An air drying system for OBOGS is provided. The system comprises a bypass valve having an opened state and a closed state. The bypass valve is in fluid communication with an air inlet providing pressurized air. A dryer unit is configured to produce dried air when the bypass valve is in the closed state. An OBOGS unit produces oxygen enriched air while a purge valve has an opened state and a closed state. When the bypass valve is its closed state, the purge valve is in its opened state thereby directing a portion of the dried air to the oxygen generating system unit and a portion of the dried air to the dryer unit. When the bypass valve is its open state the pressurized air passes directly to the OBOGS unit.