Air exchange rate ‐ the dominant parameter for preventive conservation?

Abstract This article aims to demonstrate that air exchange rate is extremely important for the performance of display cases with regards to relative humidity buffering, dust and pollutant ingress and corrosion of metals displayed within them. The display cases built for English Heritage to house the Wernher Collection of small and precious objects at Ranger's House, London are investigated. The displays were set up four years ago, and air exchange rates were measured and leakage rates reduced as far as possible at that time. The extended methods for measuring air exchange rates are discussed and the longer term performance of the cases is investigated. The importance of the capacity of the cases to maintain appropriate RH levels without using the hygroscopic objects to act as buffers is also highlighted. Maintenance of display case performance requires monitoring, actions and effort, as seals and mechanical parts age.

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