Abstarct: The last few years has witnessed a great and growing interest in porous silicon gas sensors. Low power consumption and room temperature operation of these sensors are the two main features that make porous silicon gas sensors superior to mextal-oxide gas sensors. The objective of this experimental research was to build and operate a number of porous silicon gas sensors and study their current-voltage characteristics at room temperature. The samples were made by electrochemical procedure using p-type crystalline Si (100) wafer. The effects of various parameters on CO2, methanol, ethanol and acetone gas sensing were studied. These parameters include: the electrolyte HF acid concentration, the magnitude of the applied current density and the preparation times. In the course of study, we used Scanning Electron Microscopy (SEM) and Photoluminescence (PL) apparatus to find out the surface morphology and the relative porosity of the grown samples. Our experimental results showed that the magnitude of porosity is the principal factor that affects gas sensing and the optimum condition could be achieved by varying different growth parameters.