Organic materials in museums and collections are susceptible to deterioration in the presence of oxygen. E.g. Oxygen reacts with parchment (made from animal skin) and with some of the materials present in mummies over long periods of time; it changes their chemical composition and, subsequently, their physical properties. Thus, the preservation of these objects is aided by excluding oxygen from museum cases in which they are displayed or stored. A reduction of the oxygen concentration to the lowest that can be achieved, preferably below 1000 ppm, is disired. This is achieved with blanketing, also known as inerting, the process of injecting an inert gas into the cases or space where artefacts are stored. To maintain the preferred low oxygen levels oxygen transmitters or analyzers are used.