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Monitoring Humidity and Temperature in a Library

Books have enabled our development as a species. They contain vast amounts of information from both the past and the present and thus they must be preserved for future generations. Storing books for long periods of time requires environmental monitoring as they are vulnerable to damage in improper conditions. Read this article and get familiar with one of the best solutions for monitoring humidity and temperature in a library.

According to the Northeast Document conservation center:  

“Control of temperature and relative humidity is critical in the preservation of library and archival collections because unacceptable levels of these contribute significantly to the breakdown of materials.” 

Books are made of different materials that can deteriorate easily. The materials are vulnerable to improper temperatures and relative humidity levels. There are also other factors that play a major role in the well-being and longevity of a book.

In this article, I will go through the basic factors that you need to pay attention to, to ensure your books’ well being in the long run.

Old books in a wide bookshelf. Their condition will stay good if they are in proper humidity and temperature.
Books can remain readable for centuries if stored properly. Photo by Matteo Maretto

What are the best environmental conditions for books?


Whether you are storing books in a home library or managing a large collection of historical books in a public or a university library, you should monitor your environmental conditions. By conditions, I mean the correct range of temperature and humidity levels.

What is the ideal temperature for book storage in a library?

The ideal temperature for your books is a little under 21 °C or 70 °F. The speed of deterioration doubles every 10 °C or 21 °F, so the storing environment of books should not reach temperatures above the ideal temperature of 21 °C or 70 °C. 

On the other hand, keeping books in colder temperatures can possibly damage them when you take the books out from the cold storage to usage. This is because books are fragile against fluctuations in temperature, and if they are stored in colder temperatures than our normal living temperature, they will warm up when we are handling them. This will cause warps and other stresses on the materials from which the books are made.

What are the correct relative humidity levels for book storage?

The ideal range of relative humidity for book storage is between 30% and 55%. As with temperature, the humidity should be less than the maximum amount of 55% as high relative humidity levels are more harmful than low relative humidity levels.

Higher relative humidity levels provide the right conditions for mould or insects to thrive, which decompose or eat books quickly. Also, high humidity will speed up chemical processes that are harmful for books.

Extremely low humidity on the other hand, can lead to desiccation and embrittlement of some materials, shortening the lifespan of a book.

Colorful books in a bookshelf. Similiar sized books should be placed next to each other.
Books come in all shapes, sizes and ages. Photo by Jason Leung

Fluctuations in temperature or humidity are dangerous for books

Once you achieve the above-mentioned conditions, it is wise to keep these conditions stable. As books absorb and release moisture and temperature easily, their well being can be affected permanently by rapid changes in temperatures or humidity.

Keep books next to interior walls, as changing outside air conditions can cause fluctuations close to exterior walls. Also, books should be kept far from heating or moisturising elements, as they can significantly change the air conditions close to them.

It is hard to figure out proper conditions without any helping devices. This is why a library should invest in an environmental monitoring system to ensure correct conditions at all times.

Environmental monitoring in a library

Books require steady and correct conditions at all times in order to maintain high quality for as long as possible. Monitoring their storage, is an easy method for libraries to preserve materials as they do not need to fix tainted books or larger collections that could be otherwise completely lost. This especially applies to antique or rare books, which cost a lot of money and may be impossible to replace.

Ruuvi offers one of the best book monitoring systems for libraries. Ruuvi is a Finnish company that produces solutions for environmental monitoring in a wide range of conditions. Their Bluetooth sensors are accurate, easy-to-use and come with a battery that has two to three years of life.

Environmental monitoring in a library of university of Turku.
RuuviTag can be placed inside any library or a container

These sensors also work with the Ruuvi Gateway, which is a device that listens to the Ruuvi sensors’ measurement broadcasts and uploads them to the Internet. You can easily monitor multiple locations at the same time, read their data from selected time periods and receive custom alerts if the conditions fall outside their proper limits.

Armed with this data, you can easily adjust the conditions back to their correct levels. You may also install an air humidifier, a heating element or a little fan to be able to quickly respond to environmental changes in your library. You can read more about Ruuvi’s products on our website.

A Ruuvi Gateway listening to humidity and temperature measurements in a library.
Ruuvi Gateway updates library measurement data continuously to the internet

Environmental conditions are dependent on each other

Changing temperature changes relative humidity and vice versa. Adding some ventilation, for example, may have a larger effect than you would think. This is why an all-round environmental sensor is best for measuring storing conditions, as it shows all the measurements at the same time.

By paying attention to only one variable, you could potentially cause even more harm than in original conditions. For example, decreasing the temperature may increase relative humidity to damaging levels and mould could start to form on the books.

