In this work gas sensors based on PtSi Schottky diode using <100> n-type porous Si were designed, fabricated, and tested. These gas sensors detect polar gases (the gases with internal dipole moments) such as CO and non-polar gases (the gases without internal dipole moments) such as CO2. The operation of these Schottky diode sensors is carried out in breakdown region and shifts in their breakdown voltage in the presence of certain gases are mapped into the concentration of those gases in the environment. Fabrication of PtSi diode based gas sensors was reported earlier elsewhere. Our main objective in this work was to significantly reduce the breakdown voltage of these sensors hence making their use more economical. Such reduction was achieved through a series of systematic changes and optimization in the pore's geometries by careful study, analysis, and changes in the experimental conditions such as temperature, acid concentration, chemistry of the etching solution, and time.