In recent years, carbon materials are widely investigated because of they are enormously sensitive to H-2 at room temperature conditions. In the present work, the inexpensive candle carbon soot (CCS) is used to detect 0.5% concentration of H-2 gas at room temperature. A simple flame of candle is used to synthesize the layers of carbon soot at room temperature conditions. It is observed that, the acid treatment of CCS drastically improved their structural and sensing properties as compared to as-synthesized CCS. The effect of acid functionalization on the CCS structure were investigated by X-ray diffraction (XRD) and Raman spectroscopy. To the best of our knowledge, detection of low concentrations of H-2 gas is reported here for the first time using economical CCS at room temperature. (C) 2020 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.