A foreman and operators reviewed the drum temperature sensors and concluded that the drum contents had sufficiently cooled to un-head. The top head of Drum A was removed without incident or any further indication of the temperature of the coke at bottom of Drum A. Using hydraulic controls, employees lower the bottom head of the vessel. In a matter of six seconds, 46,000 gallons of coke, still at auto-ignition temperature, spewed out in all directions from the bottom of the drum. The coke ignited, engulfing six observers and standby workers in flames.