ADOPTED_FROM:EN ISO 12569:2000 This standard describes the use of tracer gas dilution for determining a single zone's air change 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 analyzer. Air change rate is directly calculated from the rate of change of tracer gas concentration by the tracer gas method. Airflow rate is calculated directly from the tracer gas flow rate by the constant injection or constant concentration method.