Six-inch type “B” vent chimney, which is the most common in the U.S., requires about 90 Btu per foot for a temperature rise from zero degrees to 120°. Thus, on a very cold day, 55 feet of Type B ...

ADEAR SLADE: The place to check for carbon monoxide is not inside the flue pipe. ... If the installation violates local code, the builder should install a vent to the outside.