A new tracer-gas testing technique: Theory and numerical simulations

Abstract

A new technique is presented for measuring air exchange rates and contaminant transfer dynamics in buildings. The method uses pseudo-random binary sequences (PRBS) to control tracer-gas injection. Cross-correlation of the injection sequence with the tracer concentrations measured in multiple rooms is used to deduce system responses. Air flow rates in multiple-room buildings can be measured simultaneously using a single tracer. Both dynamic air-change rates and static flow rates can be determined, and bad mixing can be diagnosed and quantified. Traditional techniques for tracer gas testing are reviewed followed by a derivation of the new method. Numerical simulation trials of the technique are described, the first for a simple one-room configuration, the second for the same situation with experimental noise added, and the third for a three-room building. The results obtained by cross-correlation agree with the known impulse responses and air change rates providing a first proof of concept for the method. A subsequent paper will describe validation of the method in a multi-room test chamber.