Airborne molecular species (AMS) are a desirable target for detection in ultra-low concentrations in many fields of industry. The detection of explosives in gas phase can reduce security threats and lower costs all around the world. In medicine AMS emitted by respiration and through the skin can help in early detection of diseases and conditions. In our research the detection was done by exploiting the electric characteristics of Si nanowire field-effect transistors sensors (Si NWFET). The use of SiNW FET are showing promising capabilities in the recognition of the contaminating species, even at low concentrations as low as ~10ppt (parts-per-trillion) in their gaseous phase. SiNW FETs provide advantages when compared to other sensing methods such as: low power consumption, gate voltage controllability, simple multiple device signals analysis, and their small dimensions [2]. We will present a novel use of SiNW FETs to detect AMSs, with detection time of a few seconds. By heating permeation tubes in an oven, with a constant flow of N2 carrying gas, we were able to control the concentration of the AMSs. In order to detect the AMSs we have modified the SiNWs surface with different silane-derivative molecular layers, and tested the change of electrical current through the NWs devices in response to their interaction with the AMSs molecular species. The AMS molecules, physisorbed to the modified SiNWs surface, induced a change in the surface potential of the NW-based sensing devices, which resulted in change of current through the NWs. In this work we have successfully tested the presence of Acetone and NMP molecules, while using different modifications.