11.   As they looked through military binoculars the sharp crack of a sniper rifle tore through the thin mountain air.

12.   Back then, mountain air was considered a cure for tuberculosis and other maladies.

13.   After long days of digging ditches in the thin mountain air, firefighters often camp within sight of the enemy.

14.   Briggs said that the heavy, cold mountain air was not good for his asthma.

15.   But the Rockies have been built to take advantage of the thin mountain air.

16.   But this year, far fewer are fleeing the baked plains for the cool mountain air.

17.   Details of the ensuing argument that spiced the chilly, still mountain air has not been included in this family newspaper -- partly because it transpired entirely in German.

18.   Every morning, large snowcats carry guests up through the crisp mountain air to begin a day of white revelry.

19.   For years, many endurance athletes have believed that exercising in thin mountain air is the best way to improve performance at sea level.

20.   Hiking in that mountain air may not be that good for you.