Residents could live, work and sleep inside the pressurised tubes with no need for space suits and with plenty of spare real estate for some low-gravity recreation.
The idea is to pressurise the carbon dioxide so that it becomes a liquid. The fluid is then released into the dishwasher where it cleans the dishes all by itself.
Rather than simply situating a Moon base inside a lava tube—domes and shiny buildings and all—they suggested that a section of such a tube could be pressurised with breathable air.