This International Standard establishes an engineering standard by which to obtain the ventilation rate/specific airflow rate, using a tracer gas in a building space, which is considered to be of a single zone. The measurement method is valid in spaces where the combined conditions concerning the uniformity of tracer gas concentration, measurement of the exhaust gas concentration, effective mixed zone and/or fluctuation of ventilation are satisfied. This International Standard provides three measurement methods using a tracer gas: (1) concentration decay method, (2) continuous dose method, and (3) constant concentration method. NOTE Specific measurement conditions are given in Table 1.