A Type B or Type L gas vent must terminate at least 5 feet in vertical height above the highest connected appliance’s draft hood or flue collar. A Type B-W gas vent must terminate at least 12 feet in vertical height above the bottom of the wall furnace.
Gas vents shall extend through the roof flashing, roof jack, or thimble, and terminate with a listed cap or assembly.
Type B vents are vents suitable only for listed, draft hood-equipped, gas-fired appliances, including most domestic heating and hot water systems.
They may not be used with any of the following appliances:
- wood-burning appliances, such as fireplaces and wood-burning stoves;
- oil-fired equipment;
- coal-fired equipment;
- any appliance that burns anything other than liquid petroleum or natural gas; or
- any appliance that produces flue gases that exceed 480° F (249° C).
Type B vents must be equipped with their own special chimney caps. If the cap is damaged or lost, it should not be substituted with something not recommended by the manufacturer. The clearance required from combustible materials is printed on the flue’s exterior metal surface, and is generally 1 or 2 inches.
Chimneys should extend at least 2 feet higher than any portion of a building within 10 feet, but shall not be less than 3 feet above the highest point where the chimney passes through the roof. This, again, is known as the Chimney 3-2-10 Rule.
This is straight from the Course.
I had to look it up!