Exhaust-only ventilation~ uses a fan to move indoor air out of your room
Supply-only ventilation ~ use of fan to bring in filtered fresh air inside room
Balanced ventilation~ Balanced ventilation systems, if properly designed and installed, neither pressurize nor depressurize your room. Rather, they introduce and exhaust approximately equal quantities of fresh outside air and polluted inside air. A balanced ventilation system usually has two fans and two duct systems.