This paper presents the performance of CMOS-SOI TMOS thermal sensor processed in a well-established 1μm technology, operating in air. The TMOS is a micro-machined CMOS transistor, operating at subthreshold. The thermally isolated floating MOS transistor senses temperature changes induced by either a physical or a chemical phenomenon. The change in temperature modifies the threshold voltage and accordingly the I-V characteristics of the micro-machined transistor. Operation in air, without vacuum packaging, enables low-cost products for a wide range of low-cost commercial mobile applications such as IoT, wearables, smart homes and smartphones.