In this work, we report the effect of post-deposition film treatment on the NO2 sensing properties of CuPc thin films for room temperature operation. The gas-sensitive response of the electrical conductivity to doping with NO2, doping with oxygen (in air) and cooling to 77 K in liquid nitrogen are reported. The pretreatment with NO2 is shown to improve the gas sensing properties by providing both an increase in the magnitude of the conductivity change for a given NO2 concentration and a significant improvement in the recovery time. Data is analyzed using an Elovich model, which suggests that the cooled devices have the best fit to this model; the data for the NO2 doped devices suggest a Langmuir behaviour. For all devices, a simple time derivative of the change in current provides a measure of concentration for real time gas sensing applications.