Research and development of solid state gas sensor devices began in the 1950s with several uncoordinated independent efforts. The number and pace of these investigations later accelerated in response to increasing pressure placed on the environment and public health by industrial activities. Since 1970, several thousand articles have been written on the subject, and laboratories around the globe have introduced novel methodologies and devices to address needs associated with particular technological developments. Despite the rapid development of this important new technology, very little...