Current Thinking on Environmental Standards

Introduction

When it comes to standards for environmental conditions in museums, libraries and archives, current thinking does not appear to be greatly different to past thinking. All of the relevant information has been around for decades. Recent work has refined understanding rather than revolutionising it. All of the possible attitudes to this information have been published at various times during the thirty-something years that I have had an interest in the subject. The thing that does change with time is fashion. What changes is the selection of information and the emphasis on a particular attitude. This specific emphasis can be the deliberate choice of the author, or result from unconscious filtering in the mind of the reader.

The reason it is possible to have changes in fashion, without any substantive change in the context or the relevant data, is that standards present a fundamental dichotomy. There are two distinct groups of people. People like you who need standards because you need to be told exactly what to do and how to do it. Then there are people like me, who are intelligent and sensitive. We can work things out for ourselves and don't need to be tied down by petty regulations that stand in the way of progress. The pendulum appears to swing, sometimes favouring liberalisation, sometimes favouring control. But any sense of a long-term trend is illusory.

A paradigm shift?

For the most recent published thinking in the conservation arena we can go to the pre-prints of the 14th Triennial meeting of ICOM-CC in The Hague in September 2005. In the oral presentation of their paper, authors Rob Waller and Stefan Michalski [1] claimed that attitudes to preventive conservation are undergoing a paradigm shift. Preventive conservation is in danger of becoming nothing more than the mindless adherence to ritualistic procedures. The proposed saviour of the situation is ‘predictive conservation'.

Applying this new attitude to environmental parameters, we can move on from defining the tightly specified rectangle of conditions (eg 20 ±1??qC, 50 ± 5% RH) as the only allowable place to be, or to strive to be. We can now take time to look at the environmental conditions we have at the moment, and then predict what the consequences for our collections will be in the long term. We may feel able to accept the outcome. But if we are not happy, we can choose another environment that gives a more acceptable predicted outcome. We then work out whether we can afford the cost to our purses, and to the collection, of making the transition.

This system replaces mindless procedure with intelligent procedure, but is not an attack on standards. It's another type of standard.

Types of standard

During the late 1960s my parents and my colleagues considered me to be some kind of hippie. On several occasions I was refused service in pubs because of my long hair or because I was not wearing shoes and socks. The reason given was always that “we have to preserve standards”. This is the Type 1 standard that says “we want you to be like people like us.”

This was not a universal standard and I could always find a pub where I would be served. In these places I became the setter of standards. I needed to know that when I asked for a pint of beer I would be served exactly one English pint of beer with a specified alcohol content. I would have none of this glass half-full of foam that they seem to allow in foreign parts. This is the Type 2 standard that says “I want to know that what I ask for is what I get.”

Type 1 standards are the basis of benchmarking. Forms of observed or possible behaviour are classified and ranked. People in the lower ranks are encouraged to upgrade.

Type 2 standards facilitate trade and communication. They do this by trying to ensure that words and numbers relating to different activities can unambiguously be understood and acted on by different groups. So that when I use one tape measure to assess my waist size, someone in the Philippines can use another tape measure to gauge how much denim to cut. When I go to a shop and ask for my size in jeans, I get a pair that fits.

Type 2 standards are useful for people who want reusable specifications. They can however become the currency of mindless regulation.

In theory standards do not impose the will of the few on the many. Everyone is supposed to feel the benefit. BSI, the British Standards Institute, defines
standardization as: “Establishing and applying an agreed set of solutions, intended for repeated application, directed at benefits for stakeholders and balancing their diverse interests.”In theory standards need consensus before they can be applied. ISO, the International Organization for Standardization, defines a standard as:

“A document established by consensus, and approved by a recognized body, that provides for common and repeated use, guidelines or characteristics for activities or their results aimed at the achievement of the optimum degree of order in a given context.” [2]

There needs to be a document, something that anyone can read. Its content must be the result of agreement between relevant professionals. The bit about a “recognized body” is probably where some environmental standards come unstuck for conservators. No international, or large national,
conservation body has ever prepared or endorsed any relevant standards, even though a number of such institutions claim that one of their priority interests is ‘standards'.

Even if you believe that standards come from consensus and represent agreement, you still have a dilemma. Does agreement signal the start of uncontested regulation, or is it merely an agreed starting point for continuing discussion?

