Service life refers to the period of operation over which a catalyst delivers its guaranteed cleaning performance without having to be replaced. Under optimum conditions, i.e. in the absence of catalyst poisons and within the specified temperature window, the service life of modern industrial catalysts is typically between 5 and 10 years. Service life depends heavily on chemical load and thermal stress. Regular performance tests make it possible to monitor the deactivation process and to plan replacement. Since the catalyst is a significant cost factor, a long service life represents a direct economic advantage. Professional maintenance and, where appropriate, thermal regeneration can often extend the service life significantly.