Section 10.1.1/Venting of Gas Appliances
NFPA 54 Chapter 10 covers vent sizing, materials, termination heights, common venting, and connector requirements for gas appliances.
Gas-fired appliances that are not direct-vent or power-vented must be connected to a vent system that carries combustion products to the outdoors. Natural draft vents (Type B for gas appliances) must be sized per the vent tables in Chapter 10 based on the appliance input rating, vent height, vent connector length, and number of elbows. When multiple appliances share a common vent, the vent must be sized for the combined input. The vent must terminate above the roof at the height specified in Table 10.5.2.2 based on the roof slope. Vent connectors (the horizontal run from the appliance to the vertical vent) must slope upward at least 1/4 inch per foot toward the vent.
Why this section exists
Combustion products from gas appliances contain carbon monoxide, water vapor, and nitrogen oxides. These products must be vented to the outdoors to prevent carbon monoxide poisoning and moisture damage inside the building. An undersized vent cannot develop adequate natural draft, causing combustion products to spill into the occupied space. A vent that terminates too low can allow wind to force combustion products back down the vent. Proper venting is critical to occupant safety.
What plan reviewers look for
Plan reviewers check the mechanical drawings for vent sizing at each gas appliance. They verify the vent size against the Chapter 10 tables for the appliance input, vent height, and connector configuration. They check the vent termination height above the roof. For common vents serving multiple appliances, they verify the combined sizing. They check that vent connectors slope upward toward the vent. They verify the vent material (Type B, Type BW, or listed chimney liner) matches the appliance requirements.