Abstract: High impedance fault detection uses, in addition to sensors that measure purely electrical (i.e., current and voltage), molecule sensors are provided in an electrical grid. These molecule sensors are sensitive to the surrounding environment and may detect one or more of a variety of molecules, such as ozone (O3), combustion gases (carbon monoxide, carbon dioxide and oxygen levels), and odor molecules (ammonia, sulfur dioxide, burned hair/feather, burned proteins, and the like), depending on the type of environmental phenomena that may be expected in a particular location of the sensor(s). These sensors, in combination with conventional electrical sensors, provide a more complete set of data for evaluation and localization of a potential high impedance electrical fault. The use of such sensors is especially useful in confined areas like underground parking lots, substations, and the like.