Design, development and test of a low cost, fast-response, multi-gas tracer gas measurement apparatus

Tracer gas measurements are a family of well know and widely applied experimental techniques adopted to test and verify the performance of ventilation and air conditioning systems. They are aimed at measuring either the ventilation air flow rates and or the performance of the air distribution. They make use of nontoxic, non-flammable, odourless and easy to detect gasses that are injected in the air and whose concentration is then monitored over a period of time. For this sake quite sophisticated, costly and delicate measuring apparatuses are typically used. The main disadvantages of the existing apparatuses are represented by their cost, size and the impossibility of leaving the system in the field for medium/long term monitoring campaigns. Besides, the time response is usually rather long and this hinder their use in all those cases where the ventilation air flow rates are high or when many measuring points need to be monitored simultaneously. For these reasons a new measuring system (TEBE-SENSE) was designed and built. It adopts a number of small, wireless measuring devices that can communicate with a central unit and can measure, store and elaborate the time histories of the tracer gas. The measurement apparatus is developed, so far, to work with three different tracer gases simultaneously (e.g. CO2, SF6, Propane), allowing also the analysis of inter-zonal air exchanges. The response time is in the order of a fraction of a second, a feature that allows to properly follow fast transient ventilation phenomena and to analyse strongly ventilated environments. In this paper the main features of this new system will be presented. A validation was done by comparing the results obtained with the newly proposed system with those provided by a traditional photoacoustic measurement apparatus.