Detection of toxic gases like carbonmonoxide, nitrogen oxide,methane and sulphur dioxide is extremely important, since they have destructive effects on human health. SO2 is reported to be extremely toxic to humans especially to the respiratory system, eyes and skin. For this purpose there is immediate need for roomtemperature, low-cost, sensitive and reliable gas sensors. We can detect some of these gases with special type of substrate and sensing material. Sensor synthesis using nanoparticle is very important part of this project. Nanomaterial in thin filmformhas capability to achieve desired task due to its properties like high surface to volume ratio and small size. Spray pyrolysis technique was used for creative of SnO2, V2O5 and V2O5: SnO2 thin films. In this article preparing of different gas sensors with different substrate (SnO2, V2O5and V2O5: SnO2composite bilayer) are tested. Room temperature gas sensing for pure SnO2, pure V2O5 and composite system, it is observed that response and recovery of individual sample is very slow where as Composite system shows very fast response and recovery of the order of 30 seconds which could be attributed to fast operated devices and it may also used as real time sensing systems. Sensitivity of Pure samples is better than composite.