What is a B Vent or Natural Draft Gas Fireplace?

A natural draft gas fireplace DOES NOT HAVE a sealed chamber (where combustion takes place). Instead it relies on the buoyancy of hot gases to vent. It is important for these vent applications to be installed with an existing chimney that meets local building code or by using a B vent. A  B vent is a pipe that is installed using the same procedures of a masonry chimney, but can be enclosed in a combustible material. Since the flue gases are hot and rise naturally, oxygen needed for combustion draws easily from the surrounding area of the fireplace. This creates a simple route for the gases to go up through the chimney. In turn, as the fireplace is used and the hot gases travel upwards, the walls of the chimney heat up, and retain their temperature and buoyancy, creating a faster speed with which the flue gases exit the chimney.