Fashions in standards

Below are seven pairs of words, each word is related to an attitude to what a standard should contain and how it might be implemented.

A standard can be universally applicable, or it might reflect that there are local differences that must be accommodated, such as geography and climate. It might give general guidance on a range of object types, or relate to just one specific type, such as archives or photographs. The wording of the standard may imply a degree of coercion to comply, or it may suggest
guidance that can be ignored or modified in some circumstances.

The basis for the standard may be the best performance of the best available technology, or the basis may be the needs of the collection, modified by the limitations of the building. Some standards appear evangelical, yet others may accept that not everyone can afford redemption. The certainty that non-standard conditions will cause damage may appeal to some people more than the risk concept that suggests that only probabilities can be predicted, and then only with some uncertainty. Fixed numbers can be useful for setting controls but, given the complexity of the interactions between collections and environment, an indication of general direction for the environment might be safer.

All of these different approaches have been expressed at various times in discussions about the control of the museum environment. It is tempting to see the left-hand column as descriptive of the bad old days and the right-hand column expressing the new and enlightened era. However there have been ineffectual discussions about risk and cost-benefit for at least ten years, while further fixed numbers were published less than three years ago.

If you are looking for fixed numbers you will not find them in the publications of authorities such as MLA, the Museums Libraries and Archives Council, or its previous incarnation Re:source. Publications such as “Benchmarks in Collections Care” [3] and the MLA “Accreditation Standard” [4] imply that environmental control is important, but stop well short of suggesting even loose or flexible specifications. This might be considered a good indication of the enlightened trend in standards.

The primary purpose of these documents is to promote and assess levels of institutional competence. It is not their role to give reasoned guidance. Instead they offer set procedures, and procedures for showing that procedures are being followed.

The Environment

The factors that most people would want to see included in an environmental standard are pests, particulates, pollution, light, temperature and humidity. As a first step towards defining appropriate standards, these can be divided into three groups. Different types of standard may be needed for the different groups.

For the first three, zero is a reasonable target. No-one would object if you said that your ambition was to eradicate pests, dust and pollutants. Total eradication may not be possible, but the ideal is not stupid. In the case of light, zero ultra-violet content may be reasonable, and zero light when there is no-one to see the objects may be reasonable. But if someone wants to see the objects there must be light. Standards must reflect the needs of the viewer and the vulnerability of the collection.

The principle damage caused by light is due to chemical change. Humidity and temperature are implicated in both physical and chemical change. You cannot remove temperature from the environment. All you can do is define temperatures that are too high or too low for the physical well-being of the object and the comfort of the visitor. As far as chemical reaction is concerned, absolute zero might seem an ideal target, but unlike a target of zero bugs or zero dust, the cost and consequences of heading in that direction make it unfeasible.

For the majority of objects where levels of humidity are a concern, water molecules form an integral part of the structure of the object.

To head for zero humidity would be to radically change, if not destroy, the object. Standards must indicate levels that keep chemical reactions slow, while maintaining the physical integrity of the object.

Pests

Standards for pests in museums do not discuss permissible levels of population in the way that allowable levels of pollutants might be proposed. Nor do standards for pests suggest that a certain level of damage is unavoidable and so must be acceptable, as has happened with lighting guidelines.

The regulation of chemical means to reduce pest populations means that is more difficult to aim for zero tolerance. The guidelines that are available to museums concentrate on procedures to improve monitoring and to ensure hygiene. [5]

Particulates

What are sometimes taken as standards for levels of particulates are specifications for the efficiency of the filters within air handling equipment. Although frequently requested by conservators, specifications such as Eurovent 4/5 do not directly relate to the particle concentrations and size
distributions you might expect in a gallery.

At best such a specification gives assurance that, if it were tested in a properly equipped laboratory, this filter would stop a certain percentage of particles of a certain size. The standard takes no account of the real-life installation, or of levels of maintenance and replacement, or of activities within the gallery space. And of course it can only be applied when there is mechanical air-handling.

