Abstract: A process and apparatus are provided for pyrolysis cleaning of residues from equipment used in the treatment and processing of synthetic materials, particularly synthetic plastics. The process comprises a first stage in which the equipment to be cleaned is heated in a closed chamber in the absence of air at a temperature above the melting point of the synthetic material from which the residue is left, and a second stage in which the equipment is heated at a higher temperature in the presence of air. The apparatus preferably comprises a slightly inclined, substantially horizontal heating chamber including a drain at the lower end for collecting melted residue, a vent for gases distilled from the residue with means for burning such gases, and an air inlet for introducing air to the chamber during the second stage.