What is a Sooty and Non-Sooty Flame?

Unsaturated carbon compounds do not tend to burn completely. Also, they give flame with those carbon particles that are not burnt or partially burnt. Such flame is yellow in color and tends to pollute. 

This is known as a sooty flame. On the other hand, saturated carbon compounds tend to burn completely. Along with this, they give a clear flame that is blue in colour. This is known to be a non-sooty flame. Therefore, the colour difference between sooty flame and non-sooty flame gives them the required recognition.