Old house chimneys
Neighbor and I live in houses built in 1919 for working class people. We are trying to figure out the chimneys and fireplaces, two over two in each house, all sealed over. He is renovating a bedroom above the dining room and found solid brick behind the mantle. There are two round holes. The one on the lower left opens to a small box that appears to vent up one side of the double chimney. He has not opened the upper one yet.
Can anyone give us insight into what went on here? His house had an oil furnace at one point.