Have you ever walked into an old library and all you can do is take a deep breath in to absorb that musty, sweet yet slightly grassy smell? That scent is the result of chemical inside the paper, the ink used and the glue breaks down as the book ages. As this process happens, there is a release of the volatile organic compounds or VOCs that results in that cherished scent you remember from trips to your neighborhood library and old tomes unearthed from a mysterious source.

Librarians are utilizing these scents as a non-invasive detector of mold or any other dangerous degradations of valuable historical documents. Scientists were able to pin point at least 15 different VOCs that can be potential indicators that will help detect onsets of mold, dependent on the composition of the said book.

Next time you are in a traditional library, take a deeeeep breath and see what scents you can pick out! While it is difficult to pinpoint one particular compound that causes the scent, Compound Chemistry gives us a good idea of what combinations do create that old book smell. Benzaldehyde is supposed to give off an almost almond-like scent while ethyl benzene and toluene give off sweet odors. If you get vanilla, it is most likely from lignin, a chemical closely related to vanillin. It is also the stuff inside of trees that prevents it from “weeping.” Lignin is found in all wood-based paper and when it starts to break down, you get a slight whiff of vanilla floating into your nostrils. Other compounds such as 2-ethyl hexanol is said to impart a slightly floral scent.

Another plus of finding out just which chemical compounds make up the olfactory portion of a library visit is that as we, the public, have less and less access to more traditional libraries, perfumiers are able to better replicate those scents to be sold as candles, perfumes, and other smelly things.