Determination of air change rates - use of tracers.

One of the main aspects determining the thermal behaviour of buildings concerns the distribution and circulation of air. Experimentation was undertaken in the context of the investigation of a method of measurement of the natural ventilation of large rooms. The first objective was to endeavour to characterise the atmospheric conditions around the building, namely, conditions related to wind factors, but also those concerned with the location of the building in relation to neighbouring obstacles (other buildings, relief of the ground, etc). The relationship between the concentration of a tracer and the ventilation system was then studied, using various hypotheses. The aim of the experimentation was to define a method, based on selection of tracer, homogenisation of the atmosphere and representativeness of measurements. The research resulted in the determination of a practical method.