Direct Fired Thermal Desorption (DFTD) consists of a counter flow desorber drum and attendant air pollution control equipment. The rotary drum desorber operates the flow of soil counter to the flow of combustion gases. This counter-current and or parallel flow system provides highly efficient heat transfer and flue gas temperature control.

As the drum rotates, fighting along the drum's interior surface it lifts the soil and drops it in a succession of thin "veils,“ exposing the surface of the soil particles to the stratified temperature profile in the drum maximizing heat transfer. Water is sprayed as materials exit the soil conditioner. The water is utilized to cool the materials and knock down any dust.