It is not constituent of coal but consists of a complex mixture of gaseous and liquid products due to thermal decomposition of coal substance.
High volatile matter containing coal burns with a long flame, high smoke (pollutes air) and has low heating / colourific value. So lesser the percentage of the volatile matter better is the quality of the coal.
Low volatile matter containing coal has good caking property.
It forms hard and strong coke on carbonization. It also yields coke oven gas which is a source of many chemicals.
Medium volatile matter containing coal has good caking property. It forms hard and strong coke on carbonization, it also yields coke oven gas which is a source of many chemicals.
High volatile matter containing coal is used for coal gas production as the volatile matter is converted to gas and tar products by heat.
High volatile matter burns with long and smoky flame but those having low volatile matter burns with shorter and clean flame.
So, higher the volatile matter content the larger is the combustion space required in the furnace.
Hence, the volatile matter content of coal influences the furnace design.