Describes tests conducted in a full-scale office room with internal heat loads and furnishings to analyse and estimate the accuracy and repeatability of the pulse and step-down tracer gas methods for measuring mean ages of air. Finds that the error band due to the combined effect of the limited accuracy and repeatability was wider for the pulse method than for the step-down method. Provides an example to illustrate how these results can be used to interpret the measurement of mean ages of air in evaluating the performance of ventilation systems.

KEYWORDS: year 1995, Measuring, ventilation, tracers, offices, accuracy, measuring, performance