What is the correct priority order for shutting down gas valves?

The correct priority order for shutting down gas valves is to begin with the appliance valve, followed by the interior gas riser valve, the curb valve, and finally, the main valve. This sequence is essential for ensuring safety and preventing gas from accumulating in various locations.

Starting with the appliance valve is crucial because it addresses the immediate source of gas that could potentially lead to a fire or explosion if not managed promptly. By shutting down the appliance first, you immediately cut off the flow of gas to any operating appliances that may pose a danger.

Following that, shutting off the interior gas riser valve prevents gas from moving up the system, which could lead to potential hazards within the building. This step is important to ensure that, even if there are leaks present, gas does not flow into other areas of the structure.

The curb valve is next in line for shutdown, as it acts as a control point for gas entering the building. Finally, the main valve is shut down to completely isolate the building from the external gas supply, ensuring that no further gas influx can occur.

Understanding this order is vital for effective emergency response and safety management when dealing with gas-related incidents. Improper sequencing could lead to critical safety oversights.