Around 1801 Louis-Bernard Guyton de Morveau (1737–1816) designed his famous fumigating machine. The machine spread a controlled emission of a specific gas—described as an oxygenated acid—that was supposed to destroy the contagious miasmas in the air, objects, and bodies. During the 1804 outburst of the yellow fever, the Spanish Government ordered that the original design of Guyton’s fumigating machine be adapted to the Spanish market for extensive use in households. This was done against some criticism, as the nature of the contagion was avowedly unknown and the acid fumigation technology polemic. Nonetheless, the machine was pictured as crucial for the health of individuals and for society as a whole. The essay looks at the fumigating machine as a way of exploring how scientific and political practices pervaded societies and, vice-versa, how ways of interpreting nature and politics became embedded in artifacts. It will show, first, how the machine served to spread the new French chemistry among Spaniards; second, how it embodied a new relationship between the citizens and the state, and third, how this artefact was imported by the Spanish absolutist state, appropriated, and used for political propaganda. By focusing on a chemical artefact, it shows a historically complex and significant interweaving of theory, material culture, and politics.