[2/7] The decree only speaks of odours. The importance of the olfactory sense had its origins in the miasma theory of Hippocrates of Kos, which was received well into the 19th century. The hygienists of the Enlightenment also assumed that the slow decomposition of organic substances released foul odours/miasmas that led to disease. There was hardly any experience of modern industrial plants around 1800, medical science was not yet professionalised and there were no chemical detection methods or the idea of clinical studies to determine thresholds. Such plants could therefore only be tested for harmfulness on the basis of subjective perception, primarily through the olfactory sense.

[3/7] In her study on environmental conflicts in Aachen and Duisburg during early and high industrialisation, Stephanie Geissler was able to prove that sensory perceptions were one of the main arguments used to assess the potential harmfulness of industrial plants, both in residents' complaints and in official inspections.
Geissler, Stephanie, Wem gehört die Stadt? Umweltkonflikte im städtischen Raum zur Zeit der Früh- und Hochindustrialisierung in Aachen und Duisburg. Münster 2016

[4/7] An effective remedy was soon found for the miasmas: Acid gases. According to contemporary chemists, these were supposed to neutralise miasmas. One of the best-known advocates was Louis-Bernard Guyton de Morveau, whose work Traité des moyens de désinfecter l'air was translated into various languages - including German by Franz-Heinrich Martens - and was disseminated within France by the then French Minister of the Interior Jean-Antoine Chaptal.

[5/7] Acid gases from chemical factories were therefore supposed to neutralise miasmas. What could be more obvious than to build these factories in cities where diseases were more common? Samuel Hahnemann, the founder of homeopathy, also believed that inhaling acidic vapours was healthy. Of course, there were also dissenting voices. But what chance did they have of being heard when the French Minister of the Interior and the majority of the Académie des sciences considered acid gases to be the medical discovery of the century? The minister of the Interior Chaptal, himself a chemist, played a significant role in the genesis of the 1810 decree. He himself was the owner of chemical factories with acidic vapours. Honi soit qui mal y pense...

[6/7] Of course, unless you have a medium or a necromancer at hand, it's hard to say whether Chaptal was pursuing economic interests alone or was convinced by the prevailing opinion on acid gases. It was probably a bit of both. But even he could not prevent the increasing complaints against factories. His successor as Minister of the Interior was therefore forced to commission a report to analyse the harmfulness and countermeasures of such factories. Chaptal was able to use his influence in the Académie des sciences, most of whose members were already in favour of the disinfection theory, to declare chemical factories harmless and combined this judgement with a warning. If the expansion of factories were hindered by laws or regulations, nobody would invest in the industry any more. One might think that sounds somewhat familiar...

[7/7] The Continental Blockade of 1809 made the situation even worse. Soda factories in particular caused immense damage to vegetation. The Minister of the Interior demanded a new report, but one that was more balanced. Ultimately, this formed the basis for the decree of 15 October 1810.
In addition to the debate about miasmas and their disinfection by factories, as well as the consequences of this, another argument tangential to the intrinsic values of the revolution played an important role: the protection of private property...