An afterburner is generally made of a steel shell lined with refractory materials such as firebrick. The refractory lining saves the steel shell and acts as a thermal insulator. When enough time and high enough temperatures are used, gaseous organic pollutants get completely oxidized, with an incineration efficiency approaching near 100 %.
To get complete combustion of the VOCs and other hydrcarbons, the afterburner must offer the proper amount of turbulence and burning time, and it must also maintain high enough temperature.
Afterburners are generally used to control odours, destroy toxic compounds, or reduce the amount of photochemically reactive substances released into the air.