Abstract: A system for simulating a breathing lung is disclosed. The system comprises a lung model contained within an enclosure, wherein a main bronchus of the lung model is open to ambient air. In one embodiment, the system also comprises a vacuum pump connected to the enclosure, a first normally closed 2-way valve connected to the enclosure, a flow controller connected to both the vacuum pump and the enclosure, and a timer connected to the first normally closed 2-way valve. In alternative embodiments, the system comprises a first pump connected to the enclosure and a second pump connected to the enclosure, wherein the first and second pumps work independently of each other, and wherein the first pump is a vacuum pump, and the second pump is either a peristaltic pump or a piston pump.