The future of passive techniques in air change rate measurement

Ventilation is critical in interpreting indoor air quality (IAQ), but only few IAQ assessments report ventilation rates; even when they do, the measurement method is often not fully de-scribed. Most ventilation assessments use a tracer gas test (TGT) approach to measure total air change rate, which consists in marking the indoor air with an easily identifiable gas (tracer) and then inferring the air exchange rate by monitoring the tracer’s injection rate and concen-tration (Persily, 2016). For this monitoring, two sampling options can be used: active sam-plers, costly and complex, or passive samplers (which work by absorption/adsorption without electricity use), overall more advantageous: cheaper, smaller, lighter, simpler and silent. Af-fordable passive samplers are commercialized by a range of companies and are already widely used in IAQ studies to analyse the presence of several gaseous pollutants (Stranger et al., 2008). However, currently employed TGTs in IAQ assessments are either active or not con-ceived to be executed together with common IAQ analysis, providing ventilation rates in a different time-scale than the pollutant concentrations. Thus, this paper proposes a new ap-proach for the TGT method, using as tracer a substance that can be co-captured and co-analysed using commercial passive samplers commonly used in IAQ studies