Passive Anoxic Display Cases
Passive oxygen free display systems utilize extremely well-sealed enclosures, with every possible measure taken to prevent leakage. Oxygen levels must be kept very low to prevent artefacts reacting with residual atmospheric oxygen. Even a tiny hole or path through the gasketing or envelope may be enough to spoil the integrity of the showcase, making it ineffective. Oxygen can also permeate and pass through many of the materials that might be used to create or seal the showcase, so all the materials to be used in the construction of an anoxic case must be carefully considered.
In a passive anoxic display system, oxygen absorbers are used to absorb any oxygen that might penetrate the showcase. Humidity control is also accomplished using passive buffering, such as PROSorb. Pollution scavengers are often added. Systems for purging the showcase, equalizing atmospheric pressures, and testing levels of oxygen and humidity must also be provided.
A passive system must be carefully monitored and maintained, but maintenance can be minimal if the showcase is well-designed. The construction and sealing of an anoxic showcase are painstaking operations, and techniques and construction materials may both limit aesthetic considerations and extend timelines.