Abstract: A device and method for containing spills and leaks from fuel handling equipment is provided in which differential sensing means detect the presence of hydrocarbons and nonhydrocarbons such as water. Signals and the responses generated according to them may depend upon the nature and quantity of the substance contained in the device. Signalling may be conducted remotely and excavation and reconstruction of service station grounds is minimized with these devices. In a preferred embodiment, the device is made of unitary construction with the differential sensing means formed as a portion of the surface of a containment vessel.