Avoiding Collections Damage from Pollutants
Exposure to some volatile organic compounds (VOCs) can accelerate oxidation and hydrolysis in collection materials, evidenced by discoloration and other degradation. VOCs can come from external sources, such as outside (make-up) air, and internal sources, such as copying equipment and materials used in buildings, exhibit cases, frames or furniture, including paint, wood, plastics, or fabrics. Sometimes VOCs are emitted by collections themselves.
Wherever possible, exposure of collections to VOCs should be limited. Best practices dictate that only the most stable materials be used in proximity to collections. This means limiting VOCs known to damage collections to the levels listed below:
Table 1: Maximum Permitted Air Pollution after Filtration (in parts per billion)1
Sulfur dioxide: 1.0 ppb
Nitrogen dioxide: 2.6 ppb
Ozone: 4.0 ppb
Formaldehyde: 4.0 ppb
Acetic acid: 4.0 ppb
Table 2: Unstable Housing, Case, and Construction Materials2
acid-curing silicones, sealants, and adhesives
Materials containing asbestos, sulfur or lead
Vinyls, including, but not limited to, unstable chlorine-containing polymers (e.g. polyvinyl chloride (PVC), vinylidene chloride)
Polyurethane-based products, including, but not limited to, paints, varnishes, and foams
Pressure-sensitive adhesives that release VOCs
Materials containing cellulose nitrate (e.g. lacquers and adhesives)
Fabrics and films containing cellulose acetate
Oil-based paints or varnishes
Modified alkyd paints
Any material that emits formaldehyde (urea, phenol, resorcinol, formaldehyde), including, but not limited to, plywood, particle board, hardboard, and plastic laminates
1 Values from NARA 1571, Archival Storage Standards, February 15, 2002. http://www.archives.gov/foia/directives/nara1571.pdf, [PDF 94.6 K / 16 p.] accessed 1/30/09. For a helpful summary of prohibited materials, good practice for collections environments at every scale, and environmental storage standards, see this document from the National Archives and Records Administration.
2Content from von Endt, D., Erhardt, W.D., and Hopwood, W.R. 1995. Evaluating Materials Used for Constructing Storage Cases. In: Storage of Natural History Collections: A Preventive Conservation Approach, editors, C.L. Rose, C.A. Hawks, and H.H. Genoways, 269-282. Pittsburgh, PA: Society for the Preservation of Natural History Collections.