A butadiene leak occurred inside a chemical plant; its origin was a flare pipe break on a butadiene workshop reboiler. The gas alarm was immediately activated as was the internal emergency plan. 7 tonnes of butadiene escaped, a vehicle crossing the butadiene spill felt the impact: the butadiene saturation was so high that the vehicle stalled due to a lack of oxygen. As an emergency measure, the workshop was shut down and personnel applied safe operating principles by lowering the pressure on equipment using a flare. The sector was isolated, and the company’s first response team immediately set up water curtains around the leak. Vehicle traffic was blocked and plant staff kept indoors. The leaking line was isolated after some 25 min and the internal emergency plan lifted 10 min later. No injuries were reported and property damage remained limited. The D51 column in the butadiene unit contained two reboilers and a reflux drum. Under normal operating conditions, just one reboiler would have been left on. The suspect reboiler had not been placed in service; moreover, it had been connected to the column by a line featuring a tap leading to its safety valve. This line, on which no product flux had been circulating, constituted a cut-off where polymers formed (popcorn production); it was the accumulation of such polymers that caused the pipe to burst. Following this accident, popcorn was discovered at 4 other places; the dubious cut-off was eliminated and the slope of the line modified (turning vertical to avoid popcorn accumulation). Another column was modified similarly, while the other two columns (which could not be altered) underwent quarterly radiographic monitoring. In order to avoid oxygen intake via the manholes on column D51, the holes were fitted with double-plated spans. The space lying between these plates was inerted. Eight manholes were treated this way. Before service restart, the column, reboilers and reflux drum were all passivated to eliminate any point of rust capable of stimulating popcorn formation. The idle reboiler was also plated and inerted. A tap was created to allow injecting an inhibitor into the circuit containing the 2 modified columns. No influence was detected regarding the butadiene stemming from the group’s other sites.