BS EN 15757:2010 pdf free download Conservation of Cultural Property — Specifications for temperature and relative humidity to limit climate- induced mechanical damage in organic hygroscopic materials
This European Standard is a guide specifying temperature and relative humidity levels to limit climate-inducedphysical damage of hygroscopic,organic materials, kept in long-term storage or exhibition (more than one peryear) in indoor environments of museums, galleries, storage areas, archives, libraries,churches and modernor historical buildings.
Normative references
The following referenced documents are indispensable for the application of this document. For datedreferences,only the edition cited applies. For undated references,the latest edition of the referenceddocument (including any amendments) applies.
prEN 15898:2010,Conservation of cultural property — Main general terms and definitions concerningconservation of cultural property
3Terms and definitions
For the purposes of this document, the terms and definitions given in prEN 15898:2010 and the followingapply.
3.1
active control
use of devices able to force exchanges of heat, moisture or air,integrated with real-time processing sensorsand controllers
3.2
air temperature
temperature read on a thermometer which is exposed to air in a position sheltered from direct solar radiationor other energy sources
NOTE lf objects are exposed to direct radiation black globe or black strip thermometers should be used. Fordefinition see also EN 15758.
3.3
equilibrium moisture contentEMC
moisture content at which a hygroscopic material neither loses nor gains moisture from the surroundingatmosphere at given relative humidity and temperature levels
3.4
Heating, Ventilating or Air Conditioning SystemsHVAC
active systems operated to control air temperature (heating), air temperature and humidity (air conditioning),or ventilation in a building
3.5
historical climate
climatic conditions in a microenvironment where a cultural heritage object has always been kept, or has beenkept for a long period of time (at least one year) and to which it has become acclimatized
3.6
hygroscopic material
material which adsorbs moisture when the environmental relative humidity rises, and loses moisture when relative humidity drops
3.7
indoor environment
area within a building where cultural heritage objects are preserved
3.8
microclimate
climate on a small spatial scale
NOTE Typically refers to the microenvironment that interacts with the objects under consideration.
3.9
Relative Humidity
RH
ratio of the actual water vapour pressure to the saturation vapour pressure
3.10
target level
RH level that should be maintained to best ensure preservation
NOTE Determined by the historical climate of a given environment that has been proved not to be harmful to the preservation of objects. Otherwise, it should be specified by a qualified conservation professional.
3.11
target range
range of RH fluctuations that should be not be exceeded to best ensure preservation
NOTE Determined by the historical climate of a given environment that has been proved not to be harmful to the preservation of objects. Otherwise, it should be specified by a qualified conservation professional.
4 General recommendations for organic hygroscopic materials In general, organic hygroscopic materials require a mid RH range as the extremes (high and low RH ranges), affecting the EMC, can result in structural damage, deformation and cracking. However, a material that has been stored for significant periods of time even in a poor quality environment will have become acclimatised to the conditions. Careful analysis of the material‟s needs is required to ensure that specified standard levels do not generate further damage. Any change from a particular historical climatic environment may be problematic, even though the new conditions appear better for long-term preservation. If the change is sudden, the strain-stress may generate a climatic „shock‟ leading to more intense levels of damage. Even if the change is slow, it may still generate stress and result in damage. Therefore, the strategy of this standard focuses on maintaining the microclimate in terms of levels, seasonal cycles and fluctuations of temperature and RH, to which the materials have become acclimatized for a long time if this microclimate has been proved not to be harmful. Before a decision is made on the harmfulness or otherwise of pre-existing climatic conditions, the professional conservator involved in the project should carry out a condition report on the most vulnerable and/or valuable objects to be subjected to any environmental control proposal.