The need to apply high operation temperature when working with metal oxide gas sensors is a Well-known drawback of these kinds of gas sensors in spite of their wide applications even commercially. In this approach, a new strategy was introduced for gas sensing with metal oxides in ambient temperature. The principal is based on the addition of a desiccant material in the metal oxide based nanocomposite. For this aim, nano-sized alpha-Fe2O3, a graphite and calcium sulfate was combined and the nanocomposite obtained was used as an efficient gas sensor. Calcium sulfate was used either as desiccant or binder to tighten together the nonocomposite components. Sensing nanocomposite was tested for sensing of dimethyl methylphosphonate (DMMP) vapor, as a nerve agent stimulant. The results obtained showed excellent sensitivity and selectivity for DMMP. It was demonstrated that the presence of CaSO4 in the nanocomposite is crucially important for observing the sensing characteristic of nano-sized alpha-Fe2O3 in room temperature. It was also shown that the modification of iron oxide with sulfate functionalities improved the DMMP detection capability of the related nanocomposite. Based on the observed result a mechanism was proposed for sensing performance of the sensor. The developed sensor showed very low detection limit of 1 ppb for DMM. (C) 2015 Elsevier B.V. All rights reserved.