Abstract: A supervisor and another employee were unplugging a line containing fly ash. They were standing on top of a tank used to collect the fly ash from three hoppers located above them. When the clog suddenly let go, the economizer tank could not handle the sudden flow of fly ash, and an unsecured tank cover and the water gasket blew out. The employees were showered with hot fly ash from the hoppers. Both employees were burned, and one of them was hospitalized for his injuries. The employees had not closed the valves leading from the hoppers, had no job briefing, and were not wearing appropriate personal protective equipment. Additionally, the employer did not have a documented procedure for performing the unplugging, though it was a common occurrence.