Gas Fitter Practice Test

What could a continuous yellow flame indicate in a combustion process?

1. A. Adequate gas pressure

2. B. Insufficient air supply

3. C. High furnace efficiency

4. D. Proper pilot function

The correct answer is: B. Insufficient air supply

A continuous yellow flame during a combustion process typically indicates that there is insufficient air supply for complete combustion. When a fuel gas burns with an inadequate amount of oxygen, it produces a yellow flame due to the presence of unburned carbon particles in the flame, also known as soot. This incomplete combustion causes the flame to burn cooler and can lead to several issues, such as the production of carbon monoxide, decreased efficiency, and potential damage to the appliance. In contrast, an adequate gas pressure would typically produce a blue flame, indicating efficient combustion with the proper mix of gas and air. High furnace efficiency is also characterized by a blue flame, which reflects complete combustion. Proper pilot function would ensure a consistent flame, generally blue in color, indicating appropriate air and gas mixture. Therefore, recognizing the characteristics of a continuous yellow flame is crucial for gas fitters in diagnosing combustion-related issues and ensuring safety and efficiency in gas appliances.