Air quality, contaminants and odors should all be considered in designing a ventilation system for a negative isolation room. The system should be capable of preventing bacteria and pathogen contaminants from entering the room. The need for air supply based on ACH must be met to keep the pressure space positive. System filters play an important role in creating clean air quality. This study used air flow modeling with FloVent 8.2. The result compared the existing design with the design proposed to conform with isolation room standards with negative pressure. The existing design shown that outdoor intake was too high, which resulted in high air velocity above the bed. The amount of particles were also incompatible to standards. The new design shown that the air velocity above the patient's bed was 1,4 m/s, the temperature was 22 °C and the pressure was - 1,9 Pa. These parameters accorded with the standards. The air flow pattern towards the HEPA filter was laminar.