Attempts were made to understand the analyte sensing mechanisms exhibited by CrNbO4 and Ag6Mo10O33 towards hydrogen and ammonia, respectively. Participation of lattice oxygen in sensing of hydrogen by CrNbO4 was elucidated. Direct reaction of Ag6Mo10O33 with ammonia was established in the sensing process. These findings were compared with the conventional sensing of hydrogen by tin oxide, which was mediated by chemisorbed oxygen species.