Oxygen concentrator system comprising a portable oxygen generator unit adapted to generate a non-humidified oxygen-rich gas and a stationary base unit adapted to generate a humidified oxygen-rich gas, wherein the portable oxygen generator unit and the stationary base are adapted for operation in a coupled mode and an uncoupled mode. The portable oxygen generator unit includes a first flow coupling adapted to receive the humidified oxygen-rich gas when operating in the coupled mode, piping means adapted to combine the non-humidified oxygen-rich gas and the humidified oxygen-rich gas to form a humidified oxygen-rich gas product, and an oxygen-rich gas product delivery port. The stationary base unit is adapted to recharge a rechargeable power supply system in the portable oxygen generator unit when the units are coupled.