Tracer gas technology for airflow measurements in HVAC systems

This paper describes the use of tracer gas techniques for airflow measurement in ducts. The author had carried out extensive work in both the laboratory and the field to test the accuracy and viability of these techniques. Preliminary measurements were carried out in the laboratory to examine the accuracy of these techniques. The mixing of tracer gas (e.g. sulphur hexafluoride, SF6) in ducts of various shapes and sizes was examined using different types of tracer injectors. Measurements of airflow estimated using tracer gas techniques (e.g. constant-injection, pulse-injection) were compared with measurements made using traditional instrumentation such as pitot tubes. Field testing on a large-scale heating, ventilation and air-conditioning system was carried out and tracer gas techniques were used to determine airflow rates in air handling units serving a library building.