An apparatus and method for characterizing gas flow through features fabricated in a hollow part. A pressure regulated cooled gas is applied to an interior of the part to the features fabricated in the part. At the same time, a pressure regulated heated gas is applied to an exterior part skin; and the heated gas has a controlled temperature differential from the pressure regulated cooled gas applied to the part interior. An infrared signature of escaping gas and the surrounding part skin is analyzed by a classification method to identify acceptable and unacceptable fabricated features.