On 31st August 1794 at 7:15 am, either 30.2 tonnes (65,000 pounds) or 150 tonnes of powder (depending on the source) exploded in the gunpowder storage room at the Château de Grenelle, near the Military School (Ecole militaire), in a heavily urbanized zone of Paris. The 2,000 workers cramped into the workshop were producing black powder in an overheated atmosphere without taking any protective measures. The recent working methods implemented had made it possible to increase production capacity. Consequences of this accident were tremendous: 1,000 victims were counted among the plant’s personnel and neighbouring residents, along with the complete destruction of buildings, nearby dwellings and trees. The origin, despite being widely attributed to a malicious act, in fact remained undetermined. The rescue of the injured and rebuilding of homes gave rise to an outpouring of solidarity among the Paris population and adjoining municipalities. The rise in awareness of technological risks stimulated by this disaster is considered as having launched France’s industrial safety regulations with the 1810 Imperial Decree on hazardous, squalid and dilapidated installations.