COVID-19 was declared a pandemic by the WHO in March 2020 following its outbreak in December 2019. South Korea faced a shortage of hospital beds due to the increasing number of ill patients. In response, the Korean government decided to quickly convert general hospital room into Airborne Infection Isolation (AII) room so that infected patients could be treated in an isolated environment. In this study, the conversion performance and contaminant control performance of the Convertible Air Handling Unit for AIIR (CAHU), which was developed to convert general hospital rooms into AIIRs quickly, were verified through experiments. The particle experiment was conducted in a full-scale chamber with an CAHU system installed. Particles were generated near the patient’s head and tested for reintroduction through the air handling unit, leakage to adjacent rooms, and concentration reduction. The experiment was divided into three cases. The contaminant control performance was analyzed by conversion from the normal mode(recirculation) to the AIIR mode (100% outdoor air, full exhaust), operating at pressure differences of −3, −5, and −7 Pa. The experimental results confirmed particle leakage into the adjacent room when in recirculation mode. When conversion to AIIR mode, the concentration in the adjacent room quickly reduced, and the pressure difference was kept stable. No particle outflow was observed during the AIIR mode operation. The higher the pressure difference, the shorter the concentration recovery time after the end of the particle generation was observed. The results indicate that CAHU can be utilized during pandemics to quickly convert from a normal hospital room to an AIIR and vice versa.