The increased level of building works in museums in the last few years of the 20th century, resulting from millennium fervour and funding, brought a renewed interest in dust. Particulates can be considered in two classes: those that are very small and so stay in the air for a long time, and those that are larger and tend to fall and cause visible dust coverings on the horizontal
surfaces of objects. In the UK, conservation science has largely ignored the first group. Concentrations of the second group can be measured using a fairly cheap low-tech method, the change in gloss of a microscope slide. [6]

Current thinking about dust levels comes from the results of widespread fashion for this method. Although not uncontested as an appropriate unit of measurement, a number of papers propose measuring dust concentrations in terms of soiling units. Building work causes high levels greater than 30 soiling units a week, general human activity causes levels below 10 soiling units a week [7]. A standard might be set by declaring what level of activity is tolerable, and so what soiling level is acceptable. A different approach has been to compare the rate of soiling with the economic demands of cleaning and maintenance and the probable damage caused by these activities. [8]

Pollutants

For a long time the major concern was about levels of pollutants brought in from the outside. Standards for levels of sulphur dioxide, ozone and nitrogen oxides were determined by the best that air-conditioning with activated carbon filters could achieve. More recent thinking has been concerned with levels of internally generated pollutants such as formic and acetic acids emitted by timber products and adhesives. Much of current thinking has been published by Jean Tétreault from the Canadian Conservation Institute [9]. His is a risk-based approach where the allowable levels of pollutants are determined by the decision on how long you want your collections to last. He
proposes a dose relationship allowing you to juggle concentration and time of exposure, in a manner that has become familiar with intensity and time of exposure for light dose. He also talks about the NOAEL, the No Observable Adverse Effects Level, a concentration of pollutant in the environment below which no damage appears to occur. The idea that such a level exists is seductive and is supported by anecdotal evidence. However it is not
supported by critics of Tétreault's experimental technique [10].

Light

The conservation department at the V&A is responsible for the most recent practical thinking about allowable lighting levels, [11] although these ‘new' developments are based on earlier, less accessible, work from the Canadian Conservation Institute. The V&A approach is essentially risk-based, not surprising given my involvement. It relies on determining what a perceptible change (PC) in colour is, and then asking what rate of change is acceptable. The conclusion that one PC in 50 years is acceptable will not greatly alter the way light-sensitive objects are treated in a well-run museum. It does however openly recognise that the viewer has both limitations and rights, and that the custodian must accept that the decision to display is a conscious decision to damage.

Temperature and Relative Humidity

To find out the latest thinking on standards for RH and T you could try going to the Environmental Monitoring and Control section of Conservation on-line [12]. What you will find is a number of animated essays, most of which date from 1995-96. The cause of this flurry of animation was a press release from the Smithsonian Institute in 1994. It stated that research at the Smithsonian had shown that the current allowable range for relative humidity, of
± 5% (or less), was unnecessarily rigid. Moreover the trend towards tighter
specification would lead to unnecessary expenditure on fitting and maintaining air-conditioning plant. Since this was a charter to avoid unnecessary worry it was not popular with conservators. The fact that it was couched in economic terms, rather than valiant defence of the collections, was even more annoying.

What the Smithsonian scientists had shown was that for a large number of samples the internal stress that was large enough to take the internal strain beyond the elastic limit was not reached with fluctuations much larger than the accepted specification [13]. Although Stefan Michalski chose to
criticise the experiments that supported these results, he had published similar conclusions at around the same time [14].

The Smithsonian work dealt with the physical effects of temperature and humidity. At around the same time the standards relating to the effect of temperature and humidity on chemical degradation were also being questioned. At a conference on photographic conservation held in Copenhagen in 1995, Tim Padfield and Jesper Stub Johnsen demonstrated the limitations of the existing standards for photographic archives [15]. They maintained that “ Standards have an authority that encourages acquiescence without deeper consideration, particularly by administrators who have little knowledge of the experimental or experiential basis for the standard.” One point made in their paper was that for the climate of Copenhagen a
flattish line for RH, at levels well within accepted guidelines, can be achieved simply by raising the temperature. Unfortunately this increases the rate of degradation by a factor of at least two, and so they propose dehumidification as a better solution. This was shortly after the National Trust had won a Conservation Award for the concept of ‘conservation heating' where the air inside historic houses is heated to 5 degrees above the outside temperature. This prevents humidities from staying too long in the mould region, but has consequences for the preservation of the collections which are at odds with stated aim of conservation. It should however be noted that conservation heating does give lower degradation rates, and saves more energy, than heating to the 19 or 20 degrees centigrade required by other ‘conservation' standards.

