Uncertainty analysis and optimum concentration decay term for air exchange rate measurements: Estimation methods for effective volume and infiltration rate

The widely used concentration decay method for measuring the single-zone air exchange rate has few limitations in its practical application, and several measurement standards employing this method have been published including ISO 12569, ASTM E741-95, and JIS A1406. These conventional methods, however, include several shortcomings that should be improved in terms of data analysis. Therefore, an equation for estimating the air exchange rate by the least-squares method from the number of points on the decay curve of the tracer gas and a method for determining the optimum decay term that minimizes the uncertainty are deduced. The method for calculating the standard deviation of uncertainty is also reconsidered and a new equation is deduced and verified. Furthermore, a method is introduced and verified for evaluating whether the premises of the measurement are sufficiently satisfied, such as the invariability of the air exchange rate and the uniformity of the tracer gas in the zone. In addition, a method for simultaneously estimating the effective mixing volume and the infiltration rate separately would be useful and is deduced. This estimation method’s accuracy, which depends on the waveform and frequency of gas emission, is investigated through numerical experiments.