The life of ten million souls beneath the mountain depended entirely upon the unseen breath flow of air.
Deep within the central stone-built tier of the Hall of Ten Thousand Statues, Entry hall 042 served as the lungs of the safe hall. Here, sixty huge upright air-flow chimney pipes, each twelve arm-lengths in width and bored through solid granite during the elder epoch, reached up to the high crags of the mountain’s northern face. Through these shafts, the natural heat draft created by the earth-heat drain pits drew cool, crisp sea breezes downward, filtering the air through porous beds of calc-spar and crushed foam-stone before circulating it through the Eighty Barren Courtyards.
The stonework of the chimney pipe array was a triumph of ancient air-powered design. Each upright channel was fitted with spiral banded limestone baffles that caught drifting salt spray and sky soot. It allowed only dry, oxygenated air to go down into the lower arcades. At the base of each shaft stood counterweighted balancing vanes carved from dense river shale, which swung open or shut in response to external air-pressure shifts. It maintained an unvarying air pressure throughout the deep residential quarters.
If these chimney pipes were fouled, the safe hall would become an unbreathable tomb within six watches.
