These underground rooms are specialized ceremonial areas known as kivas. They are still in use in modern pueblos. They contain a fairly efficient ventilation system - a ventilator shaft opening into the room at floor level, a low masonry deflector wall between the shaft and the firepit, and the opening directly above the fire hearth. These features can be found in prehistoric ruins dating back almost 2000 years in the American southwest.

Some kivas with intact roofs are known, as well as habitation rooms with firepits and intact roofs. What is interesting is the massive quantities of soot deposited on the roof beams. Air quality must have been pretty bad at times, but people probably did not spend a great deal of time within these rooms. No idea what the CO levels would have been. Some things are just beyond the archaeologist's knowledge....