Question

what does this statement mean
as if from some enormous furnace from which it could draw at will.

Answer 1

Answer:

What does a gas furnace look like? Indoor unit (gas furnace for heating + A/C coil on top for cooling) is located in the basement, closet or attic and looks like this: Two thick white pipes are for intake and exhaust of air; they are typical for high-efficiency furnaces (90%+ efficiency).