COMPARISON OF PFT METHOD WITH SF6 CONSTANT-INJECTION, CO2 CONSTANT-CONCENTRATION AND THEORETICAL CALCULATION METHOD FOR VENTILATION MEASUREMENT UNDER CYCLIC REVERSAL

Abstract

Simpler and easier measurement method is required for ventilation rate. Improved PFT (Perfluorocarbon Tracergas) method by our group, which is a passive constant emission and passive sampling system, is applied in this paper. In order to verify the precision of PFT method, field measurements were conducted using three tracer gas techniques (PFT passive constant-emission, SF6 constant-injection and CO2 constant-concentration method) in a multi-family residential building with pressure control chambers. Differential pressures between indoor and outdoor were measured simultaneously and ventilation rates were calculated. Four measurement methods were applied simultaneously under four ventilation conditions. PFT method may include its unique errors referred from passive technique and might overestimate AERs (Air Exchange Rates) in cyclic reversal conditions of airflow. Under all other conditions except PFT method of condition 3, the results obtained from four methods agreed well with each other. In addition, as a result of the numerical calculation, the PFT method was suggested that it might have possibility to overevaluate a ventilation rate when the reversing cycle was relatively long over the stationary state arrival time. Under disturbance conditions except a long term cyclic reversal of airflow, however, the availability of PFT method for ventilation rate was verified.