ASHRAE

In North America the bible for environmental standards is the ASHRAE Heating Ventilation and Air-conditioning Applications Handbook, [16] which has a chapter on Museums, Libraries and Archives. ASHRAE is the American Society of Heating Refrigerating and Air-conditioning Engineers. Its mission is “advancing HVAC&R to serve humanity and promote a sustainable world”. So its aim is to promote the installation of energy-consuming equipment while stopping global warming? The proposed specifications do not save the planet, sustainability is not yet one of the criteria for museum environment standards, but ASHRAE is right to draw the problem to our attention.

The Handbook is a set of specifications for use by engineers. Conservators seem to like it because it is written with engineers in mind, so it makes the difficult task of communication with engineers more easy. As a set of specifications for use by engineers it works quite well, but as a set of standards it lacks something because it starts with the presumption of active mechanical control. The other reason conservators like the “ASHRAE chapter”, as it is called, is because the lead writer for the 1999 and 2003
editions is Stefan Michalski. Most people have some respect for what he says, which almost makes what he says the consensus view.

The Handbook specifies five types of environment, starting with one where the only constraint is that is ‘reliably below 75% RH', and moving up to a tight specification of precision control, with no seasonal variation, of ±5% RH and ± 4??qF (this is America!). Intermediate specifications allow for some difference in set point between summer and winter. Each set of conditions is accompanied by a description of the risk to the collection. It is interesting to note that the tightest specification, which leads to “no risk of mechanical damage”, is ±5% and not the previously fashionable ±3% or the totally ludicrous ±1% once called for by the Royal Collection.

You could think of the five sets of conditions, not as specifications for equipment, but as descriptions of types of building with different possibilities for control. Such a classification has recently been developed within the MASTER EU research project [17]. This work, recently presented at the final workshop for the project in January, has yet to be published.

BS 5454

To return to the ICOM-CC conference in the Hague and to the idea of prevention of chemical degradation as the focus of a standard, let us consider some more work from the V&A [18] We have to refer to the most referred-to standard in the UK, BS 5454, ‘Recommendations for storage and exhibition of archival documents', updated in 2000. In the foreword to the document it is stated that this standard “takes the form of guidance and recommendations. It should not be quoted as if it were a specification...”. However providers of grants for building work such as the Heritage Lottery Fund often stipulate compliance with BS 5454 as a condition of the grant. Unfortunately it is difficult to comply with the standard without installing air-conditioning plant. Apart from the criticism of its global-environmental unsustainability, air-conditioning also takes up space, abuses historic architecture and costs a lot to keep it running. Yet the HLF insists, and MLA uses the standard as the definition of ‘best practice' in its benchmarking scheme.

In his paper Boris Pretzel describes the environmental needs of the RIBA Archive, the collection whose housing the HLF was being asked to fund. He argues that, for individual sheets of paper, environmentally induced stresses are not a major problem, and that at the perennially dry V&A neither is mould. This leaves chemical degradation caused by oxidation and hydrolysis as the major factor to be controlled. Permanence is the key issue.

The concept of the isoperm, originated by Donald Sebera in the 1980s, has recently been given new life by Stefan Michalski [19]. If a graph is created with temperature and humidity as its two axes, lines can be drawn which join points of identical rates of degradation. Isoperms are lines which join points of equal permanence, which is another way of saying the same thing. Where temperature and humidity are high, in the top right corner of the graph, the rate of degradation will be high. Where temperature and humidity are low, down in the bottom left, the rate of degradation will be low, that is the permanence will be much greater. BS5454 allows a small rectangle of values for RH and T. Every possible point to the left of an isoperm that passes through the BS5454 permitted space will have as great or greater permanence than that specified. Yet nearly all of these better sets of conditions fall outside the standard! Boris argues ad absurdum that conditions in an outdoor location, exposed to external conditions but sheltered from rain and direct sunlight, give a greater permanence than BS 5454.

CEN

CEN – the European Committee for Standardization [20] is the sort of
organisation that will standardize anything that moves, or that sits still for too long. In response to an Italian initiative it has set up a Technical Committee, TC346, to look at all aspects of conservation work. One Working Group, CEN TC 346 WG4, convenor Jesper Stub Johnsen, is looking at Environment. This is work in progress and I have been unable to find out the direction the working group is taking.

In a promotional presentation that can be down-loaded from the web, CEN describes the justification of standardization: “harmonization diminishes trade barriers, promotes safety, allows interoperability of products, systems and services, and promotes common technical understanding.” Which is reasonable enough.

