Reactive surfaces are increasingly being used in products ranging from batteries and fuel cells to bio-coated films used for bio and chemical destruction or detection. One of the common features to these coatings is a reactive element or compound. In processing these layers it is often difficult to assess the activity of the reactive layer unless destructive tests are used on selected samples, thus preventing its use in its intended application. To address this dilemma, a hand-held non-destructive probe has been developed that can be used to quantify the propensity of a reactive film to chemically react as intended before it is incorporated into a higher value product. This sensor is amenable to operation in high volume manufacturing processes where reactive films or layers are continuously fabricated. Development of the probe will be presented along with its demonstrated utility in assessing the reactivity of a variety of reactive surfaces including platinized membrane films, catalytic mesh screens, catalyst powders, biofilms, and plating baths.