Text 4 Luminous Flames and Non-Luminous Flames

A luminous flame occurs when there is a limited supply of oxygen during burning. This results in incomplete combustion, which forms soot, carbon monoxide, as well as carbon dioxide that is the main gas formed. The soot is pure carbon, and causes the blackening of lampshades or the bottom of pans. Carbon monoxide is a toxic gas. It is dangerous because it bonds with haemoglobin in the blood, preventing it from transporting oxygen to the cells in the body. If carbon monoxide poisoning is not treated immediately, it will result in death. A luminous flame is a large, bright yellow flame, which generally burns unsteadily. Also, as the name suggests, the luminous flame gives out light. This is because the tiny particles of carbon soot glow when they get very hot. These flames are common in a burning candle, a gas lamp, or a Bunsen burner when the air hole is closed.

Non-luminous flames occur when there is an abundant supply of oxygen, which results in complete combustion. The main product of complete combustion is carbon dioxide. No carbon monoxide or soot is formed. The non-luminous flame does not give out much light since it contains no carbon which can get hot. These flames have a characteristic blue colour and burn steadily. They give out a roaring sound and so are also known as “roaring” flames. Non-luminous flames can be observed when the burners of a gas-stove are lit, or when the air hole of a lit Bunsen burner is open.