This thesis deals with the fabrication of MEMS air quality sensors for automotive applications. The goal of this project is to design, fabricate and test an integrated sensor that measures three important air quality components inside the automotive cabin, which are temperature, relative humidity and carbon monoxide (CO) concentration. The sensors are fabricated on silicon substrate covered with thermal oxide and LPCVD nitride. Various deposition and etching techniques were utilized to fabricate these sensors including E-beam evaporation, thermal oxide growth, PECVD, LPCVD, RIE, KOH and HF etching. The temperature and humidity sensor use nickel as the sensitive material while the CO sensor was designed to use SnO₂ although it was not fabricated to completion. A chamber was created where the temperature and humidity are controlled and the sensors were tested. Curves of sensor resistance vs. temperature and sensor resistance vs. humidity were created and the two sensor’s sensitivity was calculated.