The presentation also contains the line that CEN's objectives “may be attained by all means”, which gives a hint of Europe 1939 rather than liberal 21st century explanatory guidelines. I predict more fixed and inflexible numbers.

References

1. ‘A paradigm shift for preventive conservation, and a software tool to facilitate the transition'. Robert Waller and Stefan Michalski. 2005. ICOM-CC. Preprints of the 14th triennial meeting, The Hague. ISBN 1-84407-253-3 pp 733-738.

2.‘Exploiting Research through Standardization: a best practice guide'.
Maxiquest-norm, 2003. http://www.maxiquest.net

3. ‘Benchmarks in Collection Care'. re:source (now MLA). 2002.

4. ‘Accreditation Standard'. MLA, 2004
http://www.mla.gov.uk/resources/assets/A/ accreditation_standard_pdf_6686.pdf

5.‘Integrated Pest Management: a guide for museums, libraries and archives'.
David Pinnegar and Peter Winsor. MLA. ISBN: 1-903743-79-6
http://www.mla.gov.uk/resources/assets//I/ipm_guide_pdf_6640.pdf

6.‘Dust deposition and measurement-a modified approach'. Stuart Adams.1997.
Environmental Technology, 18, pp 345-50.

7. eg ‘Monitoring of deposited particle levels within the Royal Museum of Scotland'. Stuart Adams, Katherine Eremin and James Tate. Conservation Science 2002, Archetype Publications.
And follow arguments at http://iaq.dk/iap.htm

8. ‘Economics of dust'. Helen Lloyd. 2004. 6th European Commission Conference on Sustaining Europe's Cultural Heritage: from Research to Policy, London, 1-3 September 2004.
http://www.ucl.ac.uk/sustainableheritage/conference-proceedings/pdf/3C.8_lloyd.pdf

9. ‘Airborne pollutants in museums, galleries and archives: risk assessment, control strategies, and preservation management'. Jean Tétreault. 2003. Canadian Conservation Institute. ISBN 0-662-34059-0

10. ‘The relevance of the NOAEL concept and related parameters in defining pollution thresholds for cultural heritage collections'. Jens Glastrup. 2004.
http://www.isac.cnr.it/iaq2004/pdfabstract/glastrup_abstract.pdf

11. ‘The continuing development of a practical lighting policy for works of art on paper and other object types at the Victoria and Albert Museum'.
Jonathan Ashley-Smith, Alan Derbyshire and Boris Pretzel. 2002, ICOM-CC, Preprints of the 13th Triennial Meeting Rio de Janeiro. ISBN1-902916-30-1. pp 3-8.

12. http://palimpsest.stanford.edu/bytopic/environment/

13. eg. ‘Technical considerations for the transport of panel paintings'. M. Richards, M.F. Mecklenburg and C.S. Tumosa. 1998. The Structural Conservation of Panel Paintings.
Proceedings of a symposium at the J Paul Getty Museum, April 1995.
(ed. Kathleen Dardes and Andrea Rothe) J Paul Getty Trust.
ISBN 0-89236-384-3

14. ‘Relative Humidity and Temperature Guidelines: What's Happening?'
Stefan Michalski, 1994.CCI Newsletter No.14 September 1994.
ISSN 1180-3223. pp. 6-8.

15. ‘The breath of Arrhenius: air-conditioning in photographic archives'.
Tim Padfield and Jesper Stub Johnsen. Research Techniques in Photographic Conservation. Proceedings of the conference in Copenhagen 14-19 May 1995. pp 59-64.

16. ASHRAE HVAC Applications Handbook 2003. ISBN 1-931862-22-2

17. http://iaq.dk/iap/iaq2003/posters/master.pdf
http://www.ucl.ac.uk/sustainableheritage/research/masterfinalworkshop.html

18 ‘The RIBA project: a climate strategy for paper-based archives at the Victoria and Albert Museum'. Boris Pretzel. 2005. ICOM-CC. Preprints of the 14th triennial meeting, The Hague. ISBN 1-84407-253-3. pp 681-688

19 ‘Double the life for each five-degree drop, more than double the life for each halving of relative humidity'. Stefan Michalski. 2002. ICOM-CC Preprints of the 13th Triennial Meeting, Rio de Janeiro.
ISBN 1-902916-30-1. pp 66-72

20. http://www.cenorm.be/cenorm/index.htm