Recently, Museum Boerhaave acquired a set of air pollution monitors, which were used in the 1970s and 1980s in the national measuring network for air population, which covered the whole area of the Netherlands. The monitors, made by Philips, show a notable technical evolution. Whereas the first types worked according to chemical detection principles, the subsequent generations consisted of electronic detection cells. Yet, what make the instruments particularly interesting is that they can be regarded as artefacts that reflect the large social concern with air pollution in the 1970s and 1980s (especially acid rain). From the point of view of the history of scientific instruments, the monitors make an interesting case because they belong to a category of instruments that have not received much attention so far: scientific instruments devised specifically to protect human beings.