Twenty years ago, each one of these deep caves was nothing but unbreathable air and dark, empty rock.

A moonless world the size and mass of Earth should have unbreathable air, impossibly dense, worse than Venus.

The unbreathable air exhausted from the cab and was replaced by proper gas.

If only you could do something about this unbreathable air-" "Wait awhile.

The absence of such an indignation is the most significant contribution to our country's morally unbreathable air.

A tube ruptured within the shuttle's ceiling, spraying vaporized coolant into the cabin, further polluting the increasingly unbreathable air.

A yellow haze of brimstone coloured the unbreathable air and the room shook and shivered beneath the hellish assault.

So, if a bunch of closed doors in murky, unbreathable air is your idea of a good time, let's go.

Reeking, foul, unbreathable air closed about them like a wave.

Cordite, muzzle smoke and plaster haze making the air almost unbreathable.