react to current failures automatically. An automatic regulator, while important for pressure regulation, does not provide the specific safety feature needed to react to a power loss by shutting off gas flow. Thus, the fail-safe type control stands out as the most appropriate choice for safeguarding against the hazards associated with current failures in gas supply systems.