Applying the CO₂ concentration decay tracer gas method in long-term monitoring campaigns in occupied homes: identifying appropriate unoccupied periods and decay periods

Purpose Ventilation is driven by weather conditions, occupant actions and mechanical ventilation, so can be highly variable. This paper reports on the development of two analysis algorithms designed to facilitate investigation ventilation in occupied homes over time. Design/methodology/approach These application CO 2 concentration decay tracer gas technique. The first algorithm identifies periods. second periods decaying which assumed meet assumptions required for analysis. Findings were successfully applied four dwellings, giving 100 measurements during a six-month period three flats. specific implementation identification had important ramifications rates measured, highlighting importance interrogating way that appropriate are identified. Practical implications provide robust, reliable repeatable rate coded Python, these have been made available via GitHub. As well as supporting future experiments, could adapted different purposes, including use other gases or exploring exposure indoor air pollution. Originality/value Empirical investigations dwellings rarely aim investigate variability ventilation. methods used address this gap empirical evidence.