A retrofit refers to the technical upgrade or conversion of an existing exhaust gas cleaning system, often a thermal oxidiser (thermal afterburner), to the catalytic process. Since the housing and peripheral equipment can often continue to be used, a retrofit is a cost-efficient way of drastically reducing the operating costs of an older system. Installing catalyst modules lowers the required operating temperature from approx. 800 °C to around 300 °C, which saves enormous amounts of heating energy. A retrofit is often carried out in response to stricter environmental regulations or rising energy prices and offers a fast payback with minimal construction work.