Multi-chamber air renewal survey using constant concentration tracer-gas technique. Mesures du taux de renouvellement d'air a l'aide d'un dispositif compact a concentration constante.

An accurate determination of air renewal rate and connective exchanges between units was needed for study of the solar units of the experimental building LESO, in both an occupied and empty state. The CESAR compact equipment for tracer gas (nitrous oxide) measurement was developed. This unit uses a microcomputer to perform a simultaneous and periodical gas analysis in 10 locations. Three tracer gas methods can be used: decay, constant concentration, and continuous flow. The device and regulating program work well with low rates of concentration (100ppm of nitrous oxide). The measurements by decay and constant concentration give similar results and with the simultaneous survey of the 10 rooms, a comparison between air movement and infiltration is possible. Occupancy effects can also be evaluated.