Carbon nanotubes (CNTs), synthesized by thermal chemical vapor deposition, have been used to fabricate a prototype sensor. The sensor was investigated for its sensitivity towards different chamber pressure of ethanol vapor sat room temperature. Upon exposure to a with and without ethanol environment at room temperature, the electrical resistance of the sensor was found to increase even for ethanol vapor chamber pressure as low as 50mTorr and to return back respectively. It is proposed that hydrogen bonding of the functionalized groups on CNTs with adsorbed molecules is responsible for this response.