Comparison of various techniques for measuring natural ventillation in rooms

Various tracer gases were released into a room and the rate of decrease of their concentrations was used as a measure of the natural ventilation rate. Three different measurement instruments were used: an automated gas chromatograph, a gas sensor (for combustible gas), and a Geiger-Muller counter. The results of all three were in agreement. Complete mixing of all the tracers with the air inside the room required a period of at least 20min. The organohalogenated gases were found to affect the results of the gas sensor because of their strong adsorption on its detector surface. Despite stratification, of both tracer gas concentration and air temperature, there was no significant effect on measuement of natural ventilation rate.