G2 Gas Fitter Practice Exam

Draft caused by the pressure difference of hot gases rising in a chimney is called?

1. Mechanical draft

2. Naturally induced draft

3. Forced draft

4. Natural thermal draft

The correct answer is: Natural thermal draft

The phenomenon where the pressure difference created by hot gases rising within a chimney generates a draft is accurately described as natural thermal draft. This process leverages the principle of convection, where warmer gases, being less dense, rise and create a pressure difference relatively to the cooler surrounding air. As the hot gases exit the chimney, this reduction in pressure inside facilitates the entry of fresh air into the combustion area, enhancing the efficiency of the burning process. Natural thermal draft harnesses natural forces without the need for any mechanical assistance or external devices, distinguishing it from mechanical draft or forced draft systems, which rely on fans or blowers to induce airflow. In contrast, while naturally induced draft might convey similar meanings, it is less specific in describing the underlying thermal aspect that drives the draft in chimneys due to rising hot gases.