coals whose properties are often far removed from the coals specified for the original boiler design. The changing electricity market in many areas where the use of fuels other than coal (for example gas) has become widespread, has led to coal-fired plant being operated in some regions (for example OECD countries) under regimes other than base load. This change in operation has helped to reduce boiler slagging to some degree through the regular shedding of deposits as the boiler is thermally cycled.