The alarm did not sound as a siren. It arrived as a bitter, greasy smell that crept through the air-flow chimney pipes of Entry hall 029.
In the middle of the morning watch, when seventy thousand mothers and children were resting upon the fourth cut stone terrace, the fresh draft flowing from the ceiling chimney pipes suddenly turned acrid. It carried the heavy, choking reek of burning sheep fat and raw seal blubber—foul, fatty combustibles salvaged from the sunken supply barges.
Within minutes, coughing erupted along the eastern terraces. Infants awoke, wailing in distress as a sluggish grey smoke began to pool beneath the vaulted ceiling. The porous banded limestone of the high vaults, which naturally absorbed and exhaled sky humidity through millions of tiny blood vessel pores, was being coated in a sticky film of greasy black soot.
Qiao Ming was surveying the drainage channels of Entry hall 031 when his nostrils caught the tainted draft. He dropped his horn measuring gauge, took the Folded brass star-compass from his chest harness, and unfolded its heat sense vanes.
The tracking data showed an immediate drop in local air permeability. The tiny blood vessel pores of Chimney pipe 029 were choking, their natural gas-exchange rate dropping precipitously under the soot deposit.
