Diffusion flames occur when fuel and oxidizer mix in the air before combustion. In this type of flame, the fuel vaporizes and diffuses into the surrounding air, where it reacts with oxygen to produce heat and light. This process is common in everyday situations, such as in a candle flame or a gas stove. These flames are characterized by their yellow or orange color, which results from the presence of tiny soot particles that glow when heated. Diffusion flames are typically less efficient than other types of flames, such as premixed flames, because the mixing of fuel and oxidizer happens after they are already separated.