These pages and the IMPACT pollution model they support are intended to help conservators, conservation scientists and other professionals in musuems, galleries, historic houses, libraries and archives deal with the issue of pollution damage to collections.

They assume that the reader has some background knowledge about air pollution; a list of references giving the background to the subject is included in the bibiography.

How to assess the pollution threat to a collection

In order to make an assessment it is necessary to consider:

1. The object or materials and their susceptibility to pollution damage
   
   
2. The overall pollutant dose (i.e. pollutant concentration x time of exposure) that objects have received in their past history, or are projected to receive in the future. Other factors being equal, pollutant damage to an object is proportional to the pollutant dose it has received.
   
   
3. Pollutant concentration. The concentration of damaging pollutant in the air will give a measure of the rate at which pollutant damage is likely to occur, but not the ultimate degree of damage, or usable lifetime of an object, which is dependent on the dose.

On (1), there is a considerable amount know qualitatively about the interactions of objects and air pollutants. Rather less is know about what is an acceptable pollutant dose or concentration, and although standards do exist they are rarely based on the scientific understanding of air pollution damage, but rather on what can be practically achieved, or seems reasonable from empirical evidence. Blades et al (2000) and Brimblecombe (1990) provide good starting points for further exploration of the subject.

The concept of dose (2) is increasingly being seen as key to the understanding of pollution damage to materials. Tetreault (2003) and Brimblecombe have written extensively about this topic.

The IMPACT software was developed in the EC FP5 Project ‘Innovative Modelling of Museum Pollution and Conservation Thresholds’, 2000-2004, Contract No. EVK4-CT-2000-00031.

This project was led by the UCL Centre for Sustainable Heritage in partnership with the Norwegian Institute for Air Research, School of Environmental Sciences, University of East Anglia, National Museum of Krakow, Emcel Filters Ltd and Architecture Project, Malta.

The contribution the IMPACT tool can make

The IMPACT model can estimate the indoor/outdoor ratio of damaging external air pollutants in buildings, and hence the indoor concentration (3), if the outdoor concentration is known. Outdoor pollution concentration data are available from local and national monitoring networks, such as The Europe-wide EMEP project and EuroAirNet and for the UK, the National Air Quality Information Archive. For most locations in Europe it should be possible to obtain an estimate of the outdoor pollutant concentration from these types of source.

As well as providing an estimate of the indoor pollutant concentration that objects are exposed to, the IMPACT software can help understand how well a particular building controls air pollution, and how it could be improved. Both naturally ventilated and mechanically ventilated buildings can be studied.

The IMPACT model will also give an indication of the interior surfaces on which pollutants are reacting - which materials are reactive, which are inert. These will include the surfaces of the objects themselves as well are the building interior finishes.

Selected Publications on IMPACT

Blades, N. and Kruppa, D. and Cassar, M. (2002) Development of a web-based software tool for predicting the occurrence and effect of air pollutants inside museum buildings. In: ICOM Committee for Conservation, 13th Triennial Meeting, Rio de Janeiro, 22-27 September 2002. Maney Publishing, London, UK, pp. 9-14. ISBN 9781902916309.

Blades, N. (2007) Application of an air pollution modelling tool to cultural heritage buildings. In: Proceedings of the 7th EC Conference 'Sauveur' Safeguarded Cultural Heritage Underdstanding & Viability for the Enlarged Europe. Institute of Theoretical and Applied Mechanics of the Academy of Sciences of the Czech Republic / European Communities, Prague, Czech Republic, pp. 363-376.

Grzywacz, C. (2006) Monitoring for Gaseous Pollutants in Museum Environments. The Getty Conservation Institute, Los Angeles.

Grontøft, T. and Raychaudhuri, M. (2004) Compilation of tables of surface deposition velocities for O₃, NO₂, and SO₂ to a range of indoor surfaces. Atmospheric Environment 38 (4) 533-544.

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