A multitracer system for multizone ventilation measurement.

Mass transfer due to pressure-driven air flow is one of the most important processes for determining both environmental quality and energy requirements in buildings. Heat, moisture, and contaminants are all transported by air movement between indoors and outdoors as well as between different zones within a building. Measurement of these air flows are critical to understanding the performance of buildings. Virtually all measurements of ventilation are made using the dilution of a tracer gas. The vast ma,jority of such measurements have been made in a single zone, using a single tracer gas. For the past several years LBL has been developing the MultiTracer Measurement System (MTMS) to provide full multizone air flow inform~tion in an accurate, real-time manner. MTMS is based on a quadrupole mass spectrometer to provide highspeed concentration analysis of multiple tracer gasses in the (low) ppm level which are injected into multiple zones using mass flow controllers. The measurement and injection system is controlled by a PC and can measure all concentrations in all zones (and adjust the injected tracer flows) within two minutes and can operate unattended for weeks. The resulting injection-rate and concentration data can be analyzed to infer the bulk air movement between zones. The system also measures related quantities such as weather and zonal temperature to assist in the data interpretation. Using MTMS field measurements have been made for the past two years.