On the morning of January 21, 2013, the Lubrizol plant in Rouen released mercaptan fumes. The resulting plume drifted over the departments of Seine-Maritime and Eure, as well as over departments in the Île-de-France and Champagne-Ardenne regions during the night of January 21–22. Mercaptans, highly odorous markers used to add a smell to city gas, led to numerous complaints from local residents regarding unpleasant odors.