Supercritical air at cryogenic temperature is an attractive source of breathing air because of its very high density and low pressure. However, heat leak into the cryogenic tank causes the stored air to expand and vent, thus limiting the storage life of a charged system. We propose to develop a storage system for supercritical air packs that provides cryogenic cooling that will enable long-term storage of charged, supercritical air packs with zero venting. In Phase I we proved feasibility through design trade-off and optimization analyses that led to a conceptual design and operational description of a supercritical air storage system. The innovative, mechanical cryocooling system provides flexible coupling and quick disconnection, as well as high reliability and efficient, low-power operation. The system can be used to charge the tanks with supercritical air without the use of expendable cryogens. In Phase II we will build and demonstrate a prototype storage system for supercritical air self-contained breathing apparatus (SCBAs). Critical components will be designed and tested individually, then integrated to produce a complete cooling system. We will couple the Phase II prototype with a supercritical air pack and demonstrate long-term storage with zero venting.