There were rows of houses which were built back to back with only one door with no other ventilation. The only time the stale air escaped the house was when the fire happened to be burning and thus the stale air could escape through the chimney.
Maintenance of the houses (rather the lack of it) was the key issue. These houses were not so bad when they were newly built but they were never repaired. The people who built these houses saw the venture as an investment for twenty to forty years. They argued that repair would diminish their income.
Moreover, these buildings were built on leased land and therefore nobody had any stake in them.
During the last ten years of the life of the house the inhabitants used up the woodwork for firing.