Detection and mitigation of museum pollutants: An update

Cecily M. Grzywacz

Abstract

The conservation community has been aware of the effects of the environment on cultural property for the last several years. This recognition was precipitated by the number of reported incidents of object damage while on display or storage. Based on these concerns, research has developed in the areas of environmental testing, evaluation of building materials and pollutant mitigation. This presentation will discuss current research in these areas. In the 1980s, The Getty Conservation Institute (GCI) developed a research program targeting indoor-generated carbonyl pollutants found in museum environments. The goal of this research program was to provide an integrated problem solving approach to the study of carbonyl pollutants in museum environments. From this research base, other related programs were developed, including analysis of volatile organic compounds released from display and storage case materials and physical and chemical mitigation of pollutants.

Carbonyl pollutants, such as formaldehyde and acetic acid, have been suspected to cause damage to objects on display or in storage. Whether or not all collections regardless of building type or collection type had high levels of these pollutants was investigated. The GCI sampled indoor environment at 16 collecting institutions from four general areas or site types: galleries, storage areas, storage cabinets and display cases. The survey demonstrated that problem areas were specific to building materials used and air circulation patterns. While concentrations of carbonyl and carboxylic acid pollutants measured during the air survey ranged from less than the analytical detection limits, 0.2-0.5 parts per billion (ppb), to over 1500 ppb, the majority of the sites surveyed had concentrations of each pollutant less than 20 ppb. Less than 15% had concentrations of pollutants higher than 100 ppb. Concentrations of carbonyl and carboxylic acid pollutants, in general, increased in the following order of the sampling site type: galleries < storage areas < display cases and storage cabinets This order reflects the difference in air circulation and air exchange between galleries and display cases.

An advanced technical survey of carbonyl concentrations is not necessarily accessible to all institutions. For this reason, economical passive sampling devices were identified that would provide reliable pollutant concentration data. The GCI evaluated a number of commercially available passive monitors and identified the Series 570 Formaldehyde Badge (GMD SYstems, Inc.) for detection of low levels of formaldehyde. A direct reading (no analysis required) passive dosimeter was also evaluated. still the question remained, “where do these pollutants originate?” To determine the source of pollutants, a systematic study of volatile organic compounds (VOCs) emitted from materials used in the construction of display and storage cases was conducted. A list of the most frequently used materials for display, storage and transportation of objects was compiled from a survey of over 1600 preparators and objects conservators. Based on this list, the testing of materials began. The VOCs were determined by gas chromatography-mass spectrometry (GC-MS). The type and concentrations of VOCs from various materials were determined with this highly sophisticated technique.

The problem of airborne carbonyl pollutants in the museum environment can rarely be completely eliminated; hence economical mitigation techniques are frequently sought. Barriers between the source of pollutants and the objects may be installed. These may be physical, as in the lining of a case with aluminum-barrier foil, or they may be chemical, ie., coating the source.

In light of the fact that museums continue to use wood products as construction materials and that some of these products have been associated with significant damage to museum collections, conservators have recommended the coating of wood products in an effort to mitigate the emission of volatile acids and aldehydes. The Museum of Fine Arts (MFA) in Boston has attempted to identify coating materials that would minimize the release of volatile organic compounds in enclosed environments and safely provide some degree of vapor barrier. Two products, Sancure 878 ( Sanncor Industries) and Polyglaze 1-146 (Camger Chemical Co.) were evaluated by the MFA and found to be acceptable barriers for construction products.

Another approach to mitigation, rather than isolate the source of the pollutant from the object, is to purify the micro-environment by scavenging pollutants with sorbents. Activated charcoal or potassium permanganate can be used to scavenge harmful pollutants. The results of a study on the effectiveness of various sorbents in display cases will be discussed.

Another alternative is active mitigation. To this end, the GCI focused its research on the development and testing of an active recirculation pollution-elimination unit which can be run in enclosed spaces to decrease measured concentrations of pollutants in problem storage cabinets or display cases.