What is the nature of the vents installed in the side of this chimney?
a. They serve direct vent heating appliances installed in fireplaces on the first and second floors.
b. They serve the same purpose as a draft diverter, accelerating rising exhaust gasses and helping to prevent backdrafts from wind gusting.
c. They are intakes and supply combustion air for wood-burning fireplaces installed on the first and second floors.
d. They are dampers designed to automatically bleed off excess heat from high-performance wood stoves. Excessive heat can damage the catalytic converters in these stoves.