1. A feature inspection system for inspecting a feature extending from a cavity: within a structure to an outer surface of the structure, the feature inspection system comprising: a first gas of a first density adapted to flow over the outer surface around the feature; a second gas of a second density different from the first density and adapted to flow into the cavity and through the feature; an infrared camera adapted to provide a thermal image of an area of the outer surface around the feature, the thermal image comprising temperature feedback signals representing a plurality of temperatures; and a control in electrical communications with the infrared camera and causing the first gas and the second gas to simultaneously flow over the outer surface and through the feature, respectively, and the control processing the temperature feedback signals to identify a qualitative characteristic of the feature.