At around 8.20 a.m., after loading 1.5t of propane into a tank, a cloud of gas formed around the venting device and pressure relief system of a truck at a fuel business. The gas leak was small and detectors nearby were not triggered. The pump operator activated the emergency shutdown, causing ongoing transfers to shut down, valves to close, and automatic sprinklers to start up. Employees gathered at the assembly point. A mechanic closed the pressure relief system’s valve. The leak stopped. At around 8.35 a.m., the truck was transferred to the workshop to check the tank’s systems. The site’s systems were reset, and operations resumed.

The following anomalies, which caused the leak, were detected on the truck:

• loose truck pump pressure relief system connection;
• system vent valve in open position;
• manual feed valve not closed;
• “gas/liquid” selector at rear of truck in neutral position.

Causes of these anomalies: the truck had been assigned to delivery duty urgently even though its maintenance (started the previous week) had not been completed. There were no visual indicators on the vehicle enabling its identification.

Following the event, the operator put in place the following corrective actions:

• teaching pump operators about this type of event;
• modifying pump operator loading instructions, adding visual checking of selector position;
• the liquid gas transport committee (France) drawing up safety information for hauliers requiring tracking of vehicles undergoing maintenance;
• the driver was again required to be monitored by an instructor.