Air – we need it, part one

The atmosphere that encircles our planet protects and sustains all living things. The Stratosphere is home to the Ozone layer, some 12 to 25 miles above us, protecting us from solar radiation. The layer we spend our lives in, the lower portion of the Troposphere, provides that sustenance we all need - breathable air. What we breath includes various gases -- about 78 percent nitrogen, 21 percent ox...