At the top of the stairs is a hallway going to the right, with a small room on the other side of it. This room contained the heater which provided water for the radiators. The hole in the ceiling is an 8 inch vent pipe through the roof. Because the hot water circulation system is a closed loop no contaminates would get into the GPMTCP, and the heater could be outside the gas protected area so that they didn't need to filter the combustion air. Putting the heater insdie the gas protected area would have required a lot more air flow, meaning a much larger filtration system.

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