In an chemical industry, an unexpected acetylene decomposition happened during the vinylation of cyclohexanol with acetylene in vinylcyclohexylether. The acetylene decomposition do not caused the necessary pressure rise to trigger the emergency shut-down which is rebounded in the low pressure. The pressure rise caused the rip-off of a valve that was followed by a jet-fire in the compressor hall of a vinyl esthers production plant. No people were. Following the accident, the control and measurement technique have to be improved.