Prof Andrea Sella demonstrates the convenience and power of this bulk chemical, whilst Laurence Knight heads to BOC's air separation unit in Fawley to see how it is mass produced.

Meanwhile Justin climbs a mountain, scuba dives and pedals like mad on an exercise bike inside a low oxygen chamber. But it's all in the name of science, as husband-and-wife medics-cum-mountaineers Denny Levett and Mike Grocott explain.