In a fine chemistry unit, the temperature of a reactor abnormally surged (tripping the alarm) during the casting of an aldehyde-phenol compound into a mix of hydrogen peroxide, maleic anhydride, methylene chloride and dimethylformamide. The technician shut down the metering pump and closed the aldehyde tank valve. The reaction began to run away at 11:16 am before being flooded by a water intake. A rupture disc and the unit’s glass enclosure and windows shattered. No victims were reported and no environmental degradation detected. Upon turning off the temperature alarm at 10:03 am, the technician inadvertently stopped a stirrer. The operating protocol and faulty instrumentation were not compliant with the unit’s safety report.