Compact diagnostic testing device

A compact hand-held diagnostic device includes at least one chemical sensing element mounted to an external surface of a substrate, the chemical sensing element being capable of detecting at least one chemical component indicative of a condition of a target and producing an electrical change when said at least one chemical component is detected. The device includes a processor for processing electrical changes produced by the chemical sensing elements into a resulting signal and at least one indicator connected to the processor for indicating the presence of a detected chemical component and in which the chemical sensing element is directly exposed to the target environment without requiring any portion of the environment to first be drawn into the device. The compact device can be used in both medical and industrial applications.