Graph of temperature taken from the Ruuvi Station web page.
Graph of humidity taken from the Ruuvi Station web page.
Two screenshots from the Ruuvi Station application. You will notice that the highs in the temperature graph correspond to the lows in the humidity graph.

To recap, the optimal environmental conditions for long term book storage are as follows:

  1. Temperature should be 21 °C or 70 °F
  2. Relative humidity should be 30% – 50%
  3. When storing books long term, the environment should be dark.

Easy tips to protect books for everyone

When you have a stable environment with the correct temperature and humidity levels, you can start to pay attention to other important factors. These factors are related to the ways in which books should be stored and handled.

1. Protect books from light

Keep books away from direct sunlight, as it harms paper quickly. Furthermore, keep books away from artificial light as well! Even though the radiation from artificial lighting is not as harmful as from the sun, prolonged exposure over long periods of time can cause serious damage to books.

Store books in dark rooms, when they are not used.

2. Store small to medium sized books vertically

Store books vertically so that the books that are upright and straight. Other books or bookends should help to keep the books upright, which is the least harmful for the spines of the books. Do not let books lean on each other! Keep books that are the same size next to each other for support.

Also, books should be placed firmly next to each other, but not so firmly that it would be hard to take one book from the shelf.

3. Store bigger books flat on their side

Keep bigger books flat on their side in stacks of two or three books. Do not put vertically and horizontally stored books on top of each other.

4. Leave some room on both ends of book shelves

Leaving a bit of room in front of the book line helps you to notice the dust building up and droppings that could indicate insect activity. A few centimetres or an inch is enough.

Likewise, leave some space behind the books to encourage air movement. This prevents moisture from accumulating behind the books, which is harmful.

5. In long term storage, keep books in proper air tight plastics containers

Plastic containers are great against insects and fluctuations in the environment. Remember to keep the container in a dark room with stable conditions, so that the air inside the container does not change.

Do not wrap books in basic household plastic, such as plastic bags or garbage bags, as they release problematic chemicals in the long run. These chemicals can damage books. Plastic containers designed for storing books do not release these chemicals.

6. Dust often and keep eye on insect activity

Regular maintenance is key in book storing. Dust the books gently often and pay attention to any possible indicators of pests, as a quick intervention can save your books from a total disaster.

Books should not be taken from the shelf by pulling them only from the top.
Books should not be taken away from the shelf like this. This action will cause stress to the spine. Photo by Sonja Punz

7. Handle with care

  • Do not eat or drink while handling older books.
  • Always wash your hands before touching books
  • Do not flip a book open 180 degrees as it can break the spine easily
  • Books are meant to be read in a lap. Putting a book on a flat surface can damage the spine.
  • Pull a book from the shelf by holding the spine with two hands. Pull the book gently by applying a little pressure to the books next to the book being removed. Keep a firm hold on the whole book as it slides from the shelf. Do not pull from the top of the spine or tilt the books as it damages the spine.

Conclusions

As books are usually made from organic materials, they can deteriorate or decay easily. By paying attention to the correct environmental conditions, as well as to some basic ways of storing them, books’ lifespan can be significantly prolonged.  Monitoring environmental conditions such as temperature and humidity, libraries can ensure that their collections last in good conditions for a long time.

Investing in an accurate environmental monitoring system helps this preservation effort. Ruuvi is a Finnish company, ready to help in this process. Check out our products and services and reach out to us with any questions on how our products can help you maintain the correct environmental conditions in your library! Together we can help you preserve your books for a long time to come.

Does your library need environmental monitoring?

If you treasure your book collection, then yes, you should absolutely monitor your library’s environment. Ruuvi offers products that are made for this job. With precise measuring, easy-to-use platforms and customisable alarms, you can ensure ideal environmental conditions for your books!

FAQ
Where can I store my books?

Books should be stored on bookshelves with correct ambient air conditions or in airtight plastic containers in stable environments.

Is it OK to store books in plastic containers?

It is fine to store books in plastic containers. The containers must be made for storing and they must be kept in places where there are no fluctuations in temperature or humidity. Plastic containers offer great protection against pests.

Should books be stored flat or upright?

Small to medium sized books should be stored upright so that similar sized books are next to each other. The books should not be leaning. Bigger books that do not otherwise fit on bookshelves can be stored flat on their side. Do not stack more than three books on top of each other.

Can dust ruin books?

Yes it can. Dust contains acidic elements which can cause damage to books when left alone. Dust also builds up over time so that if books are not dusted regularly, the possibility of damage will start to increase. In addition, dust can harbour tiny pests and mould spores.

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