"Air shafts, allowing air or escape to the surface, was not built
into this system due to the Mars atmosphere outside. Instead, safe rooms, oxygen access points or escape sets, and ventilation piping throughout the tunnel were installed every thirty feet or nine meters along the tunnel’s walls."
"The running tunnel design had been opened up to allow space
below the Interview Room to retract if need be. Ahmans and humans worked together, still in their atmospheric suits, to place wiring, lights, sewer connections and communication devices throughout the tunnels. The height of the passageway grew to twenty feet. The walls were then cladded with a mixture of polypropylene plastic and Mars cement from heating the frozen soil and setting
concrete, an accelerator recipe the ahmans gladly shared.