thin film 105 in the form of a strip on an electrically insulating substrate 110 a pair of electrically conductive electrodes 115 120 is electrically coupled to the ito thin film 105 with one electrode at each opposite end of the thin film the electrodes 115 120 may be electrically coupled to monitoring equipment configured to measure one or more electrical characteristics of the thin film 105 such as resistance across the film 105 over time the resistance of the ito thin film 105 will change over time in an identifiable manner shortly after the thin film is exposed to a particular cwa thus monitoring resistance over time enables determination of the presence of a cwa as well as identification of the cwa advantageously the sensor 100 may be used to identify any cwa for which a characteristic electrical response has been determined fig2 provides a perspective view of an exemplary sensor slide 200 with a sensor array according to principles of the invention a plurality of ito thin film sensor strips 210 are formed on an insulator substrate 215 the sensor strips 210 share a common central electrode 220 with several discrete interface pads 205 225 230 and 235 the common central electrode 220 is electrically coupled to each sensor strip 210 at approximately the midpoint of the strip 210 an end electrode 240 245 is operably coupled to each end of each ito thin film strip 210 thus each strip 210 provides two sensors i e.