The surface of the steel was still covered, after they had cleared it as much as they could, with a thin, clinging coat of plaster which might well conceal the button or device for opening the door.

Every moment the task became infinitely harder.
Finally Jerry, his lungs nearly empty of oxygen, cast himself down on the floor and gasped.

A horrible gagging sound betrayed his efforts for breath.
Ronicky knelt beside him.

His own lungs were burning, and his head was thick and dizzy.

"One more try, then we'll turn and rush them and die fighting, Jerry." The other nodded and started to his feet.