This paper reviews solid-state gas sensing techniques that could be developed to supersede the NDIR bench and the electrochemical cell that are presently used in the majority of aftermarket emission analysers. Techniques considered include acoustic wave devices, chemfets, chemi-resistors and optical devices. Technical performance, e.g. sensitivity, selectivity, stability and speed of response, are assessed and compared. Manufacturability, cost, interfacing and processing requirements are also examined. The capability for inclusion in a hand-held analyser unit is the key consideration. Techniques that meet the review criteria are identified and recommendations are made as to requirements for further research and development.