In this paper we report on the characterisation of a smart ASIC chip comprising a pair of room temperature resistive vapour sensors in a ratiometric configuration. This novel design enables the near elimination of several undesirable baseline effects and provides an automatic offset of the output signal. The novel ASIC chip has been designed and fabricated through a standard 0.7 μm CMOS process. The ASIC response has been modelled prior to fabrication as reported elsewhere. There are two main stages in the circuit: one for the processing and conditioning of the sensor signals and the other for temperature control. Two sets of sensor electrodes are positioned in two opposite corners of the chip and are connected in a non-inverting operational amplifier configuration. Carbon black/polymer composite materials have been deposited across the electrodes to create the sensing chemoresistors and illustrate the functionality of the chip. Sample devices were created by depositing either the same nanomaterial on both electrodes and having one active and one passive sensor, or by depositing two different materials, thus creating two active sensors. Following deposition, the responses of the ASIC devices to toluene and ethanol vapours in air have been characterised in an automated mass flow system and presented here.