If the purging process calls for changes in system temperatures, great care is needed if the production material is heat-sensitive. You could degrade residual production resin and badly contaminate the system with carbonized material.
Materials with limited margins between processing temperatures and critical temperatures – such as PVC, acetals, barrier resins and elastomers – must be removed from the system, either by effective flushing or pre-purging at operating temperature, before increasing heat to address purging requirements.