This standard describes the use of tracer gas dilution for determining the air change in a single zone as induced by weather conditions or mechanical ventilation. The procedures for tracer gas dilution include concentration decay, constant injection, and constant concentration. Tracer gas concentration is determined by a gas analyser. Air change rate is directly calculated from the rate of change of tracer gas concentration by the tracer gas decay method. Air flow rate is calculated directly from the tracer gas flow rate by the constant injection or constant concentration method.