More dangerous still is the threat of a crown-sheet explosion, caused by inattentiveness or lack of training or experience. If a fireman lets the water level get too low, and then corrects the problem by injecting feedwater on the exposed metal, the result is a flash steaming which raises the backhead pressure beyond the firebox' ability to cope—the inevitable result is the scalding death of the culprit and his engineer, and cartwheeling of the torn-free boiler ahead or above the disabled locomotive.