Abstract: A leak detection and prevention system adapted to continuously monitor the spaces of a double wall hydrocarbon fuel handling system comprising storage tanks, product lines, vapor recovery lines, tank vent lines, etc. The system establishes and monitors a resident gas-pressure within the interstitial space to monitor the integrity of the primary and secondary containment. Change in resident gas-pressure in excess of a calibrated vacuum flow rate or the presence of liquid in any monitored space initiates an alarm. Once an alarm is signaled, the product delivery system is shut down and an audio-visual alarm is activated in close proximity to operating personnel. An onsite service call by qualified personnel is required to return the product handling system back into service. A qualified service technician connects to a communication port on the system control module to evaluate the cause of the failure. The system utilizes vacuum pressure to monitor for containment breaches.