The build-up of ash may grow to several feet, leading to deposits of tons of fly on the boiler roof. Over the time, this weight on the building structure may result in metallurgical strain, which in rare case might lead to boiler collapse.

The uncooled construction parts such as rods and hangers can get overheated with the insulating properties of fly ash.

The cooling down time of fly ash is very high and it usually takes one week. This leads to delay in other maintenance activity every time. Moreover, the bypass of flue gas into the upper dead space of boiler environment reduces combustion efficiency.