Transcription: To prepare for an extravehicular activity, astronauts use a time-efficient procedure to acclimate to the change in air from that of the oxygen-nitrogen mixture in the crew cabin to the pure oxygen which pressurizes the extravehicular mobility unit or EMU spacesuit. Proceeding directly from breathing the cabin air to pure oxygen in the suit could cause the bends, a painful and potentially crippling condition that lets nitrogen form bubbles in the bloodstream.
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