On of the most serious diseases which attacked Europe in the 19th c. was cholera. The 19th c. saw five pandemics which reduced the world population by 30 to 40 million people. Before vibrio cholerae was isolated by Robert Koch in 1883, doctors had not known the source of infection and had applied the means of treatment and prevention which were commonly used in the case of other contagious diseases. The article describes the method of purifying the air during an epidemics called fumigation. Interiors were fumigated with the fumes of natural substances (juniper, vinegar or even animal manure) or chemicals (calcium chloride). The former were easily available in any household; the latter could be bought at the chemist's. Calcium chloride was dispensed free of charge. Fumigation was recommended in official documents, although its effectiveness was generally doubted. Moreover, the fumes of vinegar or calcium chloride irritated the eyes and throats. Nevertheless, fumigation was applied almost until the end of the 19th c.