MODEL RELEASED. Heart valve frozen storage. Technician in gloves, mask and protective clothing inserts a container of donated aortic valves into liquid nitrogen. The vapour rising from the large cylinder is composed of water droplets condensed from the air by the extremely low temperature (below -198 degrees Celsius) of the nitrogen. The valves are quickly frozen and can be preserved until needed. The aortic valve lies between the left ventricle of the heart (main pumping chamber) and the aorta, the body's largest artery. It can be removed from donated hearts and transplanted into patients whose valves are malfunctioning due to disease.