Tracer-gas techniques have become widely used to measure the ventilation rates in buildings. A tracer gas is an idealized substance used to tag volumes of air so as to be able to infer their bulk movement; the properties of a perfect tracer are discussed. The basic principle involved is that of canservation of mass (of both air and tracer gas) as expressed in the continuity equation; by monitoring the injection and concentration of the tracer, one can infer the exchange of air. This report will summarize the techniques in use.
This paper describes tracer gas methods and equipment developed to measure infiltration and inter-zone air flow rates in New Zealand houses. Air flows in houses have been studied in detail, in order to understand the role of ventilation in controlling indoor moisture, and the role of air flows through the construction cavities in transferring mloisture to parts of the structure most sensitive to moisture. The main technical content of this paper, however, concerns an automated tracer gas detection and delivery system based around a gas chromatograph and an electron capture detector.