An appraisal of the sulphur hexafluoride decay technique for measuring air infiltration rates in buildings.

Compares the air change rates measured with SF6 and CO2 using the tracer gas decay technique and the fan extraction method over a wide variety of test chamber sizes and mixing systems. Shows that the conventional air handling orportable floor fans can provide adequate mixing for SF6 tracer gas decay measurements of infiltration. Warns that the mixing operation may become the dominant driving force of infiltration during calm climatic conditions. Finds that +-0.08 ach/h is a reasonable measure of experimental error at the 95%confidence level using SF6 as the tracer gas. There is a small difference between the behaviour of CO2 and SF6 that leads to relatively high SF6 results above 0.5 ach/h and relatively low results below.