When you have an open flame on a burner, it is typically fueled by a gas like propane or natural gas. The flame is created by the combustion of this fuel with oxygen from the surrounding air. During combustion, the fuel (propane) and oxygen react chemically, producing heat, light, water vapor, carbon dioxide, and other combustion by-products.
If the fuel supply is suddenly cut off or depleted, the combustion process will cease, and the flame will extinguish. There are a few reasons why smoke doesn't come out of the burner when the fuel is no longer being used up:
Combustion stops: When the fuel supply is cut off, there is no longer any fuel available to burn. Combustion requires a continuous supply of fuel and oxygen, and without fuel, the reaction cannot continue, causing the flame to go out.
Incomplete combustion: In a well-regulated gas burner, the combustion process is optimized to produce a clean, blue flame. This indicates efficient and complete combustion, where the fuel is almost entirely converted into water vapor and carbon dioxide. When the fuel supply is suddenly stopped, the flame doesn't have a chance to produce smoke because it's designed to burn cleanly with minimal soot or other by-products.
Limited oxygen: In a controlled gas burner, the air intake is carefully adjusted to provide the right amount of oxygen for complete combustion. When the fuel supply is cut off, there might still be some residual oxygen available near the flame, but it quickly dissipates due to convection and diffusion. Without sufficient oxygen, the flame cannot sustain itself, preventing the production of visible smoke.
Short-lived by-products: Even during normal combustion, any smoke or visible by-products are usually short-lived and quickly dissipate due to the heat and airflow around the flame. These by-products are often very light particles that rise and disperse rapidly, making them hard to notice in well-ventilated spaces.
It's important to note that if you notice any smoke or unusual behavior from a gas burner, it might be a sign of a malfunctioning burner or inadequate ventilation. In such cases, it's essential to turn off the gas supply and seek professional assistance to ensure safety.