Well sealed display space for museum display cases,museum showcases
Air change is defined as the ratio of air supply into a display space in relation to the volume of display space.Air exchange rate (AER) or leakage rate of display cases dictates the flow of air (a mixture of gases including water vapour, pollutants and particulates) in and out of internal display space.The air exchange rate will effectively influence the display space of display cases to buffer external environmental conditions and limit the ingress of dust and externally generated pollutants.In addition,the finally acquired micro-climate values and the control precision of climate system are also very related to the airtightness of display space.
Well airtightness is achieved by consistency of display cases' structure, the high fabrication precision for each parts, the dedicated sealing aluminum-alloy extrusions,the glass bonding technology,the door sealing strips and the performance of opening system.Integrated well airtightness of museum display cases ensures minimal air exchange between internal display space and external atmosphere to be not more than 0.1 times per 24 hours.
Air exchange rate (AER) can be tested by standard tracer gas measurement.For this purpose, a small amount of the tracer gas is released in display space and its concentration is then recorded as a function of time. Subsequently, using evaluation algorithms the AER can be calculated from the data obtained.The first section is introducing basic physical principles of air change processes between internal display space and external atmosphere,followed by a description of tracer gases which are frequently used in daily routine, and methods determining the AER. Moreover, the applicability of carbon dioxide as a tracer gas has been compared with results obtained by hexafluorobenzene or sulphur-hexafluoride.