This paper deals with how to visibly render the thermal climate in the design and presentationtools used by different participants in the building process. The focus is on those ventilation/coolingsystems where cool air is supplied directly into the occupied zone and therefore have a potential ofgenerating a volume close to the device with poor comfort. This volume could be described as a spreading bubble. In the paper a practical procedure for rendering the spreading bubble is presented. This is achieved in a number of steps. The first step is to collect data of the velocity and temperature field near the device. A further step is to manipulate the collected data and to generate the spreading volume. The final product consist of two modules, the device itself and the spreading bubble at different operating conditions.