This work reports on the reliability testing of micromachined hotplates designed for calorimetric gas sensors. The devices consist of a platinum resistive heater on a silicon nitride substrate under which polysilicon has been etched. The devices have proprietary catalysts deposited onto the surface prior to reliability testing. Environmental, mechanical and electrical tests were performed on the devices. IR thermography work is described to demonstrate device processing issues as observed during some reliability tests. In general devices showed good mechanical stability, but the catalytic material deposited on the sensors showed some problems.