Introducing the Agents of Deterioration

by | Jan 12, 2023 | Blog

The agents of deterioration (AoD) is a tool developed by the Canadian Conservation Institute (CCI). Inspired by risk management, the AoD can provide those responsible for collection care with a checklist of things that can cause loss to their collections.

Agents of deterioration and risk frameworks

The 10 agents of deterioration sit within a very useful management framework also developed by CCI. In the ABC method, we are encouraged to consider the layers around our assets from the immediate packaging, considering the fixtures and the building right up to the location. 

A textile might be fading because it is displayed next to a window, because there is a display lamp pointing at it or because the filming and photography protocols don’t manage the length of exposure.

If you work with the AoD you will work on the source, the path and the effect (Waller 2013), and calculate the significance of the risk and plan the solutions from there.  

The AoD are specific to collection care or conservation related risks.

There are many other risk frameworks to consider other risks such as technical obsolescence, political change, or the growing climate crisis.

You can see a guide to SWOT and PESTLE analysis for smaller museums produced by the Cornwall Museum Partnership. 

By the way, you might be interested to know that some professionals including Rob Waller call the AoD ‘agents of change’ because the change is what happens when exposed to the agent, but it is only deterioration if it is considered to be a loss of value.  

Meet the agents of deterioration

Physical forces appear first in the 10 agents and this agent is probably responsible for the most loss in heritage collections. 

Physical forces can be sudden, such as dropping an object, or ongoing such as vibrations in a lorry in transit. They can result in an object breaking after a sudden impact or in a painted surface becoming dislodged due to vibrations.

Many of the responses to physical forces will be procedures (such as handling training) but you might also use fixtures and fittings such as safe picture hanging or adapting the building.

Many of the agents are self-evident. Thieves and vandals damage collections regardless of whether they are visitors or staff, and regardless of their motivation.  

An emergency response plan will be an important document for the management of theft as well as fire and water which often arrive together if there is a fire. Water may also arrive as a result of flooded guttering, a leaking tap or an over enthusiastic cleaning program. 

Most heritage organisations are aware of the need for an integrated pest management (IPM) strategy which will be another tool in the collection management armoury.  

All the following four agents:  Pollutants, Light UV and IR, incorrect temperature, and incorrect relative humidity are those we most associate with advice on the museum environment.

They are impossible to avoid and so we aim to manage them to reduce unnecessary damage.

We will always have these agents present but we will plan to have generally safe conditions, establishing targets for most of the collection and putting special measures in place for our most vulnerable objects.  

Pollution, UV and IR targets are normally as low as possible, and temperature and humidity set for the location and collection type. When we consider visible light levels, the targets come from user needs. Objects rarely need to be lit except when people are looking at them – so set levels for the needs of your users. 

Perhaps the least understood AoD is dissociation.

The CCI mainly describes this in terms of the loss of information in the sense of disconnecting an object from its documentation. Other people, including me, use it as a more general term for loss of information, perhaps failing to capture the wishes of a donor community or separating a working thing to components until its value is obscured.


The AoD are all around us and they interact with each other. Insect pests will be more problematic in warm and damp conditions, physical damage is more likely when handling paper if it is wet, and corrosion will be affected by pollutants, temperature and humidity. Improvements in one area of your work can lead to multiple benefits and is an important feature to consider when devising a Collection Management Plan.

Agents of deterioration and environmental monitoring

Detect is the third level of the management strategy Avoid – Block – Detect so it is an evidently critical aspect of managing the AoD. 

The best way to collect data is to have an idea of what you want to know and ideally also what you want to achieve.

That means you will have good reason to check-in frequently with your collected data and have a trigger for when to act. Write a list of what you want to know from your data collection devices and then place them where they answer your questions.

Most people monitor conditions right where their collections are – on the shelf or in a case – but you might have other questions. Do you want to know if an empty room might be a good collection space, or should you be setting pest monitors near your chimney to find out if pests are getting in through it?

Don’t be tempted to collect data you won’t use, and if you collect data, make sure you do something with it – after all your time is precious. 

Monitoring is just numbers until you make changes so commit a proportionate amount of time for interpretation and action. A monthly check in and an annual review and report is probably the minimum I would recommend. It would be more if you are tracking an active insect infestation or in dispute with your HVAC supplier, but if you are lucky enough to have uneventful and generally stable conditions, you should at least reassure yourself from time to time that nothing has changed.

Be a conservation detective

The agents of deterioration is a super handy and internationally recognised checklist of issues to help you think systematically about how to protect your collections. Be a conservation detective and make sure you plan and maintain your collection management to empower you to make great decisions for your collections.

Hear more from Jane Henderson, Professor of Conservation at Cardiff University, in the Conserv Community.

If you have any questions about environmental monitoring, integrated pest management, or just want to talk about preventative conservation, please reach out to us! Don’t forget to check out our blog or join our community of collections care professionals where you can discuss hot topics, connect with other conservators or even take a course to get familiar with the Conserv platform.

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