## 1 Introduction  
The preservation of historical paper artifacts, including books and manuscripts, is vital to safeguarding cultural heritage [1, 2, 3, 4, 5]. These items embody a tangible connection to past knowledge, artistic practices, and social values, making their conservation essential for maintaining a link to history. However, due to varying materials and production techniques, books from different historical periods face diverse challenges of degradation [1, 6]. Monitoring and understanding these degradation processes is therefore critical to developing conservation strategies that extend the longevity and accessibility of these valuable artifacts. Paper degradation typically occurs through two primary mechanisms: acid-catalyzed hydrolysis and oxidative degradation [7, 8, 9]. Books made from wood pulp, especially those produced after the 19 th century, are susceptible to rapid degradation. The acidic compoundsin wood pulp catalyze the breakdown of cellulose fibers, producing byproducts like furfural, a marker of cellulose and hemicellulose hydrolysis. This degradation is associated with a significant decline in paper quality. In contrast, historical papers produced from plant-based rags, as in books from the 16 th century, contain fewer acidic components and are thus more resistant to hydrolysis. Instead, these older papers tend to degrade via the oxidation of residual lipids, releasing aldehydes like octanal and nonanal as byproducts, which serve as markers of oxidative degradation. In this study, we analyzed volatile organic compounds (VOCs) emitted from two books preserved at the Biblioteca Capitolare of Busto Arsizio in Italy (Figure 1) [10]. The first volume, a Latin grammar book by [PERSON], was published in the late 16 th century and widely used to teach noble families, with its content still relevant in some classrooms today. The second volume, a mathematics handbook published in 1860, was designed to standardize measurement conversions in post-unification Italy. The books represent distinct production materials and processes, offering insights into different degradation pathways and preservation needs. Figure 1: The two heritage books examined in this study. Panel (**A**): XVI century book. Written by [PERSON], this Latin grammar became a bestseller and was widely used by teachers instructing students from noble families. Preserved in Busto Arsizio, it remains relevant today, with examples still used in modern classrooms. Panel (**B**): XIX century book. This 1860 book on mathematical conversions, acquired at an antique market, was widely used in early post-unification Italy to standardize local measurements according to the new national system. Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) enables non-invasive VOC analysis, preserving the structural integrity of valuable documents [9]. This approach allows for the identification of compounds linked to specific degradation mechanisms, such as aldehydes from lipid oxidation and furfural from cellulose hydrolysis. The technique provides conservators and researchers with a means to monitor the chemical health of historical documents, minimizing risk to the artifacts. This study aims to identify and compare degradation markers in two heritage books from different centuries to assess their respective preservation states. Using non-invasive HS-SPME/GC-MS analysis, we analyzed the VOCs emitted from a 16 th-century Latin grammar book and a 19 th-century mathematics handbook preserved at the Biblioteca capitaloare of Busto Arsizio, Italy [9,11]. By examining specific VOC profiles, such as aldehydes and furfural, this research seeks to provide a clearer understanding of the degradation pathways affecting each type of paper, offering insights relevant to conservation science.