The air had thickened with shadows and he wanted to see my face.

I heard August move across the porch, felt the air thicken as she stood behind me on the other side of the screen.

At once the air between the three of them thickened.

As if the air had thickened, the light slumped off to the sides.

The air along the trail thickened with more than dusk.

So he thought of a force field, and saw the air thicken around the wild man.

The air around the humans thickened at the Weaver's approach.

Then the air thickened, by three o'clock it was dusk, and soon after four quite dark.

The air itself thickened, changing the quality of the light.

And the air thickened even more, making breathing totally impossible.