Natural draft appliances rely on which mechanism to move combustion air and exhaust gases?

Natural draft appliances rely on which mechanism to move combustion air and exhaust gases?

• A. Sealed combustion with outside air
• B. Natural convection
• C. Forced induction through a blower
• D. Mechanical ventilation with fans

Answer: (B)

Natural draft relies on buoyancy-driven convection. When the burner fires, the combustion gases heat up and become lighter than the surrounding air, so they rise up the vertical vent. That upward movement creates a draft that draws cooler air into the burner for combustion and pushes the exhaust out through the chimney. No fans or blowers are used, and the strength of the draft depends on vent height and the temperature difference. If the vent is blocked or too cold, the draft weakens and can cause issues like backdraft or incomplete combustion. The other options involve mechanical devices or sealed designs, which are not the mechanism at play here.

Natural draft relies on buoyancy-driven convection. When the burner fires, the combustion gases heat up and become lighter than the surrounding air, so they rise up the vertical vent. That upward movement creates a draft that draws cooler air into the burner for combustion and pushes the exhaust out through the chimney. No fans or blowers are used, and the strength of the draft depends on vent height and the temperature difference. If the vent is blocked or too cold, the draft weakens and can cause issues like backdraft or incomplete combustion. The other options involve mechanical devices or sealed designs, which are not the mechanism at play here.