1.   As a general rule, however, high-altitude rescues involving helicopters are considered risky because of the thinner air and unpredictable winds.

2.   As the plane climbed into thinner air, fumes from the empty space in the tank would have been venting, and might have ignited outside the plane somehow.

3.   Higher areas have thinner air, and lower atmospheric pressure.

4.   In addition, he said he will rotate more players in to lessen the affects of the thinner air.

5.   It is possible, Levine speculated, that such athletes must be exposed to even thinner air to respond.

6.   Some members of its party clearly are having a hard time adapting to the thinner air.

7.   We then proceeded on a more or less horizontal walk, but we were now breathing thinner air than the previous day on the valley floor.

8.   Peru will next get Bolivia in the even thinner air of La Paz on Sunday, and then get Venezuela to finish the group on Wednesday.

9.   Flying at high-elevation airports can be difficult because the thinner air detracts from aircraft performance in several ways.

10.   Some visitors may need a day or two to adjust to breathing the thinner air.