A British geologist has volunteered to spend 48 hours in an airtight chamber relying on the oxygen produced by plants to survive.Iain Stewart, a professor at the University of Plymouth, will share the 12 metre-square (129 square feet) chamber with dozens of specially chosen plants on September 16 and 17, as well as a hammock, a laptop and an exercise bike. Specialist lights both inside and outside the clear perspex chamber will operate continuously to provide the energy the plants need for photosynthesis. The levels of oxygen and carbon dioxide produced will be closely monitored and Stewart will be attached to medical sensors which monitor his vital signs. \"This experiment has never been done before with a human -- it seems a fascinating challenge to see if plants really could keep a person alive,\" Stewart said. It echoes an experiment first tried by scientist Joseph Priestly in the 1770s, when he showed how a mouse could survive in an airtight chamber full of plants, but not in a box without them.The stunt will take place at the Eden Project, an environmental visitor attraction in Cornwall, southwest England, and will be filmed for a BBC documentary series. \"We often overlook the role of plants in sustaining life on Earth. We hope this will bring home to viewers in a compelling and revelatory way just how crucial they are to our existence,\" said TV producer Andrew Thompson.