Elevator Hostway Pressurization System In case of fire, need to be supplied pressurized air into the fire fighting lobby(vestibule) to prevent the smoke infiltration for safe evacuation place and a bridgehead for fire fighter´s fire suppression by the conventional vertical duct and brick laying type. To keep differential pressure(over 40Pa) in the fire fighting lobby by the National Fire Safety Code, it is recommended to be used pressurized air supply through the elevator hoistway instead of conventional duct type for the purpose of space utilization and saving cost. VAVSP(Variable Air Volume System for Smoke Protection) The recommended differential pressure is over 40Pa due to the differential pressure inside the fire fighting lobby and the opening force of the door. It is needed to control fan RPM through inverter which can change variable voltage and frequency in the system by differential pressure measurement value between fire fighting lobby and corridor.