At 5 p.m., an explosion and fire occurred during repair works in an ethylene oxide/glycol unit of a petrochemical industry. The metal covering of the insulation of a distillation column (K-303, operating at 60°C under 3 bar and containing mainly ethylene oxide) was being removed in order to repair a level indicator. Ethylene oxide had leaked through a hair-crack (created by low cycle fatigue) in a weld of the column and accumulated in the rock-wool insulation of the level indicator, where it had reacted with moisture to form non-volatile polyethylene glycols (PEG). Hence, upon opening of the insulation, air leaked into the insulation material soaked with PEG, causing its decomposition and initiating auto-oxidation. The insulation ignited and the resulting heat flux caused the ethylene oxide to decompose (VCE) and thus the explosion of the column. The gas line between the head of the column and a following purification column (K-302) was torn off and the escaping gas caught fire. Flames backed into the K-302 column and caused an internal explosion 26 s after the first one. Impacts from debris of the 2 explosions caused damage in other sections (incl. the recycle gas loop) of the ethylene oxide/glycol installation which in turn fuelled a huge fire (domino effect). Both columns were automatically isolated and technicians manually cut-off the energies of the installation. The plant fire fighting team was able to confine the fire and to put it under control in less than one hour. The city fire brigade arrived on the scene but did not intervene. 5 employees suffered minor injuries. The cost of the material damages were estimated at 0,05 MECU. No effect was reported outside of the establishment. The authorities underlined an inadequate process analysis, plant design and inspection procedures. Following measures were taken : 1- use of a non-absorbing insulation material with a small specific surface area; 2- in-depth inspection for leaks and also for the possible existence of any accumulation of polyethylene glycols (PEG); 3- inertization of parts of the equipment where stagnant zones of ethylene oxide/water mixtures may be created (e.g. instrumentation stand pipes) by means of continuous nitrogen purging.