But the air keeps on rising until it reaches around 15 km.

So, outside where chilly air kept them walking fast, she talked.

We build off the ground so air circulates under the floor and keeps that cool.

Still, air can collect in the radiators and keep the hot water out.

The air keeps replacing itself, more or less, by volcanic action.

The air was cold, but the sun shone and kept the chill from being bitter.

This is why the air does not keep its low pressure after leaving the wing.

The air kept catching in her throat, making each breath she took like a small spasm.

What struck me as the most curious thing about this wonderful river was: how did the air keep fresh?

"The air in your lungs will keep you afloat," he promised.