What type of burn occurs with insufficient air in gas appliances?

The presence of a sooty or yellow flame in gas appliances is indicative of incomplete combustion, which occurs when there is insufficient air supply. In a properly functioning gas appliance, complete combustion should produce a blue flame, which signifies that the gas is burning efficiently with enough oxygen. However, when air supply is restricted, the fuel does not undergo complete combustion, resulting in the formation of soot and a yellow or orange flame. This is not only a sign of inefficiency but also poses dangers such as increased production of carbon monoxide and reduced appliance performance.

The yellow, sooty flame is a clear warning sign that maintenance may be necessary, as it indicates that the appliance is not operating as it should be, and adjustments may be needed to ensure a balanced mix of gas and air for safe and efficient operation.