smoke hole/vent
Bob I realize that you did your adventure in 1988. You make a point though. The heat you experienced was likely built up carbon dioxide. But for anyone else wanting to attempt to build or stay in an igloo please do the smokehole vent. That vent is essential to not only let smoke escape but also let in oxygen. Without it carbon dioxide (a heavier gas) will settle to the floor area. In extreme circumstances it will cause headaches and can silently suffocate animals and kids who dwell on the floor. There is a place in Africa near carbon dioxide releasing lakes Mynoun and Nyos where animals decend into a natural bowl to get water and are trapped by the lack of oxygen. They enter, can't breathe and fail to understand that they need to exit the depression. If they don't (sometimes only a vertical distance of four or five feet) they are asphyxiated. Days later when breezes sweep the bowl no one could determine why the animals died